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  1. #1
    735i Turbo
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    Help! Blowing Coolant During High RPMS

    I've just completely re-built my engine. Whenever I get on it for over 10 seconds my engine temp maxes out hot and blows coolant out of the cap. I've replaced the cap, and the thermostat. I had a 75 but put in a 80. Could there be air in the system if so how should I bleed? Kurt


  2. #2
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    Re: Help! Blowing Coolant During High RPMS

    Like my post below, thats pretty much the same thing mine did. Im thinking now thats just what happens with turbo cars. The turbo gets so hot, when you get on your car temps in the area of 1500-2000 degress. In Corky bells maximum boost it says never completely floor a turbo car for more then 15 seconds, thats probably the reason why because of the amount of heat it creates.

  3. #3
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    Re: Help! Blowing Coolant During High RPMS

    First off, how is your radiator? Seems foolish to spend money on rebuilding an engine and not making sure the radiator is up to spec. Is the condensor in good shape, not blocking airflow?
    Showing my ignorance of the 7-series, I'm assuming that there is an electric fan in front of the condensor (either temp or A/C controlled), perhaps a boost triggered switch to turn it on would help.


  4. #4
    Kris
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    Thats called blown stuff

    you've got a blown headgasket.. craked head or cracked block... your blowing all your compression out of it... time to take your engine back apart :) unless your boosting more than 15 lbs of boost... no turbo isn't going to pressurized the cooling system more than your radiator cap can handle... the rest is wishfull thinking

  5. #5
    Pat P
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    process of elimination...........

    1. thermostat check....(install new one...even new ones malfunction)
    2. re-bleed the system....
    3.pressure test the system...low pressure....(blown head gasket/bad head)
    4. check top radiator hose (if very stiff headgasket/head)

    how is the temp during normal driving?


  6. #6
    Pat P
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    also test water pump


  7. #7
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    Re: process of elimination...........

    When it happened to my car, that was the only time its gotten hot. I've gotten on my car since, and hasn't got hot at all. my coolant level doesn't drop any lower. During normal driving since my car has ran at perfectly normal temps, same as before.

  8. #8
    Pat P
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    Then your gasket..is compromised .......(more)

    Well I will say that if the problem only exist when you boost and the water is pushing, then your HG is damaged in some way or form around a water jacket......

    I have had this problem with my 89 325ic a few years back we had put on a new HG and the head pinched a water jacket while puttin on the head.....Then we bought a new head gasket (AGAIN) and next time it was ok.


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    why would you have to limit it at 15 secs if you

    can keep your egt's stable (or relatively so)? I guess that's a lot of heat in the engine bay - I know Pat's cars run around 1400 egt - then again 15 seconds floored in one of his cars... well... let's just say you never have a reason to be going that fast... LOL
    Kai Xing
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    86 645CSi 5-speed

    "Either you stand for something, or you fall for everything.".

    Engine Removal Site
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