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  1. #1

    Default Overheating issue in 2002 Chevy Silverado 1500 5.3 liter 4x4

    Been having this issue since last summer. I replaced thermostat 3 times (thinking a faulty one), fan does come on, checked for leaks with dye and UV light (only place I saw dye is out of overflow), did a chemical flush today...still no change. Only an issue when it gets over 75...then temp rises...I turn on heat to bring it down to normal and have to run with heat on. Not fun when it is heat index of over 100 out! Suggestions on what to try next?

    Sorry...didn't state what vehicle...2002 Chevy Silverado 1500 5.3 liter 4x4

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  3. #2

    Default

    Just a few items to check, since it overheats at high speed/high rpm the fan shouldnt be affecting things.
    Do you have a larger than stock bumper or a winch blocking airflow in the front?
    Is the radiator itself flowing coolant properly (this is suspect since turning on the heater helps the situation).
    Is the water pump flowing properly?
    You dont by any chance have larger than stock tires with factory gearing do you? This could be contributing to the problem.
    Has the cooling system been properly bled of all air, preferably with a vacume bleeder

  4. #3

    Default

    Quote Originally Posted by tbplus10 View Post
    Just a few items to check, since it overheats at high speed/high rpm the fan shouldnt be affecting things.
    Do you have a larger than stock bumper or a winch blocking airflow in the front?
    No
    Quote Originally Posted by tbplus10 View Post
    Is the radiator itself flowing coolant properly (this is suspect since turning on the heater helps the situation).
    How do I check that?
    Quote Originally Posted by tbplus10 View Post
    Is the water pump flowing properly?
    How do I check that?
    Quote Originally Posted by tbplus10 View Post
    You dont by any chance have larger than stock tires with factory gearing do you? This could be contributing to the problem.
    no
    Quote Originally Posted by tbplus10 View Post
    Has the cooling system been properly bled of all air, preferably with a vacume bleeder
    No...how do I do that?

  5. #4

    Default

    Bleeding the system can be done by going to your local Auto Zone or Napa and seeing if they have a radiator pressure check/Bleeder kit for loan or rent.
    Follow the normally included instructions.
    If there arent any included instructions the kit contains different caps to put on the radiator and or resevoir then you draw a vacume which should pull out any air in the system. Sometimes its easier if you park the vehicle with the front end raised a little and make sure you have the heater turned on to allow flow through the system.
    Radiator and water pump flow will probably need to be checked by a shop that has proper equipment. Many skilled mechanics can check the flow by pulling the cap and watching the water at idle but this isnt a tried and true method and can at times lead to mis diagnosys.

  6. #5

    Default

    Thank you! I will try bleeding the system first and take it from there.

  7. #6
    Legend

    Join Date
    Sep 2010
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    everett, massachusetts
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    Default

    Quote Originally Posted by Willow View Post
    Thank you! I will try bleeding the system first and take it from there.

    the proceedure to purge air from the coolant system with these vehicles is to remove the coolant pressure cap at the plastic coolant fill container when the engine is cold. the start engine and continue to run engine until it is at normal operating temp. then increase RPM to 2000 and hold for about 30 seconds. repeat a few times. if you had air in the system the coolant level will drop.

    the other reason you may have overheating during warm/hot weather is a defective coolant pressure cap. if you find when it over heats the coolant hoses are not hard/pressure in them then this is what happens. reason is when NOT under pressure the coolant will boil. when that happens the water pump cannot pump air bubbles and then the over heating.

    if you lived in a very high elevation this is more so an issue that the coolant system must be under pressure. since the lower the pressure the lower the temp that the coolant will boil.

    now another thing that causes air bubbles would be exhaust gases entering the coolant system . that would be a bad day.

  8. #7

    Default

    OK...checked to see if hose gets hard when hot...it does get harder (I can squeeze a bit so not sure if that is correct or not). Went and rented a pressure tester from auto zone...I can't get it to seal. I am using the adapter that does fit. The instructions inside are pretty useless. At first thought faulty tool...then went back and they gave me a new one in box...now that makes some noise when you pump but no pressure build up. I am sure I am not doing something right as it does hold at least some pressure (I tried to take cap off before it was cool enough and it was boiling and going trough overflow when I loosened). Guess I will do a video search for a test being done to figure out what I am doing wrong. Now when I pump it...what should I pump it up to? I assume at some point I need to start vehicle...when? How long to run? Maybe all that will be int he video. Sigh- a mechanic I am not.

    - - - Updated - - -

    OK...not having any luck finding more info to see if I hooked this up wrong. From the single photo I saw of one hooked up to a radiator...looks the same as what it did when I had it hooked up to my truck...so why no pressure building when I pump it?

  9. #8

    Default

    Should be drawing a vacume, not building pressure.

  10. #9
    Legend

    Join Date
    Sep 2010
    Location
    everett, massachusetts
    Posts
    1,491

    Default

    call an Auto Zone in your area and ask if they can help with the pressure tester you have for proper procedure . If with proper hook up/testing no pressure then you now know why it has this problem. finding the leak can be tough especially if you have a head gasket leak. also the water pump gaskets are a well known leak with these.

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  12. #10

    Default

    OK...I was putting in on right...the problem was no seal because of the overflow...when I pumped it- air coming out of the overflow tube. Pinched the tube and pumped up to 15 lbs and it held....didn't budge in 10 mins. Thinking cap not allowing pressure to build so when I brought kit back I bought a cap. Will find out tomorrow if that fixed it. If not- freind said to take off thermostat and run without it and see if I still have issue. If so- I would assume thermostat bad (guess it is possible to get 2 bad ones). If not...guess the next step would be to replace radiator (since pulling it out and having it acid washed will cost me anyhow- may as well replace it)?

    - - - Updated - - -

    Quote Originally Posted by tbplus10 View Post
    Should be drawing a vacume, not building pressure.
    All i know is you pump it until the gauge reads 15 lbs...I assume that is pressure and not vaccuum...I could be wrong though.

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