Please Help Cat D8L Transmission Overheating

[Nige]

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.

Thing is Ken, that compared to the cost of the replacement/repaired transmission the cost of a replacement cooler and a pump is peanuts.

 

[stabber]

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?

 

[stabber]

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?

 

[stabber]

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

 

[stabber]

There is a 53Y here in the UK literaly working today on the A9 Scotland

I miss Scotland! I lived / worked out of Aberdeen for 4 years! Had many a good night on Crown Street!

 

[stabber]

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 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

 

[Nige]

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 f**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.

 

[stabber]

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 f**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?

 

[Nige]

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.

 

[stabber]

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.

 

[Nige]

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...!

 

[Nige]

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.

 

[stabber]

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

 

[Nige]

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.?

 

[kshansen]

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.

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.

 

[Nige]

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.?

 

[Mark250]

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

 

[Nige]

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.

 

[RZucker]

Looks like "auto correct" is working overtime today.

 

[Nige]

That was my thought too. I just wanted clarification that what I think Mark was saying is what he actually meant.