I was using the dozer this afternoon and I received a low oil pressure warning and the machine de-rated. The code was E360. The machine has an aftermarket mechanical gauge which reads slightly higher numbers than the numbers in the monitor - see pictures. The first two pics are roughly 1300RPM and the second two pictures are at idle. I couldn't find any obvious reason why the light would come on since the oil pressure seems reasonable. If i turn the machine off and on I'm good for about 5 minutes and it comes back. I was going to start with the sensor but it seems to be working since the pressure shows up in the monitor. Any ideas?
Can you post a machine Serial Number so we can find out at what pressure the low oil alarm comes on. How many hours does the engine have.? Has it ever been rebuilt or even repaired in any way.? What brand/grade oif engine oil are you running in it.? When was the oil & filter last changed.? E360-1, 2, or 3.?
Hi Nige, I have the serial number in my signature but I should have posted it separately. Sorry about that. Serial number DHA00678. I saw E360-1 and E360-2. The machine has around 5700 hours on it. I am not the original owner so I'm not sure of any previous repairs. I purchased it from Milton Cat about a month ago and have put about 20 hours on it so far. Before I took delivery I paid Milton Cat to do the 2000 hour service and the paperwork says they used DEO-ULS10W30. Come to think of it, the machine was being used on ~25% slopes when the message went on (two separate events). The first time the light went on I checked the oil and it was a little low on the dipstick so I topped it off. But it went on again even at full. I didn't notice and drop off on the pressure while monitoring it - but it's possible that I started looking AFTER the light was already on. I am a little suspicious that an aftermarket oil pressure gauge was installed - makes me believe this isn't the first time but I could be wrong.
I tend to agree with you and IMHO you should speak to Milton about it if you haven't already. According to the O&M Manual the engine oil should be bang on the FULL mark for operating on steep slopes. Personally I would have it anytihng up to 1" above the FULL mark for my peace of mind. Also attached the low oil pressure charts. For an E360-1 the pressure must dip below 100kPa (14.5 psi) at Low Idle (700 RPM). For an e360-2 the pressure must dip below 70kPa (10.2 psi) at Low Idle.
Just for reference, this isn't normal. From experience, when the engine oil is at the full mark on the dipstick this machine will run any direction on up to a 1:1 or 100% percent slope without the oil pressure being affected.
Is the oil pressure gauge in your photos a mechanical one or does it pluck its signal from a sensor somewhere.?
We’ve got a d6k2 that’s had a lot of harness issues. I’d go to looking for chaffed wires from the pressure sensor on down the line in the harness if it was me. That is, if in fact the pressure is not dropping on the aftermarket gauge when it throws the code.
Just an update: the machine threw low oil pressure warnings about five times today while on flat ground. The machine was fully warmed up, and both the mechanical gauge and the computer reading showed good pressure each time the code occurred. There is a difference between the digital gauge in the computer and the mechanical gauge—roughly 20%. For example, when the computer reads 34 PSI, the mechanical gauge shows around 40 PSI or slightly higher. I was able to replicate the warning once by pressing and holding the decelerator. At that time, RPMs were 1400, and the pressure dropped to as low as 34 PSI. I’m not sure if that’s technically within range, but that drop triggered limp mode. The only other thing I noticed, which seems a bit odd (and this is a new machine for me, so I haven’t used it much), is the Tattletale section in the settings. The engine oil pressure showed –3 PSI, which doesn’t seem right to me. I’m not sure what that means, but it caught my attention. At this point, I’m unsure whether switching from 10W-30 to 15W-40 oil would help. I’m also considering whether the issue might be a faulty oil pressure sensor or a wiring harness problem. That’s where things stand right now. .
Sod all that. Did you speak to the dealer yet and what did they say/do about it.?
See the low oil pressure charts I posted earlier.
Sorry Nige - I didn’t see the chart in your attachment. According to the chart, 31.9 psi or lower would trigger a 360(2) code. I hit 34 for a second and then it was 36ish and it and I still got 360(2) I’ll call Milton tomorrow to see if they’ve serviced this issue before. Thanks for the reminder.
The only service the dealer has ever done on the machine is when I purchased it. It has had service at a dealership in TX previously. I have a local mechanic looking at the machine now. He believes the sensor has been replaced. He sent an oil sample out. I did notice this afternoon that https://www.catfluidselector.com recommends 15w40 for my machine and serial number and 10w40 in colder weather as an alternative however Milton Cat used 10w30 when they did the service on the machine. I'm not sure if that is the problem but I think that's my next move. Nige, we are going through the checklist you sent earlier. I think everything on that list is palatable except a bearing issue wouldn't make me very happy
A change to a heavier grade of oil may take away the symptoms for now, but at best it’s a Band-Aid. I wouldn’t make any sort of move until you have talked to the selling dealer - see below. That’s not the point as far as I’m concerned. The dealer who serviced it most recently is the one who sold the tractor to you. To me it implies they have a responsibility that what they sold is of “merchantable quality”, in other words free of defects. I’d class low oil pressure as a pretty serious defect and I reckon it’s long overdue that you had a conversation with them, unless of course they sold the machine to you with “no warranty express or implied”, in which case you are out of luck. It’s now 2 weeks since you first posted and I see nothing yet to indicate you have spoken to them.
It has 5700 hours, it could have some weakness in oil pump , mains and rod bearings, etc. But firstly : I would after talking to dealer, get rid of that oil, change to 15W40, make sure the engine is full to correct level on dipstick plus 1/2 inch is what I have always done. I have changed out numerous oil pressure sensors on Cat skidsteers that had less hours by 3500. Not saying your sensor is done, but would take an oil sample as well incase you have fuel dilution in the oil at lower percentage but still affecting ultimate oil pressure. After dealer talk, start with the simple things. Simon C
Nige, I agree. The dozer has to work for a few hours to trigger the light so the heavier oil might band-aid the issue - but it's probably not the problem. Unfortunately the machine was purchased as-is. I did test the machine out at the dealership and it was fine. I was going to start with the sensor but there was a clip that secures the oil pressure wiring hardness to a metal bracket. That clip was undone and the sensor looks new - so someone changed it already. We hooked up a mechanical gauge to the sensory port and the readings were similar. The mechanic does seem to think the pressure is on the low side, but from what I've seen it's still higher than what is needed to trip the code. We cut the oil filter open and it was clean - but we sent the oil sample out anyway. It only has about 40 hours on it so hopefully that's enough. If the oil sample comes back clean I believe the plan is to change the oil to 15w40. If it still reads low I guess we'll run through the list and drop the oil pan to change the oil pump and pickup tube and to check out the piston cooling jets. The only item on the list that I can’t find in the parts manual is the oil pressure relief valve.
I think if it was me and it got to the point of dropping the oil pan the first thing I would be looking at would be the condition of the oil pump suction screen followed closely by the main & rod bearing shells. The oil pump would be last on the list. YMMV.
Had one with lots of similarities to yours, ended up finding intake hose clamps loose before the turbo, poor engine was slowly being dusted for years, turbo compressor wheel was razor sharp and starting to disintegrate. Then workshop pulled the engine out and found oil pump outlet tube loose. Just an FYI.
Easy enough to check and a lot simpler than dropping the oil pan.
Thank you for the advise. Unfortunately it seems likely that the problem is not an easy fix. I'm not sure if I ever mentioned this before but the oil pressure is around 60-65psi when cold at 1400rpms. When fully hot it's around 35psi. That would not be good at all. The likelihood of a big bill in my future is increasing by the day
It would be a fairly simple thing to check the security of all the clamps on the intake system. Either that, or look for silicon in the oil analysis.
Most motors when cold will have way more oil pressure than when the oil hits 200F. Its the high idle as well as low idle pressure that will tell more than anything else. Simon C
That big of a change, is not a good sign, at all.
To inspect the suction side of the intake system only requires checking the tightness of 4 clips in 3 locations between the air cleaner assembly and the turbo inlet. See the illustration below. At the same time I would suggest to look closely at the hose marked #15, and the steel elbow tube that connects it to the turbo, for any sign of splits or damage. While you are doing that open up the air cleaner assembly and remove both filter elements then, using a clean white cloth, reach down into the intake duct and wipe it around the inside of said duct. Take a photo of the clutch after you remove it and post it up. Replace the air filter elements. As I said before, pay close attention to the silicon numbers when the oil analysis results come back.
Nige, The plot thickens..... I called Warren Cat and they will not release their service records of the machine since I was not the owner at the time. My salesman at Milton Cat was able to take a screenshot showing the oil pump was replaced on June 21st 2023 when the machine had 5282 hours. The machine has 5790 now. So I guess this means you were right twice? "Check the previous service records" and "it's probably not the oil pump". This entire situation has my incredibly anxious - I'm really hoping it's not something catastrophic. But I do really appreciate your help. Stay tuned.
That puts a totally different complexion on the problem. I wonder if the mechanical oil pressure gauge was also fitted around, or before, that time.? It would make sense. It would be interesting to get hold of the Work Order AB00514 and take a look at exactly what other work was done at the same time. To my mind it would be criminal not to have pulled a couple of main/rod bearing caps to have a look.
Everything is tight and the intake tube was clean as far as I could stick my arm down it - see below. I emailed Warren Cat again to see if they could send me just that work order with the customer's information redacted.
Everything tight - check. Air inlet duct clean(ish) - check. I think that unless the oil analysis comes back with indications of a huge amount of silicon then the engine does not appear to be dusted. That has to be (somewhat) good news. Did you check the flexible hose and the steel elbow for any signs of cracks/splits/damage.?
In addition to Nige's question... Just for the record, with the engine warmed up to normal temperature, and looking only at the aftermarket gauge, have you at any time noticed the oil pressure drop below the trip point in the graph below? See psi in red, kpa hurts my brain.
Just a thought. If Warren Cat will not give details of that Work Order to you can the dealer who sold you the machine get access to the information it contains.?
At 1400rpms it does occasionally drop below 36 for level 1. For level 2 I believe the limit was 32psi. I’ve never seen it drop below 34 but at some point it does trigger the level 2 code when I hit the decelerator. I just spoke to them and the admin is waiting for approval to release the work order. My salesman is also willing to reach out so I think I will get it eventually. See oil analysis (and the last 2 from Warren Cat when the oil pump was changed)
Silicon is in single figures which appears to confirm that the engine is not dusted. Bad news is the 4ppm of lead. Lead should generally be either zero or 1, it often fluctuates between the two. For me 4ppm of lead points pretty conclusively to crankshaft bearings, despite the overall analysis result interpretation of the most recent sample being Green. What you have to also bear in mind is that the most recent sample only had 31 operating hours on the oil, so that level of lead at only 15% of the planned oil life is nothing short of catastrophic in my view. I would look sideways at 4ppm of lead at 250 hours on the oil, let alone 31. Also consider that the two previous samples were taken a few days apart but both were with 0 hours on the oil, so they don’t really indicate anything. The oil sample that would have given a clue would have been the one that was drained from the engine when the oil pump was replaced, but that one obviously got thrown out with the bath water….. Time to get the oil pan down for a sticky beak I reckon.
Service records from Warren Cat. Well this is pretty unbelievable lol
As regards where to go from here my vote is still to drop the oil pan as a first step. At least Warren did the right thing and replaced the main & rod bearings at the same time as the oil pump. Even cranking on the starter with cold oil should develop something around 10psi I would have thought. Strange that the pressure hardly registered. I don’t know what the oil system on that engine uses as a high oil pressure relief valve and right now I can’t find out. A leaking HP valve could lead to low oil pressure because a percentage of the flow is bypassing back to the oil pan. Maybe someone else knows.?
I don't know either on that engine, but have seen some that have 2-3 oil pressure reliefs on them and any one could be partially open, or opens at too low of pressure. Simon C
I recall we had a lot of issues with the pressure relief & plugged oil filter bypass valve system on C13 engines. The valve poppets in both were plastic, the housings were aluminium. Over thousands of hours wear took place in both the poppets & the housing leading to engines throwing low oil pressure warnings at idle speed when full warmed up as it came close to engine oil/filter change time. Fresh oil was a Band-Aid, the long-term solution was to replace the complete assembly which was part of the oil filter base.
Just so I'm not missing anything - here are the possible causes from the diagnostic sheet: 1. Engine oil level: No – it’s ½” over full. 2. Oil specification: No – it was just changed by the dealer. 3. Aerated oil: No visible signs of aeration. 4. Oil pressure sensor: Not likely. It was already replaced and it was verified with a mechanical gauge 5. Engine oil filter: No. It has been replaced twice in 40 hours. One was cut open and was clean 6. Engine oil cooler. I have not looked into this but Warren Cat claims to have inspected this 400 hours ago. 7. Fuel in the oil: No per sample 8. Piston cooling jets: Most likely not the issue. These were inspected by Warren Cat 400 hours ago. 9. Engine oil suction tube: Not yet inspected. The oil pump was replaced 400 hours ago. 10. Engine oil pump pressure relief valve: I cannot locate any information on this but I believe this might be built into the oil pump which was replaced 400 hours ago. 11. Engine oil pump: Not likely. Replaced 400 hours ago. 12. Bearing clearance: Crankshaft and connecting rod bearings were replaced. Camshaft and idler bearings have not been inspected. There really aren't many possibilities as I see it. Camshaft and idler bearings? Maybe the oil pump or suction tube was installed incorrectly or came loose? Do you know if the piston cooling jets have check valves or anything else that could be stuck open? or are they just tubes that flow oil through them at all times. I'm at a loss where to go with this - and so is the local mechanic.
The strange part is that the oil pressure is great when cold - it's only a problem when its warm. If a pressure relief was stuck, wouldn't it be low at all times?
There will be a pressure relief valve in the oil filter housing most likely, There could be a secondary one in the pan off of the main pump that would not of been replaced with the pump. There could be some kind of pressure valve in the oil cooler. None of these can I verify for sure, as I don't have a manual on it, but have seen all these on different machines before that had to be checked out. Simon C
I built a D155A-1 engine that was in 10 pails and not one bolt marked on it. Had to figure it all out. Missed only one thing a 3/8 plug in the bottom rail of the block hiding up in a hole. Still had good oil pressure when cold was low by 3 pounds when hot. Pulled a side cover of the pan off and looked with flashlight and mirror and oil problem fixed. So much oil pressure we could not believe. What your problem could be will take a diligent look at lubrication system in overhaul manual to see if something was missed. Seen a Cat 3408 that had a 3/8 plug missing in front gear train that only had low oil pressure at high oil temperature. I found a Detroit 4-53 with four plugs missing in the bottom of the rod bearings and still lived 500 hours each time before scuffing the cylinders. You will need info before coming to any conclusion. Simon C
I see where you’re going Simon, but all your examples above are from engines after a rebuild. To me it appears as though on this engine the low oil pressure was already there before the oil pump and the main/rod bearings were replaced. Let’s face it nobody is going to go into an engine on a whim replacing parts just because. I think that something else in the lubrication system is likely the cause of the low oil pressure but without access to all the information regarding exactly how the system operates I don’t even have a place to start. It’s a possibility that something in that engine has been “wrong” ever since it was originally built. e.g. an orifice somewhere that was missed on original assembly but when the engine was new the clearances would all have been tight enough that the “deficiency” in oil pressure would not show up in a dyno test and the numbers, although maybe a bit on the low side, would have still been within the “acceptable” range. @gcsupraman - Can you ask your salesman if he can talk to the Tech Communicator in the Service Dept and get hold of the original factory dyno test results for the specific engine S/N installed in that tractor.? It would be interesting to see the oil pressure numbers when it was new/zero hours.
Not necessarily IMO. A worn pressure relief would bypass much less with cold thicker oil than it would with oil at normal operating temperature which would be significantly thinner.
I agree that after 5000 hours the oil problem will have shown itself up a long time ago, unless a plug fell out suddenly, but as I said before there will be a relief valve hiding elsewhere that is where I would look first. And yes a relief valve stuck just a little will show perfect oil pressure until the oil hits 200F plus in temperature and then it is dropping. External oil filter housings without taking off the pan would be a good first start. Simon C
Agreed. Say there’s a score in the valve or seat? Or a broken spring? Cold thicker oil will still take more pressure to get by it the same as cold oil makes more pressure to get through all of the passages in an engine in perfectly good health. In all honesty, cold oil in a perfectly good engine is probably blowing a relief partially open until it warms up some and the viscosity drops. There’s a chance that you have a relief that is relieving around the normal amount cold but not closing all the way once the oil is warm and the viscosity is down to normal operating range. I’ve been slammed lately and haven’t had a chance to look up your machine on sis. Anyone have any idea if there are for sure more reliefs in the system outside of the one in the pump? From what I remember reading, it made it past 5,000 hours before oil pressure complaints arose?
Appears I was typing when you replied.
I have yet to see one that did not have an extra relief valve hiding elsewhere other than in the pump. But I have been wrong before, but a good lubrication system schematic would show it all. On the SIS is my guess. Simon C
The lead in the oil samples, could they be that high because the bearings are still breaking in? I like the original suggestion, of running the thicker oil and not looking at the oil pressure, when it’s warm. Seems this particular machine, has been traded in, with this ongoing issue and you ended up with it. Run the 15/40 and put a few bottles of Lucas oil conditioner and use it.
From everything I know lead numbers do not increase even during break-in. I will check though and revert. It’s also worth pointing out that the new oil pump was fitted long ago so any break-in should have taken place way back. In an engine that size the break-in period is going to be a couple of hundred hours at most. This engine has gone 600+ since the oil pump replacement. I wouldn’t recommend that personally. IMO it’s the equivalent of sticking your fingers in your ears and repeatedly singing “La La La La La La La” in a loud voice in an attempt to drown out someone who is attempting to communicate some less-than-welcome news. My 2c. YMMV.
Wanted to mention that a relief valve that is stuck open a hair will wear out the seat or the spool, which ever is weaker in time. They can be leak tested when off such as a filter housing relief if it has one. Never know when you will find a broken spring or jammed open spool in relief. Simon C
I purchased the machine used but that's what I've been able to determine so far. Major repairs were performed around 5300 hours to try and solve the problem including new main bearings, rod bearings and the oil pump (and pressure relief valve). At some point the oil pressure sensor was replaced as well. I've tried to find another relief valve in the SIS parts lookup. I've searched, looked at all the lubrication schematics and haven't been able to find anything. In the oil filter housing there could be a bypass Here is the oil filter housing. I don’t see any valves - it’s pretty basic. Is this the oil cooler? Maybe I’ll pull that off and peak.
Ultimately, that’s probably the direction I’ll go. I plan to pull the oil pan and check for anything obvious. While I’m in there, I’ll likely replace the oil pump and pressure relief valve again, hoping the valve may have been defective. I’ll also take another look at the piston cooling jets. After that, I’ll put it back together and try running 15W-40. I’ve been using the machine more, and I’ve noticed that as long as I avoid hitting the decelerator when the engine is fully up to temperature, the low oil pressure warning doesn’t trip. That makes me think a slightly heavier oil might increase the pressure enough to work. Beyond that, I’m not sure what other options there are short of eventually purchasing a long block. I've had pretty good luck buying used equipment but my streak is over with this machine
Before you make a decision, maybe wait until Nige's SIS is back in action and then maybe he will find the Lubrication operation info that will show all the relief valves and anything else of interest. I have seen other relief valves that were right in the middle of a discharge pipe coming off the pump, don't know what there is hiding in your machine. Simon C
Nige asked me to comment. Couple things stand out in the most recent SOS. 4 PPM lead should be accompanied with tin, but tin is zero. Next, lead usually shows up in a 4:1 ratio with iron and/or copper. It’s more like 2:1. That makes me think this lead is a chemical thing vs a mechanical issue. The dealer may have washed the oil cooler when they inspected it. Thus, the lead solder in the cooler bundle might be leaching. The mechanic may have used an assembly lube containing lead, or a snake-oil type additive may have been added to the lube oil at some point. I’m convinced it’s a chemical contaminant. Not wear. But, it’s just one sample, so who knows? Sorry to hear about this mess. How frustrating.
Glad you joined this. I don’t have much for interpreting skills with these samples. Our cat dealer has gps hour meters in our machines and does the services for us. I get the oil sample results but generally take them with a grain of salt. If it’s raining, the sample has water in it. If it’s dirty, silica is high or large particle count is high and so on. Oil samples are only as good as the sampler I figure. Very valuable addition to the arsenal if used properly and interpreted by someone schooled up on it but if all of the variables are not known, go at it with an open mind and check all of the simple stuff first. Maybe pull your own sample keeping all of this in mind too. I don’t trust them unless I’m the one that pulled it.
For me oil sample results interpretation is primarily about looking at trends, and in the case of this engine there are nowhere near enough results to establish a trend of any kind.
Try searching for 2772504. It should come up as a cooler group. If you find it please post an image of what it shows.
I just activated the service and repair side of SIS2GO which includes the removal instructions for the oil cooler so I should be good to go with investigating that. I didn't see an "oil pressure valve" listed in the parts lookup for the oil cooler, but there also isn't a pressure valve listed separately for the oil pump so that doesn't mean there isn't one.
I just wanted to take a moment to thank everyone who’s helping. This situation doesn’t seem to be straightforward, and it’s definitely leaving me feeling a bit unsettled, for lack of a better word. I really appreciate all of your efforts and support - it means a lot. -Greg
I don’t see anything either. Are there any breakdowns of Items Ref #5 and #9 by any chance.?
If it has a relief Valve, 5H is the bore that would contain one, but maybe it has none. Some engine oil pumps discharge straight into the block but some have a pipe feeding to back end of block with a relief valve built into a Y on the pipe. Yours may be straight into the block, haven't seen a picture yet. You will get it figured out yet. Simon C
There isn't a picture, or a link to click on to get more information so I don't believe so. What you're saying makes total sense. Essentially it could be a situation similar to the oil pump where there is a pressure relief or bypass valve built into the cooler that doesn't show as a separate part and pressure could be bleeding off. There is what appears to be a NOS Oil Cooler on EBAY with very clear pictures: Caterpillar 295-8610 I'm thinking of just purchasing it since I'm going through the trouble of taking it off the machine anyway. Thoughts? Here is what AI is suggesting based on the previous repair history and all the comments in this thread so far: 1. Mechanical gauge first to confirm pressure and rule out sensor/wiring issues. (done) 2. Drop the oil pan and inspect pickup tube, pickup O-ring, pickup bolts, and screen for cracks, looseness, or restriction (a suction leak can cause good cold pressure but low hot pressure). 3. Inspect oil pump again even though it’s new—check pump housing, gear wear, and especially the pressure relief valve for leakage or seat damage. Might be better to just replace it (cheap insurance) 4. Verify piston cooling jets are tight, not cracked, and none are missing (a loose or missing jet becomes a major internal oil leak). 5. Inspect the oil cooler for internal leakage or bypass issues. 6. Check oil gallery plugs in the block for looseness or missing plugs. 7. Check for front cover internal leak 8 . If all that checks out, the camshaft bearings could be bleeding pressure internally when hot. Remove the oil filler cap and look inside with a flashlight to check for excessive oil flooding in the valve train which can validate cam bearing leakage. Cross your fingers this isn't the problem Pressure numbers (50 cold idle/ 16 hot idle / 36 at 2000 rpm) suggest the pump is functioning but oil is bleeding off somewhere rather than total engine wear. My Milton Cat salesman who's been trying to help got stonewalled by service - essentially they won't assist me until the machine is in the shop. They are working on a quote for a long block though lol
On point 4 --- If a piston cooling jet was missing you would have a destroyed cylinder and all kinds of parts in pan. Point 8---- If the camshaft bearings are all gone the cam would be producing a lot of copper from my experience. That was not the case with your sample. Check the simple things before going into any kind of big dollar items. Simon C
I poked around on sis and came up with nothing to add. They do not list any oil pressure reliefs separately as you have already found. Or any form of a schematic for the lubrication system. About just going to have to go exploring.
Can you find the SysOp document for the engine lubrication system and upload a pdf copy to the thread.?
I ended up just doing the copy/paste thing but this is all I could find…. Oil pressure for the engine lubrication system is provided by an engine mounted oil pump. The engine oil pump is located on the bottom of the cylinder block and within the oil pan. Lubricating oil from the oil pan flows through a strainer and a pipe to the inlet side of the engine oil pump. The engine oil pump is driven from the crankshaft through an idler gear. The engine oil pump has an inner rotor with four lobes. The inner rotor is mounted to a shaft which also carries the drive gear. The engine oil pump also has an outer annulus with five lobes. The axis of rotation of the annulus is offset relative to the rotor. The distance between the lobes of the rotor and the annulus increases on the right hand side when the rotor is rotated. The increasing space between the lobes of the rotor and the annulus causes a reduction in pressure. This reduction in oil pressure causes oil to flow from the oil pan, through the oil strainer and into the oil pump. The distance between the lobes of the rotor and annulus decreases on the left hand side when the rotor is rotated. The decreasing space between the lobes of the rotor and annulus causes oil to be pressurized. The increase in oil pressure causes oil to flow from the oil pump outlet into the engine lubrication system. The oil flows from the pump through holes in the cylinder block to a plate type oil cooler. The plate type oil cooler is located on the left hand side of the engine. From the oil cooler, the oil returns through a drilling in the cylinder block to the filter head. The oil flows from the oil filter through a passage to the oil gallery. The oil gallery is drilled through the total length of the left side of the cylinder block. If the oil filter is on the right side of the engine, the oil flows through a pipe assembly. The pipe assembly is mounted to the lower face of the cylinder block. Lubricating oil from the oil gallery flows through passages to the main bearings of the crankshaft. The oil flows through the passages in the crankshaft to the connecting rod bearing journals. The pistons and the cylinder bores are lubricated by the splash of oil and the oil mist. Lubricating oil from the main bearings flows through passages in the cylinder block to the journals of the camshaft. Then, the oil flows from the second journal of the camshaft at a reduced pressure to the cylinder head. The oil then flows into the rocker arm bushing of the rocker arm levers. The valve stems, the valve springs and the valve lifters are lubricated by the splash and the mist of the oil. The hub of the idler gear is lubricated by oil from the oil gallery. The timing gears are lubricated by the splash of the oil. The turbocharger is lubricated by oil via a drilled passage through the cylinder block. An external line from the engine block supplies oil to the turbocharger. The oil then flows through a line to the oil pan. Piston cooling jets are installed in the engine. The piston cooling jets are supplied with the oil from the oil gallery. The piston cooling jets spray lubricating oil on the underside of the pistons in order to cool the pistons. PCP-000210EA 2026/04/02 20:48:16-07:00 i02413834 © 2026 Caterpillar Inc.
The relief in the oil pump is mentioned in the troubleshooting steps for low oil pressure but that is the only one mentioned.
See the statement regarding oil flowing at reduced pressure from the camshaft to the valve gear.? I assume that would be through some kind of orifice which by design would keep the oil pressure to the crank/camshaft high(er).? I wonder where that is located.? I don’t know if the engine is in a running condition right now but it might be interesting to pull off the valve cover and see how much oil is arriving to the valve gear. It might even be possible to see something via the fumes disposal connection or whatever other caps might form part of the valve cover.
Nige filter relief ?valve
Like you suggested, I could probably get a view if I remove this breather. I have my car so I don't have any tools with me, but i'll be back tomorrow and i'll report back. PS I'm not sure why the picture isn't embedding - sorry! View attachment IMG_7195.jpeg
TBH I have no idea what would be classed as an excessive flow of oil to the valve gear but maybe it might become obvious that something is not right once you look at how much oil is flowing up there.
I was using the machine this morning and just wanted to add some information. Morning start (46°F): Idle oil pressure was about 59 psi. After ~30 minutes of light running: Idle pressure dropped to around 22 psi. The machine wasn’t really working hard. Previously under heavier work (pushing big piles, etc for extended periods of an hour or longer.): I've seen the pressure drop as low as 16 psi at idle I started thinking about oil temperature. Would knowing the oil temp help narrow down possible issues? Hypothetically, is it possible the cooler could be bypassed by a bad internal relief/bypass valve and the oil is running so hot that it’s too thin?
Knowing the oil temperature might be very useful. Perfectly possible that the cooler might be somehow bypassing. The thing about diagnostics is that potential issues are eliminated one at a time until what remains, however unlikely that might be, must be the cause. At this point it’s wrong to rule out any possibility IMHO.
Drive train gear bushing.
Do you mean the idler gear in the front gear train.? An illustration of the front gear train setup might be useful. “The hub of the idler gear is lubricated by oil from the oil gallery. The timing gears are lubricated by the splash of the oil.”
Idler gear, Ive seen it on more than a few cat engines over the years the bushing wears and dumps the oil . I dont know this engine but ive seen the same complaint over the years and several times it was the idler gear bushing.
Oddly enough that is listed in the service diagnostics that Nige posted and is one of the only things that hasn't yet been inspected.
Ok… so here’s where I’m at. I replaced the oil cooler — that was a pretty frustrating process, but I’ll save that story for another time. Unfortunately, there was no change in oil pressure. After taking a closer look at the old cooler, I don’t see any kind of bypass valve. It looks more like those plugs are just from drilled passages, but I could be mistaken. One thing that stood out to me is the difference between the manual gauge and the factory oil pressure sensor — there’s about a 25% difference between the two. The manual gauge is tapped off the oil filter housing, but I don’t have a clear reference for where the factory sensor is located in the circuit. To me, that suggests the pressure loss is happening somewhere after the oil pump, pressure relief valve, oil cooler, and oil filter. If I knew where the sensor was that could certainly narrow it down. I also pulled the vent to try and get a look inside the valve cover. Visibility was limited, but it didn’t appear like the valve train was flooded with oil. It definitely wasn’t overflowing or draining back through the crankcase vent. So now I’m at a bit of a crossroads. The oil pump and pressure relief valve seem to be doing their job, since pressure at the filter (per the manual gauge) looks good. That leaves things like the idler gear bearing or camshaft front bearing — neither of which are simple fixes, and beyond my abilities. By the time you factor in transport both ways, I’m guessing I’d be somewhere around $10,000 at the Caterpillar dealer just to replace those. The local mechanic is suggesting a long block because it's a guaranteed fix— about $19k from the dealer on SIS, so I'm guessing $30k+ installed but that's just a guess. I could pull the oil pan but since the pump and relief valve seem to be working I'm not sure what I would be looking for. Does anyone have anymore ideas? Otherwise, this is my next move.
I can see about 9 pounds difference between the 2 gauges. Maybe the sensor that reads the pressure is partially plugged with dirt, or the wires from it need to be load tested incase the signal is not strong enough to be accurate. I would be prone to try one second mechanical gauge and figure out why the electical end is reading incorrectly. Don't know where the sender is but Nige may be back in action shortly and he would have it for sure. Simon C
That's a substantial difference from ecm value to actual.
Okay, so I had a mechanic come out about two weeks ago. From what I understand, they hooked up a mechanical gauge to the same port as the oil pressure sensor, and the reading was close. According to them that confirmed the sensor itself is working correctly. He explained that readings can vary slightly depending on location — for example, a mechanical gauge at the oil filter versus a sensor reading from an oil gallery in the block — but when their mechanical gauge was connected directly to the sensor port, it was close. At some point prior to my ownership the sensor had already been replaced as well. I didn’t see them test it personally but this is what I was told. I could try to test the wires but I might need some help.
I wouldn't spend a dime until that oil pressure sending unit's wiring was load tested in case that is the problem. Unfortunately, I checked all my schematics and do not have yet anything for your machine. Nige will have once his program is back in action. Might be anytime soon I believe. Could be a simple repair in the end. Simon C
Does this help at all?
Still not ready as at close of play today. Hopefully Monday, fingers crossed.
The thread makes some unpleasant reading and a reminder of the stress that these issues can give a man. I’m wondering if there’s an issue in the suction lines on the pump or something fractured in the oil gallery somewhere. Clutching at straws for sure,but I was given a right royal run around with an elbow fitting on the oil rifle on a Cat D342 D8H motor,not to mention a head banger of D9R transmission suction pipe that’s factory fit only. Flared flanges in steel pipes and D9R’s are a thing of lost sleep to this day.
I posted the wiring electrical schematic off the SIS2GO app. I was thinking about your comment this morning, and I do recall the mechanic saying that he saw some oil inside the plug of the pressure sensor. He said the pressure sensor looked new and it was probably caused by the previous sensor leaking oil. Can residual oil inside the harness skew the voltage readings to the ECM. The only other thing that I thought was odd (and I still can't explain it) is that the machine appears to trigger codes 360(1) and 360(2) when the screen is showing pressure above the thresholds. I need to pay closer attention. Is it possible to install a tee so I can use the sensor and the manual gauge in the same port? Unfortunately this problem is literally all I think about if my eyes are open
I am a bit confused. A few posts ago you mentioned that you were not sure of the location of the oil pressure sensor but the mechanic obviously knows where it is. Why not ask him.? Next thing is that if there was oil in the connector, allegedly from a previous sensor failure which is entirely possible, then why didn’t he get in there with contact cleaner and remove it all.? It’s possible that the sensor signal could be affected by oil in the connector and you need to remove all doubt. As a first step I would suggest to clean out the oil from both the end of the sensor and the harness connector to eliminate any possibility of the signal being affected. At the same time the sensor could be removed to identify the thread on the end of it and look at the possibility of installing a tee at that location to connect a mechanical pressure gauge to confirm the sensor reading.
Here is the location of your Engine oil pressure sensor. Get it apart and wash it out as Nige said. Will post the wiring from it to the ECM shortly, super easy to follow wires on schematic. Simon C
Sorry forgot to say it is item 14 in both views. Simon C
Agreed. Each wire is marked with a number as well as a colour. It couldn’t be much easier.
Here is the wiring from the Oil Pressure Sensor Item#14 to the Engine Computer pin outs. Three wires to check from one end to the other with a 5 amp bulb. First Disconnect your batteries carefully and cover the posts so nothing can happen like a big spark. Next hook up a 5 amp Test light to one wire at the sensor plug with the plug disconnected and the computer plug disconnected also. Your 5 amp light can now be connected to any 12 volt battery or to one on the machine, and connect the other end of the same test light to Any one of the 3 pins on the Sensor connector. Which ever pin you pick follow that pin to the ECM same wire number and hook that pin to the test batteries ground. Leave it on for 10 minutes to make sure that it does not start to fade out when or if the wiring gets hot. All 3 wires are done the same way. Be a good idea to take a picture of the schematic picture I posted with your phone to have at machine along with the instructions. Easiest Schematic to follow. If the mechanic says this is too complicated, run the other way from him. Be careful to not damage any plug in pins especially at computer plug. Simon C
Forgot to mention to NOT use anything like Die-Electeric compound on any of the connections. Simon C
Nige, maybe I misspoke but I believe I mentioned I didn't know where the oil cooler was. I know where the sensor is. I purchased an oil pressure test kit today which contains many adapter fittings. Once I figure out what fitting is needed for the block I will purchase a tee and then move the mechanical gauge from its current location in the oil filter housing to the tee so both the factor sensor and the manual gauge are reading from the same circuit. Thank you. I have a test light so I will complete this on Tuesday or Wednesday. OOPS. When I replaced the oil cooler I used die-electric grease on all the electrical connectors when I re-assembled everything. I will use contact cleaner and an air compressor to remove.
Do you have a better closeup photo of the oil pressure sensor.? Maybe also one of the connector unplugged so we can see what it looks like inside. Maybe also check the Part Number if the sensor against the 278-5225 Part Number marked on the electrical schematic.
It was a somewhat productive day. Sorry for the lenthy post. I removed the factory pressure sensor and hooked up the oil pressure test gauge I picked up over the weekend. The goal was to compare pressure readings using the test gauage installed in the factory sensor location to the manual gauge currently installed at the oil filter housing. It does appear that pressure at the filter housing is higher, but to confirm that definitively, I need to swap the gauges and retest under the same conditions. More importantly, the pressures I previously recorded from the factory sensor were consistent with the readings from the mechanical test gauge installed at that same port. The factory sensor uses an M12 x 1.5 thread while the previously installed manual gauge and the new test gauge are 1/8" NPT. I ordered an M12 x 1.5 tee with a 1/8" NPT port so I can install the manual gauge directly at the factory sensor location and compare readings more accurately. Per Nige’s recommendation, I checked the part number on the sensor and found that it is NOT the correct one. While it matches in form and fit, it is not listed as the proper application for this machine. Part number 278-5225, on the other hand, is specifically identified as the correct oil pressure sensor. I did not see any cross reference but maybe I missed it. Initially, I thought Nige helped find the issue, but since the actual pressure readings seem to align with what the sensor is reporting, I'm not 100% sure. In an earlier post (#84), I noted something that still doesn’t make sense: the machine is triggering codes 360(1) and 360(2) even when the displayed oil pressure in the computer appears to be above the threshold values. These faults are supposed to require the pressure to fall below the minimum limits for approximately 8 seconds, but I have not observed the pressure dropping below those limits when the codes are set. I put together a chart comparing readings from the factory sensor, the installed manual gauge, and the test gauge. I included the minimum pressure thresholds required to trigger 360(1) and 360(2) at various RPMs. Based on what I’ve seen so far, the data doesn’t clearly explain why the codes are being triggered. I still plan on testing the wires tomorrow but I'm assuming my next move would be to order the correct sensor
What Part Number of sensor did you find installed.? The 278-5225 may well have been replaced by a newer Part Number that SIS does not show. I would suggest that in the first instance you should contact your dealer parts department, give them your machine Serial Number and ask THEM to tell YOU what is the correct Part Number for the oil pressure sensor. What did you find (or not as the case may be) in the way of oil in the electrical connector.?
I put everything in the attachment with pictures. There was some oil in the connector when it was removed two weeks ago but it was suspected that oil was from the old sensor. I’m going to clean everything out and test the wires on Thursday. After some initial excitement, I'm now wondering if they are the same part with the exception of the o-ring included on the oil sensor. I’m going to call the dealer to ask them to pull 278-5225 and check the writing on the plug.
Wasn’t it cleaned out at that time.? If not then you should clean it out now and run the engine for a while to see if any fresh oil appears in the end of the sensor. It does appear that 278-5235 includes the O-Ring but best to check with the dealer what the sensor part number is, even if only to rule it out as a possible cause.
I called the dealer—278-5225 is a kit that includes the 274-6721 sensor with an O-ring, so that ended up being a dead end. Today I isolated and tested all three wires. Each one powered the test light without any issue, and all showed zero resistance on the ohm meter. I verified the ground wire against the frame with the ECU plugged in, and that checked out as well. I also checked for any voltage bleed between the wires, and found none. I cleaned out the sensor connector, but ran out of time after dropping a socket and having to pull the skid plate—always a good time. I did get the tee fitting today, but I’m not completely sure it’ll work in the block due to the shape of the factory sensor. I’ll find out tomorrow. At this point, I’m debating my next move. I’m thinking of pulling the pan but I’m not expecting to find anything. If I knew it was the idler bushing or the cam bearings I would have them done - but I don’t know for sure it’s very expensive to explore that possibility. The machine will run without the sensor plugged it. It throws a code but if it doesn’t derate that might be an option. Or I’m sure I could also find an 1/8 to m12 adapter to relocate the sensor to the filter housing where the pressure is higher….but both of these don’t fix the problem and I’d prefer that. View attachment IMG_7300.jpeg
Just an update on the oil pressure issue. I was able to install a T-fitting and run a mechanical gauge at the same location as the factory sensor. The readings now match almost perfectly, which confirms the factory system is accurate and rules out any sensor or wiring issues. On the downside, the pressures are consistently on the low end of acceptable. To try to improve things, I changed the oil from 10W-30 to 15W-40 and added a Lucas oil conditioner that was suggested to me. I know this isn’t a permanent fix, but with the current workload I needed to do what I could to keep the machine running for now. After the oil change, I saw an improvement. Hot idle pressure went from about 16–17 psi up to around 21 psi, and overall pressure is up roughly 10–15% across the board. I ran the machine for a good portion of yesterday under load with no issues. So far, it appears to be a workable temporary solution while I plan the next steps. When things slow down, I’m planning to drop the pan and inspect for anything obvious, but for now this at least keeps the machine operational during a very busy period. View attachment IMG_7305.jpeg
So that confirms an internal engine problem somewhere. Only one suggestion. Make sure that nylon hose for the mechanical gauge is not rubbing on anything between the area in your photo and the gauge. It would be unfortunate if it was to rub through and cause you to lose all the oil. Could also be a fire risk if that happened.
Good point Nige,I never thought of that
Yes - I believe its now confirmed that there is something going on inside the engine. Assuming the oil pump and pressure valve aren't defective, which is unlikely, that really only leaves the cam shaft bearing and the idler gear which aren't easy to replace. It's a very difficult situation because I can't be 100% sure. I assume this isn't over - it will eventually get worse and I'll have no choice but to deal with it somehow. Thanks for the advise on the oil line - I'm going to put it in a sleeve.
Engine out and a complete strip down to bare block to inspect all oil lines,pumps,orifices etc. It’s probably going to be more labour intensive than cost of parts. It’s always nice to install new mains,big ends etc,but not allways necessary. On a very positive note,the machine is actually still working with power and not making metal,so it’s a case of detective work with an experienced eye,and not a wild parts cannon shoot out.
It had a new oil pump and a set of main/rod bearings 500 hours ago Nicky. Unless they are on the way out again as a result of the low oil pressure the problem must be somewhere else. My vote goes with the suggestion made earlier by @HATCHEQUIP of the idler gear in the front gear train, simply because it’s so hard to get at.
Sorry Nige,I missed that post. Idler gears a way above my paygrade
Any update on this.?