Hi I hopefully somebody can help me as I'm pulling my hair out now. I have a Detroit diesel v12 71series (2stroke) that I am having oil pressure issues with. I know the pressures on there's engines are not mega high usually. The engine has been rebuilt and 'tested' by a local company a while back and just sat since and going by there sheet the pressures are all fine. All I done to the engine before it was fitted was fitting all the external parts needed. The book says 50-70 psi is normal and 28 minimum at 1800 rpm. Once it is started I only see 1 bar at 1800 and maybe 0.3 bar if I'm lucky at idle so it was shut down straight away. I have tried the obvious like a new gauge-no different. I have replaced the pressure regulator and relief valve in the sump- no different. I dropped the sump again and changed out the pump. Still exactly the same. The gauge shoots up to 5 bar on start up then drops and drops back to one bar. I'm completely puzzled. Any help would be much appreciated thanks
if the gauge shoots up to 5 bar (75psi give or take) the first thought in my mind is that the pump is making adequate flow. The drop back to 1 bar would indicate a leak somewhere, the obvious culprit is the relief valve but you say you have changed that. Is it possible there is a plug missing from an oil passage somewhere towards the end of the line in the lubrication system or does the rocker feed on Detroits have an orifice in it to reduce flow to the top end..? If so that would explain why the pressure initially shoots up then drops again.
That is possibly yes. But like I said the company that rebuilt it have supplied a run up sheet and everything was fine supposedly. I know these engines have individual o rings and fire rings under the head for dealing the bore, coolant and oil. It is possible that one could be leaking but there is no signs of anything coming out externally. I also do know the piston rings are very easily damaged when fitting into the liner. I suppose I should take the manifolds off and check the ports for any signs of oil. I did think this but didn't thing that would cause such a massive loss. If I am to try changing out all the o ring seals the manifolds will need to be removed anyway so I will have a good look
What are the pressures at Low & High Idle given by the rebuilder from the dyno test ..?
1.6 bar @ 600rpm and 4.2 @ 1800. I will have to check again to see what it had flat out. I'd imagine over 4.5 bar when it was up to 2200 rpm.
Do you own or have acceess to an air powered pump ? Plug it into an oil port and turn it on with a gauge connected and see if you caan locate a leak somewhere. Obviously not running at the time.
I can get hold of one yes. Am I right in thinking it would need to fill the whole system including the sump with air before I seen any pressure on the gauge as the air would go through the system and return as if it was going back to the sump?
Wish you were closer to my location I have something that might help, it's called a leak detector that was sold by Federal-Mogul years ago. Actually a couple ways you could make your own. This one is basically a tank that is filled with engine oil and a line off the bottom is connected to the oil galley of the engine then air pressure regulated to say 40 psi (2.8 bar) is connected to the tank. Do this with sump off and look for where the oil leaks the most. Might also be an idea to have valve covers off to see if oil is coming from valve train area. Another option would be if you have or have access to an air powered oil pump. Connect it to the oil galley and turn it on an again looks for where the major amount of oil is flowing. Almost impossible to think of all the many places oil could be leaking internally. I will admit to one mistake many years back on a 12V-71. While rebuilding the oil pump and waiting for the gasket kit to come in I installed the block off plate on the side of the pump finger tight and put the pump on the shelf. Come time to install pump installed it and shimmed the pump for proper gear back lash. Finished assembly and shipped to dealer for run-in on dyno. Came back very low oil pressure. Dropped base and found my mistake, yep never removed cove to install gasket and torque bolts. I think after that if I put a part on temp. I tried to always make it obvious that it was not tight, maybe put tag on it to say what was missing!
No, you use the air powered pump to fill oil into and "pressure" the system. Hook the line up the same place you have your gauge plumbed, and try to fill the system up. That big engine, you're probably going to need a decent sized pump. A pressurized air can isn't going to cut it.
Dang it! GregD1 you beat me to it. I need to type faster! Grogs123 what you want to do is leave base off and just pressurize the oil system to see where the oil leaks out.
Will the pressure can move enough oil to fill that big engine up?
Dam now Shimmy1 is beating me to the answer!
Cheers for the advice guys! I'm going to get the sump off again tomorrow and see if I can make something up to connect to the port on the bottom of the block where the pump sends the oil rather than through the gauge hole as its only 1/4 npt. Hopefully I will see something. Clearly
Clearly I will be getting oil returning back down but I'm hoping to see it from somewhere I shouldn't. I'm sort of thinking it could be one of the individual o rings under the head. I wouldn't see nothing externally as there is a seal all the way round the block but it could be getting back into where the camshafts sit.
Most of the Detroits had a bypass filter that caused the low pressure at idle, you might check that the restrictor is correct and that you have the correct filter element in it. The original sock filters looked like an elephant tampon....
And keep in mind that Detroits do not carry a lot of oil pressure at idle especially after being warmed up.
True but if it is only showing 1 bar at 1,800 rpm that is only equal to 14.5 psi even for a Detroit that is way low. If this is a rebuilt engine I would be expecting 50 psi at 1,800 or close to it.
Before going to a lot of work adapting to the port on the block I'd give it a quick test pushing oil into that 1/4 npt hole. If it is leaking heavy in one spot that should be good enough. I'm just glad you are not dealing with this problem on a 12V-71 in a Euclid R-35. You need to pull the engine to drop the base! Would this by chance be a genset application over here most of them run at the 1,800 rpm for 60 Cycle electrical power.
lantraxco, I'm glad I was not drinking coffee when I read that one!
I've been racking my brain on this one. I have many 12V71 rebuilds under my belt, (Wabco and Terex scrapers mostly) Never had an issue like this. Obviously you are using the same oil you have always used? Need to know how many original components were switched from the original engine. Do you have remote mounted full flow oil filters, etc. ? Something has happened since the Dyno test and installation of the rebuilt engine. Also, the oil supply to the cylinder heads shares a seal ring with the cooling system, so if that seal was leaking you would most likely have oil in the coolant.
Here is the V -71 series low oil pressure troubleshooting chart .
Yep, these are the pages burned into my brain. Plugged oil cooler would open the cooler bypass valve and still allow full oil pressure to the engine. Still quite the mystery. But that was why I asked about remote full flow filters, if the hoses were connected backwards... Or if somebody missed a caplug? Twice I have run into the missed plug issue. First time was a mixer truck with a freshly rebuilt Sundstrand pump, sucked the plug all the way into the charge pump inlet. the second was an Allison 643 that had a plug in the cooler return/lube line. Neither were my oops, but I had to diagnose and fix them.
I am very familiar with what those sock filters looked like, but what I really want to know is, how does lanway know what an elephant tampon looks like??!! Or, maybe I don't want to know....
Ran away and joined the circus as a lad, because my parents were so dumb... after a short stint with the circus I decided to go back home, not sure what happened but the folks sure seemed a lot smarter when I got back.
Hi everyone: we have 2 Detroit 12V71TE in our boat. We wanted to be nice and replace the oil filter and now we are not getting oil pressure on one engine. (We only replaced it on one engine) we have no way to go under the engine to open the oil pan. We filled the oil filter full with oil but to no avail. So, replacing the oil filter caused this and don’t know where to start. Would appreciate any help, thank you.
Interesting. Remove the new filter and take a look-see. Not much could have gone wrong. Did you leave the plastic wrapper on the filter?
Thanks for answering and funny that you asked about the plastic wrapper , there’s definitely no plastic wrapper on the filter.
How are you determining that there is no oil pressure, actual mechanical gauge or electric. If electric are you sure that it is working and that a wire didn't come loose somewhere.
After starting, it would idle for 2 minutes and then the buzzer would go on and read very low pressure on the gauge
The best place to start of course is to verify the engine oil level (I know but it happens). Then plumb in a mechanical gauge so you are absolutely sure there is a problem. Those electro mechanical devices can fail like everything else.
Did the oiler or head wiper forget to fill the crankcase? What was the thought process or reason to randomly change a filter? Without performing an oil change? There has to be more to this story. We need all the drama to accurately answer your question. How much crankcase oil is in the bilge? What’s the name of your boat? Does it have a pirate flag? I don’t have any work lined up this weekend. Give me your credit card number and what pier and I’ll pack up my game and fix it for you.
Remote filter set up? Did a ball valve get closed?
Double?
Bump the RPM up a couple hundred and see what your oil pressure is. minimum Idle pressure is 5 PSI on this engine. Bob
Yes people who are used to "other engines" can get scared with the readings on a Detroit at idle. Seem to recall having some problems with off0highway Mack's with 16V-71's setting off low pressure warning systems at idle. Think the Mack engineers were thinking they should have the pressure of a Mack 6 cylinder at idle and put in the wrong pressure sensors!
Good point, kshansen. It’s not unusual to have oil pressure alarms buzzing occasionally on a hot idling Detroit. Especially with the reduction gear engaged.
One has to remember it's just a Detroit, nothing to get excited about.
If replacing the oil filter caused the problem, look into the oil filter. Is it the right filter, was it installed correctly, was trash introduced into the system, are gaskets in place? DON'T start changing other things until every possibility with the oil filter has been carefully examined. Yes, it is possible something totally unrelated to the oil filter broke at the same time as the filter was unchanged. But that is very highly unlikely. Unless you were the one who changed the filter, there is a high likelihood you are not getting the whole story.
What brand and rating is the oil? Should be straight grade 40 wt.
I know nothing about Detroit’s,but during the 90’s I bought some scrapers for a quick job,then sold them.I recall an important thing or 2 about them……they ran on straight 40w oil and would all work fine until they needed servicing.They would run about 40 bar then after a month would suddenly drop to 10 bar.They would immediately get oil filters and new oil and work another 200 hours or so before doing it again.This was the case with all the scrapers.My fitter was never concerned. The correct oil,oil filters and frequent changes was vital to these engines.Air filters were also important to keep clean. They were good engines,but took no abuse unlike the Cat engines
While most on here won't or refuse to believe this, I knew and worked on Detroit's that a guy owned THAT never Removed the DRAIN plug till major work was done, Filters only. He only added-Most all ran a minimum of 500,000 He two 8V92 silvers that ran close to 800,000 before needing cams. Fact.
I'd believe that. Speculating that it was probably because the amount of oil that the engines leaked/burned led to him effectively changing the oil every X miles/hours by having to add fresh oil regularly to keep the level up to the mark.
I'll bet that oil was a pleasure to wash off if it got on your hand.
Ahhhh....the memories. I feel like I'm 25 and working for Terex again! Thanks guys
India Ink! Now you know why I hate V series detroits.
The other issue that no one has addressed is fuel dilution. A V12 has a whole lot of jumper lines that could develop some seepage or a leak.
That's true with four connections for each cylinder you have 48 possible leaks. Plus if someone did not know what they were doing when installing a fuel pump and put a pipe plug in the threaded holes between the oil and fuel seals that could be another source of dilution!
We would eliminate the Oil Side Murphy switches on Driptroit powered Trucks, would bump low oil pres and Die at inopportune moments, Idle would or could be as low as 2-3psi
The guy changed a filter noticed low psi, apparently had no issue before-now we are into making oil?
If swapped a bypass for a full flow could do it as to low pressure, marine used to be all upgraded spin ons.
Another post and run.
I'm gonna bet he prefilled his filter with 15-40 oil and you know what that will do . Bob
I find it real hard to believe you had DD motors running 560 PSI oil pressure. Bob
I agree, maybe he's not sure about the conversion of BAR to PSI. I'm guessing he meant 40 PSI and then it would have dropped to 10 PSI, no engines I know of could use 40 BAR of oil pressure, that would over whelm the oil control ring from the massive spraying and windage in the crankcase, and likely erode the bearings.
Yes,I meant PSI . Sorry about that.It was a long time ago and, as I mentioned,I’m no fitter.I’m just the chap that owns them and moves muck with them. I employ better men than I to advise me how to spend my money on my machines.This has worked very well for me over the last 30 years allthough mistakes have occurred My ownership of Terex scrapers was deliberately brief and I ran some for just one particular job.They we’re impressive little scrapers and considerably lighter than the equivalent 627’s I’ve worked with over the years and would work in soft material far easier than the 627’s.
Obviously an error on my part.40psi sounds more like it. Again,my apologies sir.
Guys. Sorry for the late update. I don’t always get a chance to visit the boat. After some searching, there was this tip about diesel seeping in to the oil through the injectors. When I had a chance, I took the dipstick out and would you believe it, it smelled 100% like diesel!!!! So this is what is going on. It’s totally unrelated to changing the oil filter. That’s what we were thinking because it was fine before we did that job, but like another poster mentioned, some other stuff could happen and misguide you. I am hoping that it’s the injectors only. Not sure yet how to easily analyze this, and I’m hoping it’s just on one side of the engine because is unbelievable how hard the access is in a boat. Any tips would be appreciated to er this job going. I don’t have a workshop manhal on this engine. Thanks guys!!
John, this is EXACTLY the problem. I smelled diesel on the oil dip stick! Any tips would be appreciated on how to go about fixing this! Thank you!
Pull the rocker covers, if the fuel was that diluted it probably has washed the cylinder heads fairly clean of black oil. Dump engine oil add new oil. Start and idle watch all fuel crossover/jumper lines for leaks right at there base fittings go through and physically grab each one and see if any are loose or have more movement than others. Good catch-John C.
Thank you very much! I will try that as soon as I can
You can look at the connections to the injectors. The leaking ones will be completely clean while the properly torqued ones will have oil clinging to them. If you find leaking ones, just replace them. People over torque them and crack the flare on the tube. Nothing you can do with them at that point.
thank you for this tip. Does anyone know of a service manual and parts manual of this engine to download somewhere? I have no manuals or any reference and these engines are so old.where would one get parts? Thanks
Fleabay, will only be generic 71 series DD Engine manuals, parts manuals are relegated to dealers for the most part as are dependent by S/N in most cases and variables would fill catalog sized volumes that could fill a kitchen counter. I traded my own manuals to another here on the forum as could use them. As to buying parts, primarily go online and Google 'Detroit Diesel 71 series parts suppliers'. Locally check with HD truck or boat garage sites as to who they use.
Like Dmiller says, any good boat engine shop that services old fishing or transport vessels should be familiar with Detroit 2cycle. All those islands around Greece, there should be some detroits still shuttling around.
https://mpd-greece.business.site/
Guys!!! Here’s the update! I found the issue of fuel dilution: I uploaded a video on YouTube. It was pissing diesel from fuel line One. It was very loose. Now I tightened it and no more pissing diesel. Now I’m sucking out the oil to replace it. Thanks everyone! Here’s the video
Well at least for now that engine looks nice and clean inside!