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  1. #11

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    Ok you were pressure testing the system for leaks, if your bleeding the system of air you draw vacume.
    Many shops no longer boil out radiators, one reason is all the plastic parts, another is its just as cheap to replace the radiator.

  2. #12
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    Quote Originally Posted by Willow View Post
    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 - - -


    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.
    sounds good now that it may just be a bad cap and that would be a cheap fix.

    it is possible you got a bad thermostat. but if the temp is bad with all 3 thermostats you had in there, with the exact same issue I doubt it.

  3. #13

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    I agree with @j cat, 3 bad t-stats is not a likely scenario. The cap may be the problem, but it works at slow speeds and driving around town. That's when it should be overheating, highway speed should be "driving" sufficient cooling air through the radiator to keep it cool even if the fan wasn't working.

    Are you carrying any heavy loads, or towing?
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  4. #14
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    Quote Originally Posted by RayVoy View Post
    I agree with @j cat, 3 bad t-stats is not a likely scenario. The cap may be the problem, but it works at slow speeds and driving around town. That's when it should be overheating, highway speed should be "driving" sufficient cooling air through the radiator to keep it cool even if the fan wasn't working.

    Are you carrying any heavy loads, or towing?
    the cap if bad will create this condition at all speeds with the higher temps. also the higher you go in elevation the more so this will occur .

    when on the hyway your loading up the engine much more than driving @ 30MPH.

    if he had a bad fan clutch this is more vehicle speed . at slow speeds the engine would run hotter than hywy speeds.

  5. #15
    Jr. Apprentice
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    I had an overheat condition yesterday while sitting in traffic, so I turned on the heat up all the way and got off the road until it cooled off. I checked the coolant which was low and added more. In addition to being low on coolant what I thought was curious was the fact that I didn't hear the fan running like I sometimes do just while driving around. I wonder what that was all about.
    2004 GMC Sierra SLT Z71, Truxedo Low Pro QT tonneau cover, Rhinoliner bed liner, Putco side rails, Weathertech window deflectors and floor mats, AMP Research bed extender, GMC cloth seat covers, light bar, lights and more to come.

  6. #16
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    Quote Originally Posted by SEMiller View Post
    I had an overheat condition yesterday while sitting in traffic, so I turned on the heat up all the way and got off the road until it cooled off. I checked the coolant which was low and added more. In addition to being low on coolant what I thought was curious was the fact that I didn't hear the fan running like I sometimes do just while driving around. I wonder what that was all about.
    if you were low on the coolant you most likely have a leak. check the water pump area for leaking at the engine pump gaskets also the heater hoses etc..

  7. #17

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    Quote Originally Posted by j cat View Post
    the cap if bad will create this condition at all speeds with the higher temps. also the higher you go in elevation the more so this will occur .

    when on the hyway your loading up the engine much more than driving @ 30MPH.

    if he had a bad fan clutch this is more vehicle speed . at slow speeds the engine would run hotter than hywy speeds.
    Yeah, I agree j cat, that's why I said "but it works at slow speeds and driving around town."
    What I find strange, is that blowing air across the heater core is enough to bring the temps back to normal. That's a small core and a small amount of air to fix the problem; not to mention, the small hose capacity that feeds the heater core.

    I wonder if the gauge is reading correctly.

    Quote Originally Posted by SEMiller View Post
    what I thought was curious was the fact that I didn't hear the fan running like I sometimes do just while driving around..
    I assume, he is talking about the radiator fan. If he can hear it, usually indicates a problem. If the clutch is working correctly, the fan should not make a lot of noise.

    I'm suspecting the fan clutch needs to be replaced. Or, perhaps the fan clutch relay may be failing from time to time.

  8. #18

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    OK...cap did not fix it (knew that would be too easy). Stopped at the repair shop I use...they think air flow issue and suggested I pressure wash the front of the radiator even though they said it appeared reasonably clean, said bugs can get in there and block the air flow. So after work, stopped at a car wash and blasted it for about 15 mins. sticking wand into the grill. Did not fix issue. Now I do have a spectre air intake system on it.....that I put on almost a year ago...but I was having issue before that was put on.
    RayVoy- no, not towing or carrying anything (other than my tiny little self).

    TBPlus...not sure what drawing air out of the system would do as I had to pinch the overflow hose just to get vacuum....soon as I would unpinch hose...air would come in as well as when I took off the pump and replaced cap. I did not see any options for vacuum on this pump either....it was a pretty simple kit from AutoZone.

    Jcat- I agree. I doubt it is the thermostat. Just saying what my friend suggested to try- I am running out of things to try here. BTW I am a she

    Someone mentioned defective gauge? Now that may be a possibility. I have been having issue with my fuel gauge (been writing down how many miles to put in gas so I don't run out- I figure at 16 mpg to be on safe side and when I fill up I end up being pleasantly surprised). BUT if that was the case would it not also do that in cooler weather and not drop when I turn on heat?

    What would you all try next? I am now scratching my head.
    Last edited by Willow; 07-26-2013 at 06:34 PM.

  9. #19
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    Quote Originally Posted by j cat View Post
    if you were low on the coolant you most likely have a leak. check the water pump area for leaking at the engine pump gaskets also the heater hoses etc..
    I took a quick look under the hood and didn't see any wetness around the water pump or hoses. The truck has to go in for an inspection in August, I'll have my mechanic do a coolant flush and check that out.

  10. #20

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    Hi Willow, looks like someone tagged along on your thread, I answered him (?) in my previous post thinking it was you.

    But, that answer may fix your problem as well. I suggested a problem with the radiator fan clutch. He could hear his (not normal), but yours may not be working, therefore the fan does not engage and the fan blades don't spin.

    It should throw a check engine code and light the CEL (check engine light), but it may be worth a try.
    With the engine turned OFF, try to turn the radiator fan blades. Try it when engine is hot, and when cold. Don't force it, you could bend a blade.

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