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I’ve had it with over heating!!!

Discussion in '3rd Gen 4Runners (1996-2002)' started by skurtydurty, Apr 5, 2020.

  1. Apr 5, 2020 at 11:17 AM
    #1
    skurtydurty

    skurtydurty [OP] New Member

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    So, I bought my 4Runner a few months back. It wasn’t running when I got it. Since day one it’s been over heating and I have absolutely no clue what the hell is going on. I’m really at wits end. The previous owner said he replaced the timing belt and water pump. So this is what’s happening.

    I bought a champion cooling systems radiator CC1998. I bought a thermostat from the dealer. I replaced the thermostat. I’ve tried 3 of them. No matter what I do it doesn’t seem to open up. I’ve burped the system and took the top hose off to fill the cooling system up from the engine side. Jiggle valve is at 6 o’clock but no matter what the bottom hose is always cold. It’ll even get to the point that the coolant will begin to boil before it’ll open up. Ive put the front of the 4R on ramps and tried to burp the system but it’s still over heating. The thing that’s stupid is that if I take the thermostat out. It runs cold... so I know it’s flowing. I’m at a huge loss and really just want my 4R back and running. If anyone has some insight I’d really appreciate it.
     
  2. Apr 5, 2020 at 12:10 PM
    #2
    scottalot

    scottalot Stockalot

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    To be determined
    Sure you’re not installing the thermostat upside down?
     
  3. Apr 5, 2020 at 12:13 PM
    #3
    skurtydurty

    skurtydurty [OP] New Member

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    The thermostat only goes in one way. Every thread I’ve read about coolant systems says jiggle valve at 6 o clock. That’s what I’ve done.
     
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  4. Apr 5, 2020 at 12:15 PM
    #4
    scottalot

    scottalot Stockalot

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    To be determined
    Haven’t worked on one personably but have heard of people flipping the thermostat on other vehicles before.
    Definitely sounds like something simple is stumping ya if it runs cold when you pull the thermostat but hot with it in.
     
  5. Apr 5, 2020 at 12:17 PM
    #5
    scottalot

    scottalot Stockalot

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    To be determined
    For giggles why not rig the thermostat to stay open and reinstall it. See if it runs closer to a normal temp and then narrow down the issue
     
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  6. Apr 5, 2020 at 12:18 PM
    #6
    skurtydurty

    skurtydurty [OP] New Member

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    That’s what I’m thinking. It has to be something simple I’m overlooking.
     
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  7. Apr 5, 2020 at 12:23 PM
    #7
    SlvrSlug

    SlvrSlug Slightly bent.

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    Boil some water on the stove, and drop it in see if it opens.
     
  8. Apr 5, 2020 at 12:58 PM
    #8
    skurtydurty

    skurtydurty [OP] New Member

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    Just tested all the thermostats I have. They all opened up before the water started a rolling boil.
     
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  9. Apr 5, 2020 at 4:39 PM
    #9
    negusm

    negusm New Member

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    Bad head gasket/cracked head. Exhaust getting into the coolant will do EXACTLY what you are describing.
     
  10. Apr 5, 2020 at 5:11 PM
    #10
    scottalot

    scottalot Stockalot

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    To be determined
    :pray: That’s not the case
     
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  11. Apr 5, 2020 at 5:57 PM
    #11
    skurtydurty

    skurtydurty [OP] New Member

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    I’m reading around other threads and thats what seems to be the culprit in my case. It doesn’t start bubbling immediately it takes time for it to start bubbling. It won’t over heat if I’m just sitting but under any kind of load it’ll begin to over heat big time.
     
  12. Apr 5, 2020 at 6:17 PM
    #12
    Dark Knight

    Dark Knight Get off my lawn

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    Bubbling? You see/hear bubbles in the coolant overflow tank?
     
  13. Apr 5, 2020 at 6:51 PM
    #13
    skurtydurty

    skurtydurty [OP] New Member

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    I can feel bubbles in the top hose after it reaches running temperature. And yes it’s a rolling bubble in the overflow tank.
     
  14. Apr 5, 2020 at 7:00 PM
    #14
    Dark Knight

    Dark Knight Get off my lawn

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    Like negusm said. Head gasket.

    I had those same symptoms on my 2005 4.0 when it blew a head gasket.
     
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  15. Apr 5, 2020 at 7:41 PM
    #15
    skurtydurty

    skurtydurty [OP] New Member

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    I’m gonna start looking into it. I need to do a leak down test and see where I’ve got a leak.
     
  16. Apr 5, 2020 at 8:41 PM
    #16
    4x Old Guy

    4x Old Guy New Member

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    Boiling the thermostats is the correct diagnostic procedure to determine whether or not the ‘stat is actually working. You can also put a cooking thermometer in the “soup” at the same time to verify the actual temperature that the thermostat is opening. The thermostat should open completely (spring is pretty much completely “squashed”) before the water starts boiling.

    When installing a thermostat, the coiled spring on the thermostat goes toward the engine block.

    The little hole with the dangling little metal valve is there to allow a very small amount of coolant to flow through the thermostat so that can accurately sense the coolant temperature, and also allow any air to get by the thermostat to help purge the system.

    Borrow a cooling system pressure checker from the local parts place (you “buy” it up front, then they refund your money when you return it with the idea that you’ll buy some parts from them). Fill the system up completely and use the pressure checker to pressurize the cold system to whatever the stock pressure cap is rated at. Then sit and watch the pressure gauge. The pressure should not drop at all. If it does drop, then you’ve got a leak somewhere.

    If it does leak, pump it up a few more times and look to see if any coolant is dripping out somewhere (probably not, but it’s worth a quick look).

    If the head gasket is what is leaking, the coolant will most likely be seeping into one of the cylinders. To find out which cylinder, remove all the spark plugs, then briefly crank the engine over. The leaked coolant should come flying out of the plug hole of the cylinder that has the bad head gasket.

    Good luck.
     
    Last edited: Apr 5, 2020
    jmkulbeth, negusm, scottalot and 2 others like this.
  17. Apr 13, 2020 at 9:23 AM
    #17
    DesertRoads

    DesertRoads New Member

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    If you've already tried new thermostats, have you considered doing a compression check? That might rule out the other issues of blown head gasket and/or cracked block.
     
  18. Oct 18, 2021 at 5:31 PM
    #18
    krat65

    krat65 New Member

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    I'm really interested on what happened here. I have the same story, I bought a 2001 4Runner and was told the water pump was redone. It was running cold so I looked and no thermostat. I put in a new thermostat and it overheated. I tested it in a pot of water and it opened at 180. I replaced the fan clutch and radiator (mostly because they where cheap and ruled out a plugged radiator). When the thermostat is installed and under load it overheats. The heater core is good and blows hot with thermostat in. I have not done a pressure test yet but thinking that will be my next stop. When burping the system i do get bubbles at idle but when I throttle up it seems just to be moving fluid.
     
  19. Oct 18, 2021 at 5:43 PM
    #19
    Doubleduty

    Doubleduty Life is better on the mountain

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    My guess is also the fan clutch. Not a very expensive fix, that is , if you haven't already ruled it out.
    Other than that, a clogged radiator, or water pump.
    Let us know what you find. Don't stress on it! Probably not major.
     
  20. Oct 18, 2021 at 6:19 PM
    #20
    krat65

    krat65 New Member

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    Oh, I did the fan clutch with the radiator. Normally it's not something bigger but I'm out of easy cheap fix's and looking that the head gasket or block is the culprit.
     
  21. Oct 18, 2021 at 6:26 PM
    #21
    Doubleduty

    Doubleduty Life is better on the mountain

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    Water pump?
    Heater core?
     
  22. Oct 18, 2021 at 6:45 PM
    #22
    krat65

    krat65 New Member

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    The heater core is fine, blows hot when the thermostat is in and no leaks. The water pump was supposedly replace before I purchased it. Looking like the guy who I bought it from might have know there was a bigger issue once he replace the water pump, maybe the reason he removed the thermostat.
     
  23. Oct 18, 2021 at 6:52 PM
    #23
    Doubleduty

    Doubleduty Life is better on the mountain

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    Seems like the only other thing, could be a cracked head...hope not, but not the end of the world if so.
    Sounds like you've ruled out the little things like thermostat, water pump and radiator? Here to help , if we can.
     
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  24. Oct 18, 2021 at 6:56 PM
    #24
    Doubleduty

    Doubleduty Life is better on the mountain

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    There are really only a few things that can cause overheating. If you check everything that has been mentioned, I'm sure you will find the culprit.
     
  25. Oct 18, 2021 at 9:19 PM
    #25
    negusm

    negusm New Member

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    Time to run an exhaust gas test on your coolant.
     
  26. Oct 18, 2021 at 11:39 PM
    #26
    suaveflooder

    suaveflooder New Member

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    Keep burping it. If that doesn’t work, focus on the head gasket. My cobra had to be burped 3-4 times before it finally stopped over heating. Start simple and work up.

    compression test is a great idea
     

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