20R overheating... Possibly bad Radiator?

Discussion in 'Maintenance/Repair' started by Jonathan Warren, Dec 26, 2020.

  1. Jonathan Warren

    Jonathan Warren Newbie

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    So I have recently experienced some engine overheating problems. Everything was fine but I woke up one morning, hopped in the truck and drove less than a quarter mile down the road before it tacked out the thermostat. I thought it was a sticky thermostat, so I took it out, replaced it, same problem. Now the truck runs hot with a thermostat and runs cool without the thermostat, seems backwards right? Also, the upper radiator hose builds pressure and gets almost rock solid before the thermostat opens up but as soon as the thermostat opens the hose loosens and is fine after that. The only reason I question this is because I originally thought "Blown head gasket or possibly a leak into a cylinder?", but that scratched that idea. Obviously if it was a blown head gasket, it would eventually build up pressure once the engine gets really hot , but it never did. I ran the truck without a cap to check for burps and air bubbles, and it seemed to burp a lot more than it probably should be burping, so, that also leads me to think "Head gasket leak". But at the same time, while I had the radiator cap off (while running at idle) I noticed that there was literally NO water flow from the upper radiator hose (left side of radiator) to the lower radiator hose (right side of radiator). Possibly a clogged? Everything seems to be acting pretty backwards to me, so I am hoping that someone can shed some light on this, thanks in advance! :)
     
  2. Liquidhandwash

    Liquidhandwash Enthusiast

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    There are only a hand full of things that cause overheating, just work your way through them,
    Airflow through the radiator (fan not working or crap in the core blocked up with grass)
    Water flow through the radiator ( blocked radiator, failed thermostat, failed water pump, airlock)
    loss of coolant (due to leak or head gasket, cracked head etc)
    You can check for a blocked radiator by removing the thermostat and radiator cap fill it with water and give the engine a big rev. If the water leaps out of the radiator and bottom hose get sucked flat it's blocked.
    Most likely its ahead problem, borrow a coolant system pressure test it will soon tell you if you have a problem.
    P.S. some time the impeller on the water pump can drop off, very rare but if all else fails..
     
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  3. MrDinkleman

    MrDinkleman Addict

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    First of all, why do you think it's backwards when the engine runs hot with a thermostat and runs cool without a thermostat? That's actually normal. The thermostat is there to maintain a steady temperature of 190degrees or so. Without it, the engine will run too cool. Bad for gas mileage. Sounds like your engine is fine to me.

    Secondly, brand new thermostats CAN be defective. I once went through TWO brand new OEM thermostats in a row that did not open correctly. Same symptoms as yours. I would see temp climb up over 200degrees then suddenly drop and everything would be fine. That your new thermostat opens up eventually and everything runs fine sounds like it's sticking as well. I would say either test your new thermostat or just try buying another...

    Finally, are you sure you installed the thermostat right side up? And yeah, I made sure the two defective thermostats were installed right side up before buying a third one that worked...
     
    Last edited: Dec 27, 2020
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  4. Jonathan Warren

    Jonathan Warren Newbie

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    I love this community so much... XD lol just went and took the thermostat out and took the cap off, rev'ed the engine, and the lower hose collapsed as water shot out the top of the radiator. I have never heard of such a thing, but after thinking about it, it makes total sense!! thanks for the info brother! :)
     
  5. Liquidhandwash

    Liquidhandwash Enthusiast

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    happy to help, make sure you flush the engine as well as the radiator, there is likely crap inside the engine as well, which will block you new radiator up very quickly..... don't ask how I know this..
     
  6. Jonathan Warren

    Jonathan Warren Newbie

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    affirmative! what are the chances of flushing the current radiator and possibly doing an engine flush to save the radiator I already have? I would like to save the one I have because trying to find a new radiator that is an exact bolt up fit im finding to be... a little challenging... lol
     
  7. Liquidhandwash

    Liquidhandwash Enthusiast

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    You may be able to flush it out with a hose, just depends on how bad it is, remove the radiator and turn upside down and put the hose in the bottom tank, wrap a rag around the hose will help with sealing. A little compressed air with the water also helps if you have a compressor. If it is really blocked you may have to take the radiator in to have the tanks removed and the core cleaned out properly.
    To flush the engine put the hose in the to radiator hose with the thermostat removed, again if you can get some compressed air in there with the water it helps. You can then put it in the bottom hose and repeat, then back to the top hose again, repeat until the water runs cleanly with a blast of compressed air. While you're at it flush the heater core by removing the hoses and flushing the reverse direction of the normal coolant flow.
     
  8. Justin Danger

    Justin Danger Toyotaholic

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    I remember my first truck had a radiator that was clogged up with stop-leak. When I flushed it and cleared it out, i found the leak! So watch out for what you might find.
     

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