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Thread: Radiator Cap - 345

  1. #1
    Join Date
    Jun 2009
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    Default Radiator Cap - 345

    I managed to fix some electrical gremlins this evening and got my truck running again but when it did, water started pouring out of the radiator escape line. The engine had only been running for 30-45 seconds so it wasn't hot and I haven't aded water anytime soon so this really confused me. I drew a little more water out to make sure it wasn't just full and same thing happened.

    I then went to the local auto parts store and got what I think is a matching Slant radiator cap (16 psi) that fit well. Took the truck for a spin and everything seemed to be just fine but about 10 minutes later the same thing happened again.

    Am I using the wrong type of radiator cap and why would this start happening now when I haven't done anything to the radiator?

    Any help or advice would be appreciated...

  2. #2
    Join Date
    Feb 2009
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    I hate to be the bearer of bad tidings, but it sounds like you have a blown head gasket. Those bubbles in the coolant are exhaust.

    How many miles on the engine?
    Allan E.
    Curmudgeon Extraordinaire
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  3. #3
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    Jun 2009
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    Dang. I hope that's not it.

    The odometer reads 89k miles but it's a '73 so it might have flipped over at some point.

    I don't have any major oil leaks, excessive exhaust smoke or loss of power. I guess I'll check the oil tomorrow. Anything else I can check?

    Dang. This just ruined my night..

  4. #4
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    Jun 2009
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    Curiosity killed the cat or at least made him smell like exhaust before bed....

    I watched the coolant fluid as the engine heated up and I didn't see any bubbles at first. I revved the engine a bit and as the fluid rose and dropped some froth developed but it didn't really look like bubbles forming. Instead, it appeared like the coolant was splashing around and creating that froth.

    I'm not sure I could diagnose a blown head gasket if I had to so I've taken two videos. The first is of the coolant when the engine is cool. No bubbles.

    http://www.youtube.com/watch?v=hhZhQbxnY3k

    The second is of the coolant after the engine heated up. I don't see bubbles other than those created by the flow of the water. It might be my blind faith and hope that the head gasket is ok though...

    http://www.youtube.com/watch?v=kcI5RAuZPKA

    Oil looked good. I could probably change it this weekend just for fun but I'd rather not if I didn't have to. Anything else for me to test?

    I know the coolant looks horrible and needs a change. I haven't flushed it in over two years. Anyone care to diagnose via the videos?

  5. #5
    Join Date
    Jun 2009
    Location
    Little Rock
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    Did you add more coolant or water after all your old stuff ran out? Was there any white goo around or inside your original radiator cap when you first pulled it off? Check your oil and look for signs of a whitish gooey residue. From the video it did look like you had bubbles when you gave it gas, but hard to see as the lighting was kinda low.

  6. #6
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    Remove the thermostat. Put the housing back on without it.
    Fill up the system with water. Get all the air out of it. Be thorough. Leaving the t-stat out will make that MUCH easier.
    Run the engine. See how it acts. Leave the radiator cap off. It should not overheat or blow bubbles at you. Let it run for a while.

    Film at 11...
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  7. #7

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    16 psi is a little too much pressure IMO. I wouldn't go over 13, 7 if I can get away with it.

    But if it's blowing past the 16lb cap and it's not getting hot enough to expand the water then you have excess pressure in the cooling system from a bad head gasket, cracked head etc.

  8. #8
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    Feb 2009
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    Paso Robles, Ca
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    What does your oil look like? Milky? If you remove the theromstat, it will actually run hotter as the water does not have time to cool down in the raditor before cycles through again.

  9. #9
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    Quote Originally Posted by rbelflower View Post
    What does your oil look like? Milky? If you remove the theromstat, it will actually run hotter as the water does not have time to cool down in the raditor before cycles through again.
    That's true over the course of several minutes or more on a hot day at freeway speeds, but for the purpose of this test, it would be a safer way to make sure the system is purged of air. One of the things that can happen is that the system doesn't warm up very fast. It can take several minutes longer without the t-stat blocking the coolant when the engine is cold.

    Also, try running a scout 80 with no t-stat, even in summer. None of the ones I have ever owned would even warm up. Used to drive me nuts.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  10. #10
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    Feb 2009
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    Paso Robles, Ca
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    Allan,
    I figured that you were aware of the runnign hotter since you post was very detailed. I was just trying to make sure that he was aware that it would run hotter if he left it that way... I was thinking the say thing about the 'stat' being blocked.

    I did not know about the 80/800's and their lack of heating issues.. thanks for the note. I have a friend that was thinking of getting an 80/800.

    When I got my Scout, I did not have a fan shroud and a slipping tranny... needless to say, I had a really big overheating issues when going up hills slow. At the time, he (my friend) had a Samari and I about pushed him up the hills or if I was leading, I had to stop and wait... a lot.

    Thanks again for the notes.
    Regards,
    Rob

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