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Thread: Cummins overheating help?

  1. #1
    Anyone have thoughts on why the temp on my Cummins will climb while under a good load? It's a '99 quad cab 4X4 with auto.
    Normal unloaded temp runs 190*. If I'm towing the 5th wheel, which weighs 12,000, and I stand on it hard to merge into traffic or to go up a hill, you can actually see the temp guage needle start climbing. I'm not pulling in overdrive, but if I switch the overdrive back on while on the flats, the temp starts dropping.
    It did this about 3 times last summer while double towing the 5th wheel and boat and got so high the warning bell sounded to "check guages" and the temp was right at 240*
    Radiator is at proper level with 50/50 mix, and the fins don't appear to be clogged with bugs.
    Any thoughts?

  2. #2
    I have a 97 Dodge 4x4 automatic with the Cummings engine. I've had the same problem, but to add more to that I've gone through 7 transmissions. A buddy thought that it might be the tranny causing the raise in temp because the tranny fluid runs through a seprate core in the same radiator. I've changed out the thermostat to a lower temp one, replaced the water pump, installed twin electric fans, and installed the biggest trans cooler for the tranny alone and it seems to work for the enigne. The tranny has been my biggest problem though. Also check your water pump. It might be starting to go. I hope this helps a bit.

  3. #3
    I had one with a very similar problem recently. I sent the radiator out to get cleaned, and blew out the condenser and intercooler. The truck does not overheat now. Try and just blow out everything out first and go from there.

  4. #4
    Thanks guys. I'll hit everything from the backside with the air compressor tonight and see what happens. Hopefully that will take care of the problem.

  5. #5
    We have an 01.5 and an 04 at our house.
    I would have the radiator recored with a bigger core and slip an electric fan or 2 on there and that should cure your ills. Have you checked the temp sending unit? That might be bad too.

  6. #6
    I think I found the problem. The radiator was/is pretty full of dirt and gunk. I looked down in between the radiator and intercooler and could see a big circle of that junk that coincided with the size of the fan shroud.
    I blew out as much as I could with the air compressor, but I was limited because of the space between the fan and radiator.
    I think I'm gonna have to take the radiator completely out to clean it.

  7. #7
    Maybe you can hit it with a pressure washer. It would save you the time and trouble of taking it out.

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