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Coolant leaking from...somewhere

Discussion in '6.9L IH & 7.3L IDI Diesels' started by RSchanz, Feb 25, 2021.

  1. cre1992

    cre1992 Full Access Member

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    You could always pressure test the coolant system to 10psi and see what happens. If you have leaks you will find out, and if you have a bad head gasket well... you might be pulling the glow plugs to get coolant out of the cylinders ;Poke

    Also, does one of your heater hoses run to the head on the passenger side? Could it be the hose happens to leak when it got warm? The one above / between cylinders 1 and 3.

    IMG_0961.jpg
     
  2. gnathv

    gnathv Full Access Member

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    What happens if you run it with the radiator cap off? Does it overflow?
     
  3. RSchanz

    RSchanz Full Access Member

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    Definitely not the heater hose, I checked all of the most obvious hose areas. Dry as a bone where it goes into the head.

    Without going back outside (probably still too hot anyways) I would say yes. When I started it to test if there was pressure build up with my hand while it was still cold it just started to raise in height and I just put the top on to spare myself the mess.
     
  4. gnathv

    gnathv Full Access Member

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    So you cooling system is pressurizing as soon as you start it. If you run it with the cap on does it cause the cap to vent and overflow the reservoir?
     
  5. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    The next time you have the engine running with the radiator cap on, you can try squeezing the upper radiator hose to test for excessive pressure in the cooling system. Before you start it, squeeze the hose and see how it feels. There won't be any pressure in there since you've had the cap off. If it gets difficult to squeeze the hose soon after starting the engine, you're getting pressure in the cooling system. If you are, it shouldn't take very long for the pressure to overcome the resistance of the cap and start pushing coolant into the overflow. If it is, it won't take very long before the coolant starts running out of the overflow too.
     
  6. RSchanz

    RSchanz Full Access Member

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    The overflow has gotten quite low I believe because of the leak. It definitely started to fill up after I turned the truck on.

    To bounce off of that, I wouldn't say it filled the overflow so much that it would ever overflow out of that. I drove the truck around for like 15 minutes and it didn't seem to continue to rise.
     
  7. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    It doesn't sound like you're getting compression into your cooling system. If the overflow is getting low instead of filling up, it's because the coolant is being pulled back into the radiator when the engine cools off. That is to replace the coolant that's being lost due to the leak. If you're getting compression into your cooling system, it will continue to make the coolant level "rise" and be pushed into your overflow, eventually to be pushed out of the top of the reservoir. This is how your overflow is designed to work and will work unless there's a hole in the reservoir. Even a small, slow compression leak will still have more pressure than your cooling system will ever have on it's own because of the cap/overflow design. Not to mention that you could drive around for 15 minutes and you couldn't see any noticeable change in your coolant level. If you still have doubts about this, there is a kit (probably more than one) that you can buy that lets you test for combustion gasses in your cooling system.
     
  8. RSchanz

    RSchanz Full Access Member

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    Ok so sounds like pressure test on the radiator and also combustion gas test need to be performed. Two questions:

    Could this have to do with the radiator itself? Like its clogged or something? With the OEM radiator I was leaking from only what I thought was the radiator but I guess it could have been happening elsewhere on top of that. I don't have a good comparison since that radiator was in such bad shape.

    and

    What else could be causing this pressure build up in the radiator when it's cold?
     
    Last edited: Mar 5, 2021
  9. RSchanz

    RSchanz Full Access Member

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    The combustion gas test definitely seems like a no brainer and cheap and easy. I’m not sure how I’ll be able to perform the test if fluid is overflowing out of the top of the radiator though. Can I still perform the test even if it’s overflowing?
     
  10. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    Should be no problem, the test is just looking for any bubbles that come up through the liquid. If the liquid is moving too it's not a big deal.
     
  11. RSchanz

    RSchanz Full Access Member

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    Did the pressure test on the radiator this evening. It held pressure fine at 10 and 13psi. I left it at 13 for probably slightly under 5 minutes while I checked around for leaks.

    I’m still going to do a combustion gas test but may not be able to get to it this weekend. Changed the rad cap out because I think it might be the cause. I’m really hoping it’s something stupid like that and maybe the reason the pressure never dissipates even when it’s cold is because the cap is faulty.

    I did research and found that if the head gasket was shot pressure wouldn’t be sustained in the rad when the engine is cold because the pressure would make its way back into the head gasket. Not really sure the mechanics behind this theory but sounds good to me!
    https://www.oilburners.net/threads/cooling-system-doesnt-de-pressurize.62164/
     
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  12. RSchanz

    RSchanz Full Access Member

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    As an update here:

    As stated pressure test maintained at 10psi and 13psi. Combustion gas test passed as well. Radiator cap change seems to be solving excessive pressure issue when truck is cold.

    I've noticed what I believe is a really small leak of RAD fluid from the corner of the valley pan just behind the TSTAT housing. I think this is unrelated to the original leak issue. At this point I believe the original leak was partly due to me loosening the hose clamp and RAD fluid pooling in places and being blown off by the fan along with excessive pressure from the cap not functioning properly. Fluid levels seem to be sustained but I'm going to continue to monitor it.

    :fart
     
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  13. riphip

    riphip Supporting Member Supporting Member

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    Running a 7# cap helps your radiator also.
     
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  14. RSchanz

    RSchanz Full Access Member

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    Bringing this back because the other day I noticed bubbles coming out of the hose into the overflow tank. It seemed to bubble pretty often, maybe once every 5 seconds. Still running that 16lb cap... could this have something to do with it? I'm going to replace with a lower rated cap but I'm seeing mixed reviews on running less than a 13lb cap so I'm looking for solid direction on which would be better, 13lb or 7lb?

    Can someone advise how exactly to do a radiator pressure test? I pumped it to 13PSI and watched it for about 5 minutes without it losing any noticeable pressure. Is this long enough? I'm assuming this test will test the entire engine not just the radiator for leaks right?

    I'm again going to monitor coolant levels because because I'm starting to get tired of trying to track down what might be a head gasket issue. Seems like the tests pointed not to that but then there are other things pointing to the fact that it might be an issue. I know it sounds like I should do that last case since it's more work than the other issues but I mean... Idk how the truck was taken care of and considering that this seems to be such an issue maybe just starting with a fresh head gasket is a good idea? Do studs while I'm in there?

    IMG_3334.jpg
     
  15. riphip

    riphip Supporting Member Supporting Member

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    Use 7# & 16# is way too much.
     

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