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  1. #1
    254RWHP boat anchor EVL253's Avatar
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    Default Cooling system holding pressure

    Well I'm pretty sure I have a head gasket leaking into a coolant port. Few times when I've driven this thing after putting it back together a little bit of pressure when cold just attributed it to hot temps as hasn't been bad. Bout 2hrs driving Sunday night pretty much low speed cruising with the kids for Xmas light looking. Checked fluids this morning. Oil normal. Radiator hoses rock hard. Opened rad cap & soon as the cap got halfway it blew off & sprayed coolant everywhere like it would if at full temp not stone cold.
    so guess heads have gotta come off again? Acl race head gaskets put on dry. Heads were machined block wasn't.
    11 second E85 bottle fed boat anchor

  2. #2
    Not the Kingswood! hq308's Avatar
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    Drive it again and when it cools down pull the plugs out, if there is a leak you'll have water in one or more cylinders. Get a couple of helpers, one to wind the engine over with the plugs out and a person to watch each side of the engine. If there is enough of a leak to pressurise the cooling system you'll get water shooting out one or more plug holes. Disconnect the ignition while cranking it over.

  3. #3
    254RWHP boat anchor EVL253's Avatar
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    drove it today to work. its not doing anything weird. not loosing coolant only what sprays out when you check it. only odd thing its doing but i put it down to the thermostat. when its warming up when gets around the temp for thermostat to open temp fluctuactes up & down a bit all over the place but once thermostat has opened & temp stabilised its all normal. would think if a pot was full of water it would be hard to start or would leak down past the rings into the oil.

    ill check the plugs once its cooled down but that wont be for a few days with xmas & all.
    11 second E85 bottle fed boat anchor

  4. #4
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    Retaining pressure overnight is weird, would have thought it would leak back through if it was a head gasket, usually the cylinder, an open valve or a ring gap for pressure to release to.
    Radiator cap might play a part in it, something I've never come across before anyway. Could always put a test on the cooling sysytem and cap and see if the cap releases when it should.

  5. #5
    254RWHP boat anchor EVL253's Avatar
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    could be a leak that only opens up with heat & temperature i guess. shoulda sprayed the bloody head gaskets with copper coat etc when i put em in!

    might see if we have a radiator cap tester here at work to eliminate that
    11 second E85 bottle fed boat anchor

  6. #6
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by EVL253 View Post
    .............

    might see if we have a radiator cap tester here at work to eliminate that
    .. that's my tip - the radiator cap
    as they should be the overflow type (which do NOT hold pressure)
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  7. #7
    254RWHP boat anchor EVL253's Avatar
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    well cap went on the tester. its rooted! rated at 1.3 bar pressure took over 2 bar to get it to crack open. so rounding up another one as its not stock commodore size in the right pressure rating see how that works. id hardly driven it with this radiator prior to the engine damage so hadnt come across this problem.
    will see how the new cap goes hope it fixes the problem
    11 second E85 bottle fed boat anchor

  8. #8
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    Bleed the system of air.

    Did you say you changed the radiator?

    And if so what material is it ?

  9. #9
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    2 bar, thats getting up there, at least you know there's no leaks in the rest of the cooling system then

    You could probably sell that cap on eBay to one of the burn out guys...lol

  10. #10
    254RWHP boat anchor EVL253's Avatar
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    have a filter with cap in the top hose highest point. thermostat has a bleeder hole. was filled with engine running. never had this problem before probably cause it used to use a tiny bit of coolant. new cap is a tridon 13psi unit. see what happens I guess
    11 second E85 bottle fed boat anchor

  11. #11
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    using coolant? or plain water?

  12. #12
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    Its definitely a weird one. Pressure is generated when the engine heats up. Excess pressure, in the form of coolant, is bled from the cap to the header tank. When the engine cools the pressure returns to normal then drops below & the cap allows the coolant that was ejected into the header tank to be drawn back in to the system. Where did the excess pressure come from if the engine was at the same temp. as it started at?
    I can understand the cap being faulty & holding a higher pressure before it releases but that pressure should drop as the engine cools.
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  13. #13
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    Use Demineralised water for the entire system .

  14. #14
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    Quote Originally Posted by EVL253 View Post
    have a filter with cap in the top hose highest point. thermostat has a bleeder hole. was filled with engine running. never had this problem before probably cause it used to use a tiny bit of coolant. new cap is a tridon 13psi unit. see what happens I guess
    Jack front end to 30'Rev up to 2500rpm and fill to overflowingOpen heater circuit if neededAfter t/stat opens let purge and seal with cap .Distilled water makes a huge difference

  15. #15
    254RWHP boat anchor EVL253's Avatar
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    tap water with corrosion inhibitor. don't think the radiator cap is the problem. its been sitting for 5hrs now slight bit of warmth in the hoses which are rock hard.normally at this temp be no pressure in them from experience.
    11 second E85 bottle fed boat anchor

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