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Compression Test advice please.

Discussion in 'A3/S3 Forum (8L Chassis)' started by Shy19s, Jul 10, 2008.

  1. Shy19s
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    Shy19s Oil running through my veins.

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    Hi guys, did a compression test, Readings came back 180-170-170-160 psi.

    Cranked it over 4 times the first time, then did another test again for 10 seconds on each chamber and got the same reading..

    Not on an A3/S3 but any advice as far as compression tests go does this sound like the block might be warped? Already changed the Headgasket and had the head skimmed, but its still loosing water.

    Im thinking water pump or a water leak from somewhere else but still white smoke coming from the exhaust when it gets on boost. No water left in the rad after you blitz it for a couple of miles and over heats.

    I realise the compression should be alot lower but its N/a engine that has been turbo charged, Im guessing its fine as its over 150psi but shouldnt it be more consistant? or does this little decrease along the block normal?

    Also took all the plugs out and cranked it over and no water was spurting up through the plug hole, obviously the injectors were unplugged throughout the test also.

    Thinking it could be liners but no evidence yet, any other tests we could do?

    It has left me and a friend quite baffled..

    Any advice welcome, Thanks in advance.
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  2. Shy19s
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    Shy19s Oil running through my veins.

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    Nobody done a compression test before?
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  3. S£
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    S£ Member

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    Funny you should say that...


    I done a compression test on my mouse today, F**king thing kept playing up so thought i would see how far i could compress it into the table!!
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  4. ALPINE
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    ALPINE Yes its diesel, now cry u lost

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    was it messy when the mouse exploded??

    :undwech:

    sorry lame i know.... just pictured you, a mouse and a bike pump!
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  5. HTC
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    HTC Active Member

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    You are within spec I'd say. I don't like to see more than about 14psi difference across the cylinders.

    You are better off going for a leak down test. Not all garages seem to offer this, but its basically a tool similar to a compression tester but with two gauges. You attach it to the spark plug hole and an air line. Set the engine at TDC for that cylinder and then set the gauges so they are level and use the same pressure for all cylinders.

    You listen to parts of the engine:

    Remove the oil filler cap and listen for hissing, this would indicate a piston ring leak.
    Listen to the exhaust for hissing, this would indicate an exhaust valve leak.
    Listen to the intake, indicating an inlet valve leak.

    If inconclusive, then it's probably the head gasket.
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  6. h100vw
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    h100vw Member

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    You might see air bubbles in the coolant or maybe the level change if air leaks into the water system.

    There is also a dye that detects combustions products in the water.

    Gavin
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  7. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    i would get one of those dye kits and test it with that, it checks for combustion in the coolant( or something like that)

    Although the symptoms you describe certainly point towards a HG or head etc.

    is it a wet lined engine? Did you get the head pressure tested? as it could be cracked internaly
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  8. fingermouse
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    fingermouse thats me

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    funny you should mention that my mate was on about those as hed seen one used on a sky doc channel about some garage somewhere doing a fly on the wall thing.
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  9. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    About £30 delivered from ebay, they even sell spare fluid stuff too
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  10. Shy19s
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    Shy19s Oil running through my veins.

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    Thanks for all the replies lads, havnt pressure tested it yet, and will look into the dye, and all the other suggestions and report back.

    Thanks again.
    #10

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