Hi Team, I am at stuck with an overheating transmission on a Cat D8N 5TJ503. Torque converter outlet temp will get to 130 degrees C just from tracking, without load on the trans, in all gears. Machine stays cool in the morning (10 degrees C higher than engine) but as the day goes on it gets up to around 130 degrees C. The engine coolant temp stays around 90 degrees C. The temperature will lower slowly at raised idle. Torque converter outlet spec is 60PSI +- 10PSI, i have removed shims and lowered outlet pressure to 50PSI from 60PSI, in the hope to allow more oil to flow through cooler. Lube pressure is 20PSI at high idle warm (100 degrees C) oil Removed torque converter scavenge line and caught 3L oil. I have checked temps with temp gun and they are similar to gauge. Machine seems to operate perfectly apart from overheating. Brakes don't seem to be dragging. Running 30W transmission fluid in 32 degree C ambient temperature. Oil samples come back clean. Previous repairs. Oil cooler replaced 5 years ago. Because of overheating issue. Trans pump replaced 5 years ago. Because of overheating issue. I have pulled the cooler again last week and it is spotless. Lines all are clear. I am open to any ideas? .... Please
What are the temps you measured for:- 1. Radiator coolant inlet/outlet 2. Trans cooler coolant inlet/outlet 3. Trans cooler oil inlet/outet
As with ANY overheating problem............verify that your machine system is actually overheating. So many times, it can be simply a faulty sensor, gauge, or sender.
I will record my results with the temp gun today and get back to you I have swapped the transmission temperature gauge and the sensors. The transmission is still reading the same on the gauge.
I used a temp gun and checked the temps. I pulled the machine up before it got too hot. The trans gauge was reading 120 degrees C (I forgot to take a reading at the converter outlet) 105 degrees C at top of cooler 96.5 degrees C at bottom of cooler 98 degrees C at top radiator hose 89 degrees C at bottom radiator hose The trans overheated first and brought the engine up, I gave the radiator and good clean again yesterday and the operator reported it overheated again today at anything over half RPM. He is tracking in second gear and it is enough to cause it to overheat. I will be back there in a few days to take more temp readings as Nige described.
If the top of the cooler is reading 105c / 221 f when the gauge reads 120c / 248f I would suspect the gauge is reading higher than the actual temp because the line to the top of the cooler comes directly from the converter outlet. 105 is not overheated for a d8n trans. They always run high temps. If the trans temp light isn’t coming on it’s not hot yet. The light is on a separate temp switch.
Wot he said.........^^^^^^^^^ A few snippets of data. The 3T-5825 temp switch (Normally Closed) that lights the high TC Out temp warning on the Monitor Panel has the following specs. Opens/actuates at 129.4 ± 2.8°C with rising temperature and deactuates at 118.3°C MIN with falling temperature. The 7N-9785 temp switch (NC) for the coolant opens/actuates at 107.2 ± 2.8°C with rising temperature and deactuates at 91 .0°C MIN with falling temperature. Your 9 DegC difference between radiator inlet and outlet is just about bang on the money. A radiator in perfect condition is only expected to have a 10 Deg difference between inlet and outlet.
A good test of how well the power train oil cooler is working is to watch the recovery of TC Out temperature after a push. For this you will probably have to run the machine yourself rather than rely on the operator's word. As the machine is pushing a blade full of dirt it's perfectly normal for the converter temp to rise. At the end of the push the converter temp should rapidly start falling when the load comes off and the transmission is shifted to reverse. The temp should fall rapidly towards whatever the coolant temp is, the closer it gets to coolant temp the slower the fall on converter temp will be, if that makes sense. Try that and report your findings.
Yes,I’m starting to think the OP needs to be in the seat for a few hours from a cold start and pre check