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Radiator Coolant Overflow?

Discussion in 'Early CJ5 and CJ6 Tech' started by lorne, Dec 10, 2005.

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  1. Dec 10, 2005
    lorne

    lorne Ummm...

    Fremont, CA
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    Sep 23, 2002
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    Hi guys,

    Just fired up the Jeep today and ran it in the driveway for about 5-10 minutes. Noticed coolant streaming out of the overflow tube onto the ground.

    Any help on what would cause this? Blocked thermostat? Bad cap?

    Thanks...

    lj
     
    lorne, Dec 10, 2005
    #1
  2. Dec 10, 2005
    $ sink

    $ sink Gazillians of posts

    Virginia Bch
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    first guess, cap not on tight, second would be bad cap.
     
    $ sink, Dec 10, 2005
    #2
  3. Dec 10, 2005
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    First question though is did it overheat? Did it leak after running and warming up?
     
    Glenn, Dec 10, 2005
    #3
  4. Dec 10, 2005
    lorne

    lorne Ummm...

    Fremont, CA
    Joined:
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    Maybe, I only ran it about 5-10 minutes before it started to leak...it definitely came from the tube that comes off the top of the radiator filler neck.

    lj
     
    lorne, Dec 10, 2005
    #4
  5. Dec 10, 2005
    Patrick

    Patrick Super Moderator Staff Member

    Los Alamos, NM
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    That is an open system... In other words, no overflow reservoir. The radiater will not stay full. When the coolant warms up to operating temperature, it expands about 7% . If there is no overflow tank, it will push out coolant until the system is still full when hot, but when it cools down, the coolant level will be below the neck on the radiater... Clear as mud?
     
    Patrick, Dec 10, 2005
    #5
  6. Dec 10, 2005
    lorne

    lorne Ummm...

    Fremont, CA
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    I understand what you're saying Patrick, but I haven't added any coolant and it hasn't done this before...which is why I'm concerned...

    lj
     
    lorne, Dec 10, 2005
    #6
  7. Dec 10, 2005
    Patrick

    Patrick Super Moderator Staff Member

    Los Alamos, NM
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    My Jeep will burble (technical term:D) if I shut it off *just* as the thermostat is opening...
     
    Patrick, Dec 10, 2005
    #7
  8. Dec 10, 2005
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    If the coolant is at the proper level in the radiator when it's cold then it shouldn't overflow even when it's completely warmed up. Stuck thermostat gets my vote in this case.
     
    Glenn, Dec 10, 2005
    #8
  9. Dec 10, 2005
    Patrick

    Patrick Super Moderator Staff Member

    Los Alamos, NM
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    I agree.... The radiator will not be full when checked cold...
     
    Patrick, Dec 10, 2005
    #9
  10. Dec 11, 2005
    springerfever

    springerfever Member

    suwanee, ga
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    Can't say whats causing it, but I think Patrick is right about the expansion. Whenever I topped mine off when cold, drove her for a while and then shut'r down, I would have overflow on my garage floor.

    After installing a $8.00 NAPA overflow tank and routing the hose to the bottom, no overflow. Now its a closed system and the radiator will either siphon or expel excess coolant into the tank. This also eliminates an air bubbles in the system...well worth the cheap upgrade.
     
    springerfever, Dec 11, 2005
    #10
  11. Dec 11, 2005
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    If you mean you topped yours off when cold by filling the radiator to the top that is wrong. With no overflow system the level when cold should be approximately 2" below the neck of the radiator. This allows room for expansion. If it overflows when shut off something is wrong.
     
    Glenn, Dec 11, 2005
    #11
  12. Dec 11, 2005
    springerfever

    springerfever Member

    suwanee, ga
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    yeah......I see your point. If SOP is to fill with the two inches remaining, this allows for the expansion.
     
    springerfever, Dec 11, 2005
    #12
  13. Dec 11, 2005
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Note I said approximate, 1.5 to 2 inches should work fine.
     
    Glenn, Dec 11, 2005
    #13
  14. Dec 11, 2005
    lorne

    lorne Ummm...

    Fremont, CA
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    I replaced the radiator cap today and started it up again. It was in the exact same spot I had it yesterday (didn't move it) so as to keep all conditions the same. Ran it for about the same lenght of time and no leak! :) The old cap was very loose so for now I'm chalking this up to a bad cap - thanks for all the advice.

    By the way, coolant is about 1" above the fins - maybe the same distance below the top of the neck.

    lj
     
    lorne, Dec 11, 2005
    #14
  15. Dec 11, 2005
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Good deal, probably cap was the cause. Pretty mean though, not telling us the cap was loose, as in weak. R)
     
    Glenn, Dec 11, 2005
    #15
  16. Dec 12, 2005
    dohc281

    dohc281 It is what it is.

    Laurel Springs, N.J.
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    Mine started overflowing out the overflow tube recently.I mean overflowing, not dribbling. The radiator cap is only a few months old and the thermostat is the same age. I took the radiator out and had it rodded. Reinstalled it and no change. I took the thermostat out and will replace it with a 160; it has a 180 in it now. Hopefully this is the problem.
     
    dohc281, Dec 12, 2005
    #16
  17. Dec 12, 2005
    lorne

    lorne Ummm...

    Fremont, CA
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    That was a test to see how good you guys were at diagnosing problems! :D

    lj
     
    lorne, Dec 12, 2005
    #17
  18. Dec 12, 2005
    dohc281

    dohc281 It is what it is.

    Laurel Springs, N.J.
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    I got a 160 thermostat today and installed it. I let the engine run for about 5 minutes and then took the Jeep for a short ride in my development and when I came back home I opened the hood and everything was dry. In the morning I'll check the radiator and see where the coolant level is. Before I put the thermostat in I drilled 2 1/8" inch holes in it. I hope this solves the puking problem.
     
    dohc281, Dec 12, 2005
    #18
  19. Dec 12, 2005
    Patrick

    Patrick Super Moderator Staff Member

    Los Alamos, NM
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    :shock: 160*??? I'm surprised you actually found a 160* thermostat... That is too cold. An internal combustion engine needs to be up to be up in temperature for the combustion process to be efficient..... My dauntless runs the best at about 200* or so......
     
    Patrick, Dec 12, 2005
    #19
  20. Dec 13, 2005
    dohc281

    dohc281 It is what it is.

    Laurel Springs, N.J.
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    My thinking was that the 180 I had was not opening completely until well over 180. I figure that it will still obtain the correct operating temp just that it might take a little longer to get there. I bought it at FLAPS.
     
    dohc281, Dec 13, 2005
    #20
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