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Last Cooling Question...I Hope!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Bowtied, Aug 21, 2001.

  1. Bowtied

    Bowtied Registered Member

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    Okay, hopefully this will be the final cooling question. I spoke too soon last week when I said my truck was fixed. It WILL run nice and cool now, about 165 with the pedal down and the A/C on. BUT on initial start-up (with the engine cool) it will first climb up to 260 (this takes a few minutes), it will stay there for a few seconds, and then BAM, it'll fall like a rock and stop right on 165 and will stay there for as long as I run the truck.

    I first discovered this while on my way to N.C. last week. At first I found that If I let it get to 260, pop it up in N and kill the engine, I would immediatly hear it bubbling (boiling) off in the expansion tank. I'd let it bubble off for about 6 or 7 seconds and then crank it back up and she'd go right to 165. I could shut it off and restart it without having to "burp" it as long as it wasn't long enough for the engine to cool. But if it was any longer than 10 or 15 minutes I'd have to "burp" it again. So for most of the trip down and back I just did'nt shut it off, I'd let it run for 7 hours and it never went above 165-170.

    Later I found that if I just let the engine run it would go to 260, stay there for a second, and then come back down on it's own.

    So, that's where I'm at now. Tonight I put in another t-stat(195) and let it run without the cap on for about 20 minutes to hopefully purge any air remaining in the system. Then I let it cool and when I fired it up, same thing, 260...165.

    Just to update anyone who hasent read my previous posts I'll list whats been checked and changed already.
    New Rad
    New Rad Cap
    New Hoses
    Multiple New T-stats (195, checked in boiling water, installed "V" pointing up / button down.)
    New Water Pump (I did double check the part number to make sure I had the correct one.)
    New Extra Heavy Duty Fan Clutch (serious suction!!!)
    And finally, the temp gauge in the truck IS reading accurately (checked with temp probe.)


    As Always, ANY help would be greatly appreciated!!!

    Thanks,
    Andy
     
  2. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Wow... sounds like you have really covered your bases! I bet that SOMEHOW you still have a bubble... if you have to burp it, then it has air in the engine. That simple.

    Now how you get it out...I always run the truck without the cap (like you have) and then I will "pop" the throttle a bunch of times to get the pump shuffling that water along. Just run the hose into the radiator slowly whenever it needs more water.

    Finally, hold the RPM up to 2500-3000RPM just enough to make the water level drop in the radiator. Fill 'er up with the throttle running high, and then cap it off once its full. (You will need a friend to help you out...)

    This is all I can suggest. I'm sure at this point you will try anything. GOOD LUCK!

    <font color=red>GOT MUD???</font color=red>
    454/TH400/NP205 - 14BFF/D60/w/ 4.10s
    <a target="_blank" href=http://24.10.209.54/bigolk5.htm>http://24.10.209.54/bigolk5.htm</a> [​IMG]
     
  3. RESTORE89

    RESTORE89 1/2 ton status

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    i agree sounds like you still have a bubble in there somewhere
    dont ask me how to get it out
    maybe the guy at teh shop you took it to last time could help with just a phone call

    It needs a bigger motor.
    what's in it now?
    doen't matter it NEEDS A BIGGER MOTOR
    89 350tbi/700r4h/np208/4.11's
     
  4. RESTORE89

    RESTORE89 1/2 ton status

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    another thought
    could it be the sending unit is acting up
    sounds like it shows cooling down way to fast try using your remote temp gauge at start up and double chack that it really is hitting that high temp
    man i feel for you
    i have been chasing a strange feeling steering issue for awhile myself
    good luck

    It needs a bigger motor.
    what's in it now?
    doen't matter it NEEDS A BIGGER MOTOR
    89 350tbi/700r4h/np208/4.11's
     
  5. Itali83

    Itali83 1/2 ton status

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    NEVER trust factory guages. Just splurge and get a good mechanical one. THey don't lie.
    Ben 87 Jimmy
    <font color=blue>Rust=Bad</font color=blue>
    <a target="_blank" href=http://www.bens87toy.alloffroad.com>www.bens87toy.alloffroad.com</a>
     
  6. Pugsley

    Pugsley 1/2 ton status

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    If you don't already have one installed, get one of the little Prestone flush/fill kits, and fill your system through it while the engine's running. Usually you can exorcise any leftover bubbles this way.

    Dos mas Tecates!!!
    <a target="_blank" href=http://pugsley.alloffroad.com>pugsley.alloffroad.com</a>
     
  7. newyorkin

    newyorkin 1 ton status

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    I hate to sound like a broken record and I may have missed the answer if you posted it, but is the flow going the right way? To motor through bottom hose, from motor through top hose? The pump may be right, but is this the stock motor and belt routing? If it's wrong, the pump will suck all the water out of the engine, creating a big air bubble until the air around the stat gets hot enough to open it and let some coolant flow through.
    That all may be barking up the wrong tree still, but did you try drilling a small bleeder hole in flange of the stat? try that, maybe it'll at least tell you if air is still the problem.
    Also, remember everything that changed since it was running nice and cool (normal; after the flush).
    Geez man, watch out with these temps! I hope this clears up soon!

    Ratch
    <a target="_blank" href=http://k5.8m.com>k5.8m.com</a>
    **Ever stop to think... Then forget to start again?**
     
  8. CaptCrunch

    CaptCrunch 1/2 ton status

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    I agre... get a flushing tee if you haven't... sounds like an air bubble... double check that you don't have bubbles forming as you run it... bubbling from the radiator can becaused by a leak in the system... usually if it isn't externally visable it is a intake or head gasket leak. Also get a aftermarket thermometer or take it uup to a local place and have a technician shoot it w/ his laser temp reader.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
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