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Thread: Z20 LET Compression test

  
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    Z20 LET Compression test

    Hi all,

    after having changed my turbo and still having oil trouble, i did a compression test.
    does anyone know what readings i should have got?
    here is what i got

    1. 60PSI
    2. 160PSI
    3. 130PSI
    4. 60PSI

    wierd!
    John L

    MK4 GSI

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    That does'nt sound good. They should all be similar.

    Time for further investigation

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    All 4 pistons should give a fairly close reading. As Coo says those dont look too good

    What were you compression testing for anyways ??? - out of interest

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    Quote Originally Posted by LordNikon
    All 4 pistons should give a fairly close reading. As Coo says those dont look too good

    What were you compression testing for anyways ??? - out of interest
    I was told to try a compression test because i have been having excessive oil out of cam shaft breather. spits it out when just using starter without letting engine kick in.

    Very worried now!
    John L

    MK4 GSI

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    you sure thats right mate, i had mine done and all of them read near 130 i think
    YOUR FRIENDLY WINDSCREEN MAN

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    They should all read around 130 Mark, yours are quite right. Deviance either way is fine, but the readings above are all over the shop.

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    i held starter motor on for about 5 seconds per test.

    could this be a head gasket issue?
    John L

    MK4 GSI

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    Put a spoonfull of oil in the cylinders via the spark plug holes, then do the compression test again If the compression increases then the piston rings are shot. If not then possible head gasket, but is there no signs of this in the oil?

    hth mate

    Jim
    Z20LET Hybrid Vectra Running 347BHP / 386Lb/Ft


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    Hi jimbo,

    No sign of headgasket leakage in oil. the oil does not stay in the engine long enough tho!
    goes through about 1 litre of oil every 50 miles.

    would one piston ring being shot effect the other cylinders?

    will be totally gutted if 3 set have gone on such a low mileage engine, its reached 10300 now.
    John L

    MK4 GSI

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    It is unlikely (or should that be unlucky) that the two end cylinders had low compression. If this result is correct, this means you have two seperate problems.

    I would say it is more likely a bad reading. Try doing it again with a drop of oil as suggested above.
    8 Astras in a row! Can Anyone Beat That?
    Star Silver Astra Sporthatch SRi XP 1.9 CDTi (150PS)
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