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Cooling Problem

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Chewy, Sep 25, 2000.

  1. Chewy

    Chewy 1/2 ton status

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    Here's the problem: I just bought a K5 and I noticed that it was running cold. I took off the thermostat cover and noticed that there wasn't a thermostat installed. So I put one in. But now it seems like it is not opening or there is air trapped in the system because now in a matter of a few short minutes, the engine temperature goes up to 260 and never cools off. I don't think it could be the water pump because I ran the engine without the radiator cap to try and get out any air and as it heated up it started shooting coolant out of the top of the radiator. Any thoughts or suggestions?

    '87 Beast
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Here's a stupid question, did you put the thermostat in right side up?
    I've done worse, and found that sometimes the obvious stuff gets ya [​IMG]

    Rene

    [​IMG]
     
  3. lowlevell

    lowlevell 1/2 ton status

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    I would also say that you put it in upside down.Unless you put a 6,000,000 degree thermostat in it=)
     
  4. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    It's not unheard of that a thermostat be bad out of the box. I always believe in checking the last thing you worked on when a problem crops up. The cooling system seems to be up to par since it was running cold without the thermostat. It may be that the waterpump is a high flow unit and it may be creating enough pressure to hold the thermostat closed. you might dry drilling {3/16 should be plenty} a bleed hole in the edge of the thermostat to equalize the pressure. Now another thing that may be causing a proble is a reach but possible. The truck is not overheating at all but there is cavitation forming around the temp sender and trapping a buble of steam. I had that happen on a 95. GM is aware of this problem and the cure is a TRW water pump that has a different flow rates. Another possible problem is you actully have a problem with mixture. With the engine running cold it would keep the computer in a cold start mode that would run the engine rich. If say you had a bad O2 sensor then when it kicked over to closed loop the truck could be leaning out real bad and would run hot as a result. If you don't know the miles on that O2 sensor it would be worth the $35 for a new one just for good measure regardless if it cures the problem. They have a 60k life expectancy. The FI engines are supose to run a bit warmer than the carb vehicles. About 210 is normal. The last thing to be concerned about is a possible blown head gaskets. If one was blown it would purge like you said it did. then the system would have air bubles traveling in the system that will not remove heat as well as coolant lowering the cooling capacity. Removing the thermostat may have broken the threshold where it could keep up with a BHG. Napa sells a kit for checking for exhaust in the coolant if you can't find the answer to the problem else where.

    Diging it in the dirt with my K5's
    Grim-Reaper
    http://grimsk5s.coloradok5.com/
     
  5. sosamantx

    sosamantx 1/2 ton status

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    <font color=blue>260 degrees?? I would have shut it down at 210-220 max., anything above 220+ is asking for serious problems. I agree with the orientation of the thermostat, is it installed correctly, with the spring down (pull off the top hose and look inside the thermostat housing). If you take off your radiator cap (when it is cold) and let the vehicle run, do you see the water circulating? You should see it move a little, you might have to give it a little gas to see it. Also how does the inside of the radiator look when you give it gas (the water level should drop down slightly), does it look clean or a lot of build up around the holes inside of the radiator? - Steve</font color=blue>

    <font color=blue>Steve Sosa a.k.a. "sosaman"</font color=blue>
    http://sosaman.home.texas.net/carpics.html
     
  6. Chewy

    Chewy 1/2 ton status

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    The thermostat is installed correctly. I've double checked myself a few times. I'll try some of these suggestions. Thanks a lot.

    '87 Beast
     
  7. sosamantx

    sosamantx 1/2 ton status

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    <font color=blue>Check your timing as well, I have always been told if the timing is too far advanced (or a tooth off on the distributor), that it will overheat. I have been reading in posts (I think some here, but elsewhere), they are saying that if the timing is retarded, that it will overheat. I have never really heard of this one, anyway, I don't think that it would affect it that much. - Steve</font color=blue>

    <font color=blue>Steve Sosa a.k.a. "sosaman"</font color=blue>
    http://sosaman.home.texas.net/carpics.html
     
  8. realsquash

    realsquash 1/2 ton status

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    Ahh, my timing was retarded (a lot) when i started my engine this spring for the first time. It was 32 degrees out and my headers turned completely red. I mean glowing red. Being a tooth off and running the engine at speed will overheat it, but it will run like crap, too.

    It's prolly something like you forgot to replenish the coolant or the thermostat is bad. It's always the easy/little things that getcha.

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  9. lowlevell

    lowlevell 1/2 ton status

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    Yes check the timing.I had the same prob with a ford.It was just a couple of degrees out of time and it ran very hot.But it always ran hot anyway....P.O.S.
     
  10. dumbfounded

    dumbfounded 1/2 ton status

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    If it didn't overheat without the thermostat then I wouldn't worry with the timing. Get a new thermostat and get a pot with water and a cooking thermometer and heat the water up till you see it open if it does at the right temp then install it. If you still have problems then check the timing and the water pump the impeller blades might be deteriorated (this happened to me)....

    Love, Peace, and Hair Grease...........
     
  11. Chewy

    Chewy 1/2 ton status

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    Drilling a hole in the thermostat worked great! Thanks to everyone for the input.

    '87 Beast
     
  12. sosamantx

    sosamantx 1/2 ton status

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    <font color=blue>You drilled a small hole on the housing? You probably had an air pocket in the system. - Steve</font color=blue>

    <font color=blue>Steve Sosa a.k.a. "sosaman"</font color=blue>
    http://sosaman.home.texas.net/carpics.html
     

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