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Hello, I have a 1987 Caterpillar D5H Dozer that after 1 hour of use the TC oil overheats. I had the TC rebuilt a few months back but the TC gauge still shows that it is overheating after 1 hour of use. I did not change the transmission oil cooler. Other than the overheating the Dozer operates just fine. It never loses power or slips even when the TC guage starts getting hot. I have checked all the pressures on the P1, P2 and TC test ports and the pressures are within specs according to the service manual. When I operate the Dozer I only push in 1st gear at a good rpm and it still overheats. If I back up or stop and let the machine just set and run the oil gauge doesn't cool down. If I let the machine set and idle at a really really low rpm, the oil gauge will drop to around 210 degrees F and just stay there but as soon as I start moving and just driving a very short distance without pushing any dirt, the gauge will jump right back up to 230-250 degrees F. Does anyone have any ideas what else could be causing the overheating issue. I would like to get the machine fixed so I can use it. Thanks Mike

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  • Ilike2fish Apr 06, 2015

    Hi Michael thank you for commenting on my question. i still have not fixed the dozer but i will do what you say and see if i can narrow it down. Is there anyway i can email you or talk to you over the phone about this issue?


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If the engins is not overheating then the source is most likely the transmission. Check oil level, bring engine to normal operating temp. Shift into 3rd. with the brakes applied blade firmly on the ground & at full RPM ( not more than 2 min. ) temp of T/C will begin to rise. At the same time observe the eng temp ( if it is rising rapidly before the T/C temp then there is a cooling problem with the engine cooling system which will affect the T/C temp) When the temp of the T/C is at approx 3/4 of the max temp range return sfift lever to netural with the throttle still at full and observe the T/C gage, If the needle dropes quickly the cooler is ok, if it don't you need to check the cooler circuit for restrictions. The next step if this does not indicate a problem with the cooler is to performe a stall test. You will need a tachometer for this and check with Caterpillar dealer or Cat mechanic to get the high idle & full load RPM specs. With tach installed run the engine at normal opperating temp, full throttle in neutral, it should be at full no load speed as per specs for the D5H engine +/- 50. Next with brakes applied in 3rd. gear blade firmely on the ground observe the tach if the speed is higher then specs. the torque converter is faulty, if lower than specs you need to adjust the fuel injection pump or check for engine low power. high RPM = possible internal wear in the T/C or lowT/C outlet or inlet pressures. if the outlet pressurs is determined by orifice in the outlet pipe from the T/C - check the transmission pump pressure. with suitable gage ( if none installed in your instrument panel which usually is ) run the engine at low idle observe the pressure then at Hi RPM observe the press it should be approx. no more than 30 PSI between low idle and high idle. Do the test in all speeds forward & 3 rd. reverse if there is a significant drop between any of the speed ranges or between for/ rev this will indicate a problem in the gear range or speed showing a lower than specs pressure. from my experiences it appears that either the transm pump or the torque converter is at fault. Check the transm strainer and filters for contamination. Alluminium = T/C problems. Steel, brass, iron, o-ring material and fiber = transmission problems. There are 52 causes for transmission overheating from tight tracks to engine related problems. Performing the stall test will narrow down the source of the problem. Good luck with your trouble shooting.

Posted on Apr 06, 2015

Testimonial: "Hi Michael thank you for commenting on my question. i still have not fixed the dozer but i will do what you say and see if i can narrow it down. Is there anyway i can email you or talk to you over the phone about this issue?"

  • 1 more comment 
  • Ilike2fish Apr 06, 2015

    Hi Michael thank you for commenting on my question. i still have not fixed the dozer but i will do what you say and see if i can narrow it down. Is there anyway i can email you or talk to you over the phone about this issue?"


    HI Mike I have spent the past 50 years as a Cat mechanic, instructor at Cat Dearle and Vocational Colledges, & Equip Maintenance consultant . My formost expereience is Power shift transmissiona & hydraulics. I now own and operate a business in Laos S.E. Asia. I would be happy to try and helo you out with your problem You Can e mail me at I suggest you try and follow the instructions I posted first so that if this do not determine your problem I can offer other suggestions. The stall test is one of the best ways to determine T/C problems, if the stall speed is high your defiently have converter problems could be as simple as low T/C inlet pressure or out let Pressure if the inlet pressure is ok and outlet low then most likely the transm punp is on it's way out or transmission main pressure setting too low . If your in dash transmission gage is not available or not working plumb into the pump test point and compare the pressure betweem lo idle and hi idle as i mentioned in the post.


    Steps to follow 1 - check oil level 2 - check strainer & filters 3 - bring engine and transm up to operating temp. 4 - check stall speed. 5 - check pressures - Initial press, P1, P2 & the T/C Inlet & Out let. wright down your findings if you were not able to determine the poblem so I can further assist you. I appears that you have some idea of what you are doing so I think you may be able to sort out the cause of your problem. since you stated the T/C was overhauled recently i think the problem is either the pump supply - low pressure restriction in the pump supply or the pump worn and output too low the outlet pressure would certainly be low if the pump supply is below specs. the press test at Hi/Lo rpm will geive you a good idea of pump condition.Calling a Cat dealer will cost a bundle and I think you can handle the job yourself Also let me know how and when the problem started if is was gradually on coming or happened over a very short time. The type of work you are doing with the dozer and type of material every bit of info will be helpfull. have the serial number also Good Luck.


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Check that the oil cooler fins are clean and not blocked for dust or dirt. Next check the oil flow through the cooler as it may be too high and not giving the oil a chance to exchange the heat to the air. You may have to insert a restriction in the return line to achieve this. Or conversely there may be a restriction from say a squashed oil line that is not allowing the oil to flow. Next suggestion is to talk with the caterpillar service technicians and find out why their machine is overheating. I am not sure but if you have a oil cooler inside the radiator maybe the water is running hotter than it should be. Check that the fan belts are tensioned correctly and are not slipping. To achieve this check that all the belts are the same tension and that one belt is not loose compared to the others.

Posted on Oct 14, 2013

  • Ilike2fish Oct 14, 2013

    Hi, thank you for posting. I took the oil cooler off and took it to a radiator shop and the guy was supposed to vat it and clean it. Im not sure if its clean though. It's an external cylinder shaped oil cooler that sits beside the motor. The water temp usually runs between 180F-190F and has never gotten over 200F even when the TC oil overheat light has came on. The TC light comes on at 260F.

    Let me refer u something I found on a forum. Here is it:

    A common failure on these transmissions is a spool and slug in the valve body that causes low flow through the converter and thus low flow to the cooler.
    Updated parts are avaliable.
    A pipe inside the transmission case can also crack causing the same problem and is replaced by a hose.
    check trnaspump pressure, converter in and out pressure.

    I'm not sure what valve and spool that the guy is talking about. Do you?


  • Bill Boyd Oct 15, 2013

    It seams logical that the forum writer has the answer.. have a talk to the catipillar service department and put it to them about the fix and any other problems associated wit over heating of the TC


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