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Thread: Cooling System Issue: Is it a Burp, Head Gasket, Leak, Other Problem?

  1. #1

    Cooling System Issue: Is it a Burp, Head Gasket, Leak, Other Problem?

    I've got around 36,000 trouble-free miles on my current engine. (345 hp Ford Performance 302 crate engine.) In late June on our annual Utah Cobra Club cruise my car started puking coolant from the recovery tank. It's a typical setup; a capless radiator only having an inlet and outlet with a separate coolant recovery tank. (I'm running a Mustang radiator that has brazed cap closing the stock radiator cap fitting. It's got an aluminum CSR in-line radiator filler located on the upper radiator hose.) The overflow line runs from the CSR fitting to the bottom of the coolant recovery tank.

    The ambient temperature was over 100 when the first episode occurred while in Colorado. Although the recovery tank kept overflowing during our cruise when I stopped the engine, it was an intermittent occurrence. The engine never overheated during the 1400 mile trip. When I got home I tested the 13 psi rated radiator cap and found that it relieved pressure at around 8 psi. So I replaced the cap thinking that was my problem.

    Well, on Saturday we went for a day trip of almost 300 miles. Once again my engine performed perfectly with no overheating. However, as soon as I pulled into the garage and turned the engine off I immediately heard coolant transfer. Sure enough, coolant had transferred into the coolant recovery tank. I realize that in itself is not a problem and how it's supposed to work. However, once my engine cooled-down it did not recover any coolant from the recovery tank.

    Any thoughts on my issue? Head gasket, leak, air pocket?

    I really want to determine the cause of my problem before I start changing head gaskets.


  2. #2
    Senior Member CraigS's Avatar
    Join Date
    Feb 2011
    Manassas, Va.
    Correct type of cap so it will allow coolant to flow back into the engine? Hose from filler to overflow tank good and tightly connected at both ends? Look inside the overflow tank for any blockage of the hose connection? You have that 16# pushing the coolant out of the engine but just a slight vacuum pulling it back into the engine so it wouldn't take much to block that return.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

  3. #3
    Senior Member
    Join Date
    Feb 2011
    Summerfield, NC
    Check the CSR filler where the radiator cap's rubber seal meets the filler. Make sure you don't have any corrosion at that spot. You can get the symptom you described if the cap isn't sealing well.

    I had that happen to me at a track event...because of corrosion under the cap, pushed all the coolant into the overflow tank then out onto the track until I lost enough coolant to let the engine overheat (which warped my aluminum heads a bit). Wound up taking a tow truck ride home.

  4. #4
    I think I've got an air bubble. I borrowed a radiator pressure tester from the nearby auto parts store yesterday. I pressurized the cooling system to about 16 psi and it held pressure without any loss for 90 minutes. I even pulled all my spark plugs to see if there was any air escaping into the combustion chambers.

    Perhaps even more telling, although my coolant level was down when I removed the radiator cap from my CSR filler, the system was under vacuum until the seal was broken. So it looks like the system is working like it's supposed to. I think I just need to try and make sure that there's no air trapped in the cooling system.

  5. #5
    Senior Member AC Bill's Avatar
    Join Date
    Feb 2011
    Vancouver Island BC Canada
    Other possibility's..A soft return hose may collapse under vacuum, preventing fluid returning. Likewise if the overflow tank's vent is plugged.
    If fluid hasn't been returning on the last few outings, it could soon overfill the overflow tank, to the point it pukes fluid when more comes into it..

    After the first time it overfilled on your Colorado trip, did you add more coolant, and burp the system? Maybe air was introduced to the system on that trip.

  6. #6

    You've touched on a couple of things I've considered. On our Colorado trip I added coolant after the recovery tank puked and I think that's probably when I introduced air into the system. Also, after the Colorado trip when we returned home I simply topped-off the coolant while squeezing the upper radiator hose to purge the air bubbles. (Not a thorough burping of the system.) I've tested my recovery tank line and it seems to be OK. I have not checked my lower radiator hose, but I will. (A collapsing lower radiator hose would explain the failure to recover coolant from the recovery tank when the engine cools.)

    I was worried that I may have had a head gasket leak but I think I can rule that out since it's pulling a vacuum as it cools.

    One other thing, when we returned from Colorado I thought that the problem may have been a radiator cap issue. Although the cap was rated at 13 psi, we tested it at the auto parts store and it actually lifted/releived pressure at 8 psi, so I bought a new 13 psi cap. I thought that the new cap fixed my problem until this past weekend's episode. Air in the system and/or a collapsing lower radiator hose seem to be the main culprits now.

  7. #7
    Steve >> aka: GoDadGo GoDadGo's Avatar
    Join Date
    Feb 2015
    Slidell, Louisiana
    Blog Entries

    If you feel like you may have a head gasket issue, then you could also do the following:

    1. Check your oil for water contamination.
    2. Pull the spark plugs to see if any of the plugs look like they've been water blasted/cleaned.
    3. You can also get a head gasket testing kit which will detect exhaust fumes contaminating the cooling system.
    4. Since you have an inline water fill, you can also start the car when it is cold with the cap off and watch the water flow as the engine warms to see if it has any bubbles are being passed through the upper line to the radiator.

    Hope it isn't a head gasket, but you never know unless you check things out.

    Last edited by GoDadGo; 09-12-2017 at 02:56 PM.

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