Question about Cars & Trucks
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?"
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
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Posted on Jan 02, 2017
SOURCE: low idle in 1998 saturn sc1
I had this problem. Its a sensor. Unfortunately I don't remember the name of the sensor. When it gets a tiny litle crack in it, this is what happens. If you take it in to autozone, they will do a free sensor scan for you. You can replace it yourself. Its really no big deal. If you get the scan done you can contact me and I will give you further info.
Posted on Mar 16, 2009
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