Please help me diagnose the root cause of my CAT D8L transmission overheating issue: Equipment Specs: Caterpillar D8L SN:53Y02410 Backstory: With all the rain we had in OK, most of my lower most productive farmland was flooded and debris covered. In a last ditch effort to "save" the ranch I decided to splurge and get the best condition D8 size dozer I could afford and give it one last go. I did a tremendous amount of research and determined the best option for us would be a low hour CAT D8L (all mechanical, great reputation etc). I found a machine about 8 hours from me with about 3k hours on a certified engine, torque converter and transmission (about 12,400 frame hours). After speaking with the owner and his mechanic I felt comfortable that it was a good machine and bought it. I literally cried as I drove the dozer off the truck and watched the transmission temperature creep up and after walking the dozer about 1/4 mile it was a hair from throwing on the powershift transmission light. I parked the dozer and so far have: 1. Power washed out the radiator external (removed a lot of debris toward the base) a. Tested the radiator fluid (was great), but I flushed it and used 3 gallons of the CAT flushing fluid. b. Tested the machine and engine stays pretty cool, but transmission temp creeps up to an unsafe level in about 1/2 hour with 85 degree ambient temperature 2. Changed transmission fluid all filters and screens (also had tested) a. Filters and screens did not have any debris b. oil test: Silicon 18.01 PPM, Tin 0 ppm, Silver 0 PPM, Aluminum 2.06 PPM, Chromium 0.33 PPM, Lead 88.9 PPM, Copper 178.22 PPM, Nickel 0.111 PPM, Iron 252.51 PPM (Maybe pump issue???) 3. Cleaned all break linkages and parked on hill (seems to roll ok in neutral) (forward and reverse) 4. Things that I have bought a. All books (parts manual, maintenance, operator) 5. I spoke with former owner and mechanic - I suspect they knew something was up, but obviously swore that it worked great when it left (but they used it very little) 6. I bought a set of pressure gauges, but have yet to connect up and pressure test it 7. Dozer has a ton of power and transmission shifts in all gears and drives true, clutches and breaks work as per specifications I really don't have that much time or money, I tried to have CAT come out, but its not close to the dealer and they are booked up with all the big guys .... I work the ranch mostly on weekends with my 6 and 8 year old boys. I do have access to a rebuilt transmission pump and possibly the scavenger pump (I don't know where this is located though?). How hard is it to change out the pump? can I do it myself? The book is a bit lacking in details, is there anything I need to look out for? Do the pumps need to be primed?
Do you still have the old transmission filters.? If so cut them open and look in the bottom of the pleats for debris. Lots of how to videos on YouTube. Before laying tools on it I suggest that it would be a good idea to get a full set of pressure readings from the power train. Converter Inlet Converter Outlet (stalled in 3rd speed) P1, P2. Trans lube pressure. If you’re not sure about how to perform any of the tests don’t hesitate to shout out. Your oil analysis results don’t look very good. Starting from too much silicon (dirt) and only getting worse with the iron, copper, & lead. I’m sure that you have no idea how many operating hours the oil that you drained had, and that doesn’t help much. I dunno about anyone else but I certainly wouldn’t start swapping parts without some hard test data to justify why I was doing it.
Thanks for the quick reply Nige!!! I have a pressure test kit at the ranch, I haven't opened it yet, but will do on Friday after work. I do have the book that generally indicates the test points, however, if you have a better procedure or one that makes more sense in my case I would love to have it. It may be a stretch, but in your opinion, what is best case worst case for my situation (or is it just to hard to tell with the data points I have so far)?
Just so we know if you have the book that shows the test points. Look at the attached file and see if this is wat you book is showing:
Agree with Nige*check your pressures also might pull the trans cooler the water passages get stopped up you can check it wit a temp gun and see if it is removing the heat
This diagram is indeed what the book outlines for pressure testing - thanks
I do have a heat gun and when the transmission temperature was reading about 190 deg c on the gauge (very hot in my opinion), I noticed a 40 deg F temperature drop across the oil cooler
40 degrees temperature drop across the oil side of the power train cooler would appear to be in the ball park. You've already got a number of people interested. Stick with the plan, work through testing everything logically, and you WILL get to the bottom of what ails the old girl. Brings back memories. I had a D8L S/N 53Y02422 from brand-new on a job I was working back in early 1984. Time flies.......
There is a 53Y here in the UK literaly working today on the A9 Scotland
Has the temp been verified as hot? …..or did I miss that part?
No you didn’t. It might be a good first step to shoot the TC out temperature with an infra-red just to confirm that the EMS temp sender is working correctly.
You say 190 deg c but I think you mean 190 deg f. 190 is not hot for a transmission. It should run warmer than the engine when it’s working. What is the temp when you say it’s at an unsafe level?
Hell no it's not high. I missed that. Normally the alarm for high TC Out temp comes on about 120 C (or more) which is about 245 F minimum if my maths is correct.
190 C would be 374 F. I dont think the guage on ours even goes that high ?. Ours was tripping the warning light about every hour at about 245 F. through testing with a heat gun I determined that it was the cooler. After eyeballing it I decided it would be easier to clean the cooler on the machine without disturbing all of the hoses connected to it. First thing I did was dig a 3 ft wide trench 4 ft deep the full length of the cat and ramp one end of it up real nice. Then walked the cat right dead center over it so the ramp was comming out under the rippers, Then I swung the front belly pan out of the way (hopefully yours is on hinges), Drained the water out and once it was empty I also removed the plug right next to the drain valve ( this will help wash out the gunk when you flush it later), Then removed the bolts from the cooler mounting bracket and let the drivers side (left side from the operators seat) sag down as far as I could, remove the one water line from the left side bonnet and then the left side bonnet its self from the cooler. Now the nasty part, Take an 1/8" copper rod and push it through every tube. when you're done have someone puor buckets of water in the radiator or use a garden hose and flush out the gunk you pushed through with the rod, Then put in the plug ( finger tight ) and close the drain valve and start pouring in the water again and it should start coming out the tube. With the water pouring out the tube take your blow nozzel and force the water back through the tubes. When you've done this thoroughly then open the plug and valve and flush it again. When you're happy with it put it back together. If it was plugged as bad as our the difference will be astronomical
Most folks don't bother to replace the power train cooler (or the pump for that matter) when a transmission is changed. Fasle economy, both should be changed, especially if the transmission fails in a catastrophic fashion. TBH I would have just replaced that cooler in the photo above, I wouldn't have even bothered trying to clean it. But whatever works is always good so long as it gets the desired results.
Never saw a reply to this. I know it's a long shot but if by some chance you still do have the filters cutting them open could yield some important clues.
I would not even think of reusing an oil cooler on any system that had failure and would only consider reusing if I had a good history of samples to reference. At least with pumps you can open up and inspect and measure things like end clearance and back lash on gears assuming there are spec's to go by.
Hey guys has anyone had good success getting getting accurate readings on these oil coolers. I've had few non contact guns and don't usually get good results. The best results I have are with radiators and big oil coolers air to oil where there big temperature differentials and inlets and outlets are opposite ends. Hydraulics and power trans not good results I got a termo camera hoping for better results.
My thoughts on this 8l. It's heating up really fast should make finding it easier. First install new temp gauge weather one piece or sender and gauge. When changing gauge drain just torque converter if you get a gallon or two most likely scavenge system is working. If it fills 5gallon bucket check for screen in scavenge line.
If it feels strong. most likely in that short amount of time oil cooler or torque converter over full.
Thing is Ken, that compared to the cost of the replacement/repaired transmission the cost of a replacement cooler and a pump is peanuts.
I just read through all the responses and Thanks! You all are great! I was able to get some pressures on Friday, it was pouring rain AND I noticed that the gauge set I have isn’t really designed for 0-500 psi, but more of 250 - 3000 PSI test kit. I have ordered a gauge set that is appropriate and these are the readings I could take. 1. I off right side filter tap (lubrication) at idle not registering, max rpm maybe 10psi. 2. Left side (transmission) filter tap ~400psi 3. Outlet from torque converter about 75psi at high idle not in gear, in 3 gear stall brake on ~ 60-65PSI 4. Torque divider input A 95 psi Again I will get better resolution gauges and try again later this week, but do you all have any preliminary thoughts based on this data set? Any other tests I should do that aren’t in the manual?
And one other thing, when changing the screen in the torque converter it lost at most half a gallon of fluid - is that a good / bad sign?
I have uploaded the gauges as hot as I let it get after about 30 minutes of medium - hard pushing at 85 deg F ambient conditions
I miss Scotland! I lived / worked out of Aberdeen for 4 years! Had many a good night on Crown Street!
I don’t have the old filters, but did cut them and squeezed in vice and did not notice any metal flakes? I did have oil tested and listed it above
Lots of good info above. Responses in no particular order: - 1. For transmission lube pressure you really need a 0-25psi gauge. Idling speed lube pressure is 4/5 of 9/10 of ***k all. 10psi @ HI appears to be on the low side compared to spec of 26psi but could just be down to the gauge you are using. 2. Pump pressure is a bit low at 400, I would have liked 425-450. 3. You need to get pressures for the transmission P1 (speed) & P2 (direction) clutches. 4. Converter inlet pressure acceptable (spec is 100psi max), outlet pressure down a bit, should be around 80psi. It may require some adjustment but again - gauge accuracy.? I would do anything until I'd confirmed the pressure reading. 5. 1/2 gallon of oil from the converter housing is probably about normal. Did you find any particles in the screen.? 6. TC Out temps. Around 100C I would class as "Low". Try running it a bit longer but don't let the TC Out temp go above 115C (240F) for now. See how long it takes to get up there. If the temp gets that high slip the transmission into neutral and leave the engine at High Idle RPM. See how long it takes for the temp to go down to 100C. 7. If you cut the old filters, looked for metal in the pleats & didn't find any that is a good sign. Here's a question for you. Are you basing your idea of "high" TC Out temperature on the fact that the needle on the gauge is not the same angle relative to the needle on the engine coolant temp gauge directly above it and the hydraulic system temperature on the right..? Because that's a common misconception. "Normal" temperatures for the systems will result in the needle on the TC temp gauge swinging further over to the right than the ones for engine & hydraulics.
Thanks for the feedback Nige, I uploaded some pics of the gauges when it was hot as above, if I let it get any hotter the power shift temperature light will flicker. Next time I’m out there I will time exactly how long it takes to get hot and at high idle how long it takes to cool down. Hopefully I’ll get some good digital gauges and will be able to test further later this week. A question on the test ports, some of mine seem to be blanked off and do not have the port on them. Do they come from factory like this? Should I get a pack of test ports from CAT?
Any point that is shown in the photos of your Service Manual as a pressure testing location should have a self-sealing coupling installed in it like the ones you have already tested. Part Numbers as follows: - 6V-3965 Nipple (each one requires a 3J-1907 Seal) - $21 ea. 6V-0582 Dust Cap (black) - $4 ea. Don't just get the light flickering, get it ON solid for say 30-60 seconds then flip 'er into neutral as described above. Thinking more about it I'm wondering out loud if there might be some sort of fault in the sender/sensor for the warning light because I can't understand why it comes on at such a low (relatively speaking) temperature. To me it shouldn't come on until about 120C.
Thanks Nige - I’ll do as you recommended in regards to getting her hot Monday. I wish I could upload my iPhone Live Photo that shows the light flickering just as the transmission temperature exceeds 100 deg C.
Don't get me wrong. I believe you, it's just I'm having problems convincing myself why the light should come on at such a relatively low temperature. EDIT: See the attachment ( Check the EMS system first - Point 2 ) - I was right, the light should come on at 127-133C (260-270F) You may have to replace the TC Out temperature sender (6N-5926) and/or the TC out temp gauge (8N-2977) Next time you run it, give it beans - you won't hurt it...!
If you want to check your TC Out temp sender, try removing it, place it in some hot water and measure the resistance between the terminal on top and the screw thread on the body (ground). The test may also work with the sender installed and resistance measured between the screwed terminal on top and machine frame ground. @ 130DegF resistance should be between 5800 & 7250 ohms. @ 240DegF resistance should be between 525 & 585 ohms.
Nige, Thanks again! I was out at the ranch yesterday and worked on the dozer a bit, I checked all the electrical connections and cleaned all parts. I haven't moved the dozer in a couple weeks and this time, when I went to engage the right brake nothing happened - The left engaged, but further back than usual. I played around with the linkages and finally after raising the RPM to near max the right and left brake were engaging, but really not as snappy as before. I tested to see if the brakes were free on a small hill and they were free in forward and reverse. It did take about 35 minutes for it to heat up and the light starts to flicker a hair over 100 deg C on the gauge. I did have the parking break engaged for testing - could that be sticking slightly? I have cleaned and checked all linkage components and they seem very free? I kept working it until it read about 105 deg C and used my laser temp gun to read the transmission filters - they read about 213 deg F. From this temperature it took about 5.5 minutes for the temperature light (blinking) to turn off at high idle in neutral. New developments 1. Brakes (lazy) not engaging? 2. temperature gauge was a bit jumpy as per attached pic? 3. The Coolant flow light came on (I double checked the radiator level and the cap was tight - no apparent leaks in system) I'm getting a new gauge today with 0-100PSI capability and getting the testing nipples and a new temperature gauge and sensor, also attached a video of her heating up. Side question - the reservoir / tank under the transmission fill - what is this for? I don't see it in the book anywhere? I have attached a pic of that as well. rgds, Eric S
If it takes 5.5 mins for the TC temp light to stop flashing @ HI in neutral then I would say you have a cooler problem. When you throw the trans into neutral the temp should drop like a stone - 60 secs max I would’ve thought. Do the same test you did before and get the light on, then try shooting the temps on the oil in and oil out lines of the transmission cooler while the temperature is falling. Post your results. The tank by the trans filler is for the pivot shaft lube. Do you have an operation manual for this tractor.?
Yes no real experience with the D8 but from all the other machines I worked on if say you were doing a stall speed test and the trans oil temp get up near the "red line" as soon as you click it into neutral the temp gauge will start dropping like the second hand on a clock. Only two common problems I can think of that would not let this happen. First and most likely is a problem in the cooler causing a restriction of flow either of the oil or what ever is cooling the oil, air or water. Next would be a problem in the converter system causing a flooding of the converter housing. This could be a plugged drain line or a major leak in the converter that plain overwhelms the drain system.
Did you see his earlier post when he reported about half a gallon coming out of the converter housing when he pulled the scavenge line to clean the screen.?
I don't suggest this likely but unless the electrical system is playing up.The water flow light coming on, the engine temp gauge all over the place and high transmission temperature indicates to me that you may have a faulty water pump 1/ if the machine has been running without coolant conditioner the water pump impeller and the adapter plate will corrode away (Low Flow) 2/ the impeller is a taper fit on to the water pump shaft and may have come loose 3/Cat had a bad bunch of impellers years ago on all 3400 engines. They tried a plastic type impeller wheel bonded to a cast hub the bonding breaks down and the impeller can slip but not all the time. The only way to check for these conditions is to remove the water pump cover and adapter plate and physically check for corrosion and slipping impellers I don't suggest this lightly because they are a real pain to get access to
Good point Mark. The symptoms fit. In you first line did you mean to say “likely” or “lightly”.? The latter kind of makes more sense due to the ball ache of actually getting access to the working parts of the water pump. Up until a couple of posts ago all we were dealing with was high TC Out temp, then all of a sardine up pops a low coolant flow warning and temp gauges fluctuating which sends the diagnostic trail off in a totally different direction. I agree with you that the possibility of a pump issue should be eliminated before moving further.
Looks like "auto correct" is working overtime today.
That was my thought too. I just wanted clarification that what I think Mark was saying is what he actually meant.
Thanks for the suggestions Mark & Nige, I do have a brand new water pump for the old girl. I bought it at an auction with some other spare parts before another D8L went up for sale (I ended up not getting that one). I'll look in the book, but I take it that I'll have to drain the radiator to change out the pump? I also bought a new sender unit for the torque converter as well as gauge and built three pressure test jigs (0-60psi), (1-160psi), (0-600psi) and got more testing nipples. I'll keep you all updated !!
Seeing as you have already purchased a replacement TC temp sender unit it might pay you to install it first and do a few tests to see if it makes any difference to the TC Out temp readings on the gauge before going after the water pump. It won't cost you anything. Before removing the water pump I would drain the coolant first and then flush the system out with plenty of clean water until the drain is running really clean. Refill the system with water until you are 100% sure that everything is leak-free, then drain and refill fill with 50/50 premix (red) ELC as coolant would be my choice. Anything that meets Cat EC-1 specification would work.
Heard a mechanic talk about the elc coolant today and using it in older machines. Said some with a lot of corrosion it would cause them to leak because the elc would dissolve the corrosion and allow it to leak in weak spots. Is this true?
So from all the pictures of gauges you’ve shown I haven’t seen one where the trans is overheating. If the lights coming on and flickering before the gauge hits 250 that is a problem with the temp switch for the trans light which is not the same as the gauge sender. The early d8n crawlers would run over 230 all the time due to an undersized cooler . Cat factory rep said if the light isn’t on it isn’t hot. I think you have more of an electrical problem. Have a look at 7n9560 converter temp swtch
If R&I water pump, also remove trans cooler and clean the tubes. Hanging down low, all of the fine crap settles in the tubes.
A good flush job will/should reveal those weak spots without the ELC. If it does leak, that's not to blame the ELC, there was an existing issue to begin with that should be repaired. The last two truck engines I inframed had junk radiators in addition to the worn out engine, rotting tubes and fins.
Good point, the high temp light and the gauge are fed from separate senders. 7N-9560 replaced by 203-3221, price about $65.
Hello Stabber. I'm not in the league of these chaps that are busy solving your problem with your D8,but I'm starting to think that there isn't much wrong with the beast. Your temp gauges aren't giving me stress.Infact,they look cool to me. Before you pull the water pump,I'd be buggering about with that water flow sensor.They can lead a man a merry dance if,like me,he's no fitter. As for the jiggery pokery she gave you the other day after it had been stood a few weeks,remember that she is a big,old girl with a hard life behind her. Treat it like a woman........Start it up,don't touch it at all,climb off,and leave it idling for 15 minute at least. Go and have a nice cup of tea or something before even thinking of returning to operate it. You'll probably find it in a whole different frame of mind,and will find it performs far better. As for the cooler thing,It costs nowt but time.You must do this task.It will give you an indication of the innards of your cooling system.A good clean up,flush out,and the correct bit of coolant additive and I think you are good to go. You've done all the heart stopping jobs already with the filters and torque. I feel you're on the home run,and perhaps your limited experience with the beast has got you on your nerves and abit over cautious. Nowt wrong with that though.
Thank you all very much for your help so far - I wanted to give you all an update. This weekend I didn't have much time but I was able to test the transmission pressures with the new better resolution gauges. All tests were inline, unfortunately I left my sheet of paper at the ranch, but I will take a picture of the results and post them. After the tests I ran the dozer with the new temperature gauge and sender (didn't have a chance to run to cat and get the converter temp switch that controls the light). The new gauge / sending unit did not jump around and seemed to be working much better. It was about 98 deg F outside (hot hot) and I ran it for 25 minutes before the transmission temperature read 225 deg C and the light started flickering. It took 70 seconds for the light to turn off at high idle neutral and about 4.5 minutes for it to cool down to 100 deg C (again high idle neutral). The coolant flow light flickered throughout the operation (coolant full and cap tight). I waited for the beast to cool down and took off the water pump (what a miserable job). The old pump didn't look to be in bad shape and the gear / impeller seemed to be very well connected. I didn't have all the right seals and was completely beat, so I cleaned up everything, but did not install the new pump that I had in inventory. This week over lunch I will run to cat and get the seals as well as the converter temperature switch (7N9560). One other thing, there appears to be a check valve (relief valve) on the transmission oil cooler (read in book). Is this something that could be closed shut, or only partially opened? I love this old girl, but she has taken a couple years off my life ……
98F ambient ain't hot - I would guess our max here is somewhere 90+ for most of the year (tropical climate). We're currently sitting at 95F @ 2pm local time. Don't misunderstand me, ambient temperatures like that put a premium on cooling system performance so you have to make sure everything's top notch, but a system in good order should be able to deal with it. The thing is that the engine coolant temperature isn't skyrocketing therefore it would appear as though the coolant side of the system isn't the problem. Nice to hear that the TC Out gauge fluctuation has disappeared with the installation of a new temp gauge and sender. Check one box …… TC high temp flickering @ 225F TC temp, is too low. It should not come on until at least 127-133C (260-270F), so the obvious next step is a replacement sender unit (note that 7N9560 is replaced by 203-3221) 4.5 minutes for the TC temp to drop from 225F (I assume the C in your post above is F) to 100C/212F is waaaaaay too long IMHO. The TC temp should fall like a stone from whatever it is when you select neutral to a temperature say 10-15F above whatever the coolant temperature is within 60 seconds or preferably less with the engine @ HI. From that point it will fall more slowly as the oil & coolant temperatures get closer together. You're already into the water pump so if that doesn't solve the problem then the issue would appear to be somewhere in the oil side of the powertrain circuit. I guess at that point it could be worth a look in the cooler core but I'd be interested to hear what others think. Not sure what you are referring to regarding a check/bypass valve in the powertrain oil cooler circuit. How about taking a photo of what's in your book and post up what you are looking at.? It also might pay to quote the Cat Publication Number of the book you are using.
Nige, Remove Transmission and Torque Converter Oil Cooler 1375-11 page 30 Remove adapter (2) and disconnect line (3) from the torque converter pressure relief valve at the oil cooler. Location: oil cooler bonnet (lower side beneath oil cooler) to water pump inlet elbow. Form # SENR2334 3408 Vehicular Engine for D8L Tractor / for use in service manual D8L Tractor SENR2329
Found it in the D&A. Weirdly there is no trace of it either on the powertrain oil lines or the powertrain cooler & mounting....and it doesn't appear in the SysOp for the powertrain oil system either. I guess the next question is does the OP's tractor actually have that valve installed..?
Thanks Stan, I just took a photo of the book page as in the image below. Do you know the PN for the relief valve? I can't find it in my parts manual.
That's why in my post above I was asking you to check is that valve actually installed on your machine...… 'cos I can't find it in the Parts Manual either,
Part Manual: 7N7023 LINES GP-WATER S/N 53Y1 thru 3101-Up page 46B-47 and 47.01 SEBP 1356 Adapter #7N6604 round-ish bolted to rectangular block with 2 plugs. I cannot fine a breakdown of the relief valve in the parts manual or specifications in the service manual either. Edit: Looks like the service manual is referencing the torque converter 'outlet relief valve' as torque converter pressure relief valve (line #3) @ the oil cooler. No valve exist @ the oil cooler, just a 4-bolt flange, o-ring and bolts. Per my memory.
With it taking that long to cool I would pull the cooler and check it out I use a piece of brazing rod with out the flux to rod out each port. flush out the oil side too if you get anything out of it I would replace the cooler
what the book is telling you about the location of the torque relief is wrong. Its on the back of the converter housing with the line going to the cooler coming out of it and it is a rectangle block with 2 sending units in it, easy to get off only 3, 3/8" bolt hold it on the converter and its all O-ring seals. You don't have to mess with it to clean/ change the tranny cooler. I say this from experience with our 8L that is also a 53Y. The picture the book is showing with arrow #2 pointing at it is the drain valve for the cooling system that is part of the cooler
I'm planning on going out tomorrow after work and will take a picture and see if I can find it. Stupidly I didn't when I was working on it …
You mean this one..? #15 & #19 are the two TC temp senders, one for the gauge, the other for the high TC temp warning light.
Turbo, Do you have any experience with those valves sticking shut? Do you know the PN for the valve body? I'll climb under her tomorrow and take a picture, but when I changed the sending unit, it looked like it was attached to that? Will I get a ton of oil out of the system if I take out the relief valve without draining the system? Can I run it without the relief valve to test it (put in a plug?).
hi
That looks 100% like what I have, any good way to check the relief valve?
use the test port in the picture
60-65psi < low, low Spec 80psi +/- 5psi, brake applied, 3rd gear forward, torque converter stall Engine High Idle, Spec 2020-2120
I don't, The 8L we have now is the only one i've been around and I don't know the part # but I'll bet somebody else does. It is easy to take apart and inspect the piston tho. You shouldn't loose but about a cup or maybe a quart of oil. No, you can't run it without, It must have a way to relieve the pressure and circulate the oil. You may have some other components getting tired/ weak but for your heating problem my money is on a plugged up cooler. Ours was tripping the warning light regularly and after I cleaned the cooler I can't get it over 190' F no matter how hard I try
This issue came up earlier Stan, but there was doubt regarding the accuracy of the 250-3000psi range test kit gauges that the OP was using. In post #49 above he alludes to having repeated the tests using more suitable gauges but forgot the piece of paper with the results. I suspect that you're right and TC out pressure will come out low, but I wouldn't like to say that for certain until he posts the results. Even if TC Out pressure is low that still doesn't explain to me why it takes almost 5 minutes for the TC Out temp to fall @ HI in neutral after the high temp light comes on. That indicates problems in the cooling circuit somewhere.
Pull the piston out of the valve and make sure it is free if it is bypassing it would be stuck open not shut
I see the cooler is still on the tractor. It has to come off and be cleaned or replaced I think. Removing it will be easy compared to the hateful water pump job. I feeling you are pissing uphill into the wind until you get the cooler off
This weekend I will remove the cooler, I suppose there isn't any way around draining all the oil?
Nope, sorry. Just another thought from left field..... Reinforcing what Nicky said above, get the cooler off and clean or replace it. After that wouldn't it be something if the TC Out pressure changed because of the differing resistance to oil flow through a (now) clean cooler..?
Nige, That was my thought exactly … I just need to motivate myself to get under the machine in 90+ deg weather … I guess at least i'll be out of the sun
OK 90+ with humidity, not fun. You won't have much oil to drain just working on the cooler. After you get the cooler off. Drain the oil and tape up the openings. Use 1/8" diameter brass rod, rod out the tubes and pressure washer or use solvent gun. I am located in S.Cal and our D8Ls, D9s are all re-powered with electronic emissions engines (if they're not used for AG). Normal emissions engine temp 190-210F and normal TC-Trans temps 220-230F. Working ambient temps 120F+ are normal. Flicking Trans light @ 240F, just tells the operator to ease off a bit, like use 2nd instead of 3rd forward-reverse. Accumulated dirt stacked up in the crankcase guards will also cause higher operating temps because of the insulating dirt. Reference: Torque Converter Outlet Relief Valve: 3T3505 VALVE GP-RELIEF part of 7G5126 Lines-Power Train Oil page 137
Update - I removed the oil cooler and took it to a shop in Oklahoma City that cleans and services the coolers regularly. They said mine wasn't that dirty :-(, so I will put it all back together this weekend. Just a quick thought I had, on the left side of the cooler, there is the small outlet hose that feeds back to the engine (Left side sitting in the seat). Is there any relief valve on the water side that could be faulty or restriction (thermostat) that regulates how much coolant flow comes into / across the cooler? This was a cold(er) weather machine coming from Wisconsin ….
Once you get everything back together snap a photo of the hose you’re talking about and post it up.
It's a shame you didn't find the cooler dirty Stabber as it would of been an explanation. At least you've eliminated it though,and it may have had just a bit of trash in it that's now out. Were any of the tubes blanked off at all?
Tube blockage or partial restriction, e.g. slowed fluid flow , 10%, 25%? Unknown! Hose Assembly: 6N8785 approx 48" length, oil cooler torque converter bonnet (left side sitting in seat) to engine. No valves or pressure regulators. Remove the line and fittings (elbows) and check if there is any type of internal restrictions. Radiator: Conventional or Folded Core? Auxiliary Hydraulic Oil Cooler? Has or has not? Torque Converter flooding? Lock brakes, stall at high idle 3rd gear forward. Use per-positioned 3 gallon capacity bucket. Shut off engine, and quickly remove the screen-cover and drain oil into the bucket. Over 3 gallons! Remove and check scavenger pump for damage-wear, if pump is okay. Remove and repair torque converter assembly!
Weekend update: I put back on the new (cleaned) oil cooler, no blanked lines as well as putting in the new water pump and all new seals etc. Man what a job to do with your 6 year old boy! I filled up the radiator with some flush cleaner, and while I was filling it noticed that my seal on the water end of the cooler was spraying out water. I crawled back under it and retorqued the bolts, but water continued to stream out. I figured I would finish filling it with the flush solution, but as I filled it the leak died down then stopped!!??!! I started the beast and ran it about 30 minutes and didn't have any leaks at all???!!?? Now I'm paranoid, should I remove the cooler again and check the gasket? I cleaned all surfaces very well and put gasket sealer on both sides before reassembly …. but I don't want this problem to surface again after I put back on the belly pan …. I ran out of daylight before I could load test it and see if it still heats up …… More to come next week
Normally those gaskets go on without sealer. Did your sealer have proper cure time?
I put on cooler Saturday about noon and filled it Sunday about 6pm, and the sealer stated it could be used immediately 500 deg F jargon … oh man now second guessing putting sealant on gasket :-(
Not saying it's the case for you but I have seen gasket sealant act as a lubricant and let a gasket slip out of place while tightening the bolts. Unless I felt there was a good reason to need sealer most gaskets were put on dry. And when I did use a sealer put it on very thin. I would not feel too good about a gasketed joint that was leaking with just the weight of cold water against it. Especially one that was described as "spraying out". Sorry!
Those mating surfaces can often be fretted and pitted in old tractors. I've had same problems. They often cure themselves when they warm up
Weekend Update: 1. The beast is back running and the following things have been fixed a. The coolant flow sensor was changed and light no longer blinks. b. Oil cooler changed all leaks sorted - coolant system flushed 3 times with distilled water and new premium coolant filled (Now has new water pump and regulators) c. Both powertrain temperature sending units changed out I worked it about 40 minutes and it did start heating up, but I didn't work it until the light would come on, but just a hair before based on the new temp. gauge. It still takes about 4 minutes at high idle to get the temp to drop to 100 deg C. Ambient temp was about 85 deg F. I did take some pressure measurements with it hot and the results were off from the previous round when it was just warmed up. 1. Off the torque converter in third gear (stall) brake on the pressure read 71 psi, should read 80 +/- 5 psi. 2. Off the transmission lube port, i read 0 at idle and 8 psi at max rpm. 3. Off the left hand transmission filter max rpm read 474 PSI. I'm going out to the ranch to finish the pressure tests this afternoon - I have spacers for the torque converter relief valve, should I add one as per the book? Do I need to take off the entire relief valve from the TC, or can I pull just the valve body? thanks for all the input so far!!!!!
Weekend Update II: So I added a a couple shims to the relief valve on the TC and the pressure was reading 78 PSI (third gear stall main brake engaged) - one thing of note, there were a couple shims already in the sleeve, as well as a washer ... Is there a max number of shims you should use? Anyway, I decided to test her out and made a couple passes and it heated up as usual ... I did notice that it stopped a bit quick after changing direction, so I went over to a hill and sure enough it wouldn't roll down it in neutral. I took off the floor plate and worked and cleaned all the linkages ... they seemed very good and free ... I was about to give up for the day and I took my little bar and tried to pry up on the main brake connector (don't know the exact term, but when you press on the main brake it engages on a plate. Well the plate went up a lot more than it ever did for me before ... I was likely too gently on it ... anyway it instantly started rolling in forward and reverse ... I pushed dirt for about half an hour and it didn't really even heat up to 100 deg C (90 deg F outside).... Could just a slight main brake friction cause such overheating? I did clean the linkages before, and it did roll pretty freely, but I can't remember if it rolled better or about the same... I guess my last couple questions would be.. 1. Should I be worried about my lower lube pressures? 2. Should I be worried about the amount of shimming in the TC relief valve? 3. How can I make sure that the main break doesn't stick, can I get heavier springs?
1. Maybe. 2. No, IMHO. 3. Brake dragging will cause heating in the powertrain oil - guaranteed. Maybe the next step ought to be a disassemble, clean, lubricate, reassemble, & adjust for the steering clutch & brake control linkages..? And while you're in there check for wear in the bushes and rod ends, of which there are many. There are 2 procedures for adjustment and it's not clear which one is relevant to your machine. I've included both. they are substantially different so it ought to be obvious which one of the two applies.
Thanks Nige - I will adjust and report back …… next weekend
Stabber,sounds like you are making progress.My gut feeling is still that there isn't too much wrong with it. Could you fix a strong spring to that brake pedal to make sure it isn't dragging and give it a good few hours working? I know it's abit red neck,but would perhaps cure it,then get it repaired properly
Maybe even replace the existing spring with a new one of the same Part Number. The existing one is 30+ years old by now, maybe it's getting a bit "tired"..?
Hi all, did we ever find out what was causing the D8L to overheat? I have a D8N with a similar problem and am having trouble figuring out what the issue is. Help needed!
I suggest that you should start a new thread. The D8L and D8N are totally different animals. The 8L has more in common with the 9N than it does with the 8N.(Cat changed the numbering system between the L & N series tractors, so the D8L became the D9N) When you do post information, please start with a Serial Number and then try to describe the symptoms in as much detail as you can along with what you have done so far to troubleshoot it.
Thanks for the advice Nige I am still testing a few things on the D8n but was just curious if stabber ever got to the cause of his heating problem
We had a D8L 53Y1864. Had the same problem with the transmission overheating. We put it on a slight incline to make sure it would roll in neutral to see if the brakes were hanging up. It would roll so we assumed that wasn't the problem. We check tranny cooler and it was clean. Decided that the only thing that would make that kind of heat was the converter. Pulled the converter and everything looked fine. resealed and reinstalled the converter. finally found the problem, the brake linkage wasn't releasing all the way and the overheating was caused by the brakes dragging. You could put the dozer in neutral and push it and it would roll but that little bit of drag was all it took to cause the problem. Removed and cleaned and lubes all the linkage and that corrected the problem
D8L, that's a big tractor for a farm. I bet she likes her fuel
I have a farm customer with a 9N and a 10N.