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2001 Tahoe Reverse Flow cooling system

Discussion in 'Engine & Drivetrain' started by LanceLyons, Oct 17, 2020.

  1. LanceLyons

    LanceLyons TYF Newbie

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    Hi, I think my tahoe has a reverse flow kooling system. The thermostat is on the lower radiator line.

    after flushing, draining, and cleaning radiator, toping it back off with dexcool, burping ,etc I noticed that the engine would heat up to 190 (tsat temp) and hold for a minute before moving up to 230-250 fairly quickly. I repeatedly tried to get the air out by running the engine with the reservoir cap off watching and hoping the air would come out.

    finally after doing this a half dozen times with no improvement I decided to poor coolant in the upper hose back filling into the motor. I pored a half gallon in it seemed.

    the next time I ran the engine it was back to normal. tstat holding at 190. have driven it 50 miles already in the last 2 days with no problems.

    could it be the water pump didnt have any liquid to pump and therefore i had no coolant circulation in the engine? Or do I still have a problem and just fixed it temporarily?

    if anybody has a drawing of the tahoe 4.8 l reverse coolant flow, I would love to see it.

    thanks in advance.

    Lance
     
  2. Scottydoggs

    Scottydoggs Full Access Member

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    if it took coolant in the top hose into the engine you had air trapped, thats why it got hot fast.
     
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  3. LanceLyons

    LanceLyons TYF Newbie

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    I agree but taking off the top hose to get coolant into the system doesnt seem like a good design. How do you normally get the coolant into the motor after flushing and draining? I understand they say put in reservoir and run with the cap off a little and repeat but I did that more than a dozen times.
     
  4. Larryjb

    Larryjb Full Access Member

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    The 5.3 has the same basic cooling design having the thermostat at the bottom. I have drained and refilled my system at least 3 times so far. I had no trouble at all.

    Were you squeezing the upper rad hose with the engine running? Was the upper rad hose hot? I agree with Scott, you had an air lock.
     
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  5. Fless

    Fless Full Access Member

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    LS1waterpump.jpg
     
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  6. Larryjb

    Larryjb Full Access Member

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    I like this guy:
     
  7. Scottydoggs

    Scottydoggs Full Access Member

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    its just one of them things, my last car had a 3800, t stat was in the lim and they used to get air locked some times. when you fill it from the top your pushing all the air up and out. so thats the fix pretty much.
     
  8. LanceLyons

    LanceLyons TYF Newbie

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    First thanks guys.. Much appreciated.

    I thought that it was too simple that adding into the upper hose was a temporary situation. I drove it around a bit more this weekend and it did fine until I idled in a parking lot for about 10 minutes and the temp pegged out.


    I will say that I started moving (driving back to the house) and the temperatures came back down to tstat temps. Now this typically tells me the radiator or fan or flow rate is not proper. I did clean the radiator several weeks back (take it out and clean) and I was able to run a garden hose and had good flow through the radiator. I tested the tstat and it opens about 1/4 inch. My clutch fan seems good as it doesnt spin much when you try to spin it (it doesnt give to much). I do notice that I dont get consistent heat out of the heater core.

    Is this flow? Is this radiator? What am I missing here.
     
  9. Larryjb

    Larryjb Full Access Member

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    How old is your water pump?

    I think that, unless the cooling system was horribly neglected, I kind of doubt the radiator is plugged internally.
     
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  10. Doubeleive

    Doubeleive Supporting Member

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    my first suspect would be the radiator, if it is over 5 years old then it's time to replace it, yes you might get flow in and out, that doesn't mean it is cooling properly the little fins can be clogged especially if it has not been maintained annually. the fact that it works ok with good air flow and not when just idling is a dead giveaway. just my opinion also when you cleaned it out do you think you might have removed the restrictor to the reservoir tank? take a look at the flow from the radiator to the reservoir if you see liquid moving quickly that is also a known problem.
     
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