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Registered
Join Date: Mar 2006
Location: Joliet Il
Posts: 1
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Compression test
Hi guys
Long time BMW guy but new to this list. I have heard a lot of good things about this list.... Here is my question... Can you compression test with the oil pan off? I am changing the iol pan gasket and pan and was turning the engine over by hand (with the plugs in) and heard air leaking from the cylinders from the bottom of the pistons.... Is this normal? Mike |
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03-08-2006, 08:14 PM
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Registered
Join Date: Jul 2004
Location: Brisbane, Queensland, Australia.
Posts: 80
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A delayed answer but this should enlighten you!
when you turn the engine over, by hand or otherwise you are compleating the 4 stroke pattern. Suck Squeeze Bang Blow. The air your hearing is the Squeeze part. You Notice how hard it is to turn the engine unless you do it slowly or as fast as it is prepared to let you? That is because you are compressing a cylinder full of air. The engine does this 1100 times a min at idle so there is little time for the compressed air to escape down between the Piston rings and cylinder bore, where as your doing this at about 1RPM and the only reason you can turn the motor by hand with the plugs in is because the air can escape through this extreamly tight gap. This is the hissing your hearing! Hope this helps, Luke.
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Bugger this for a joke... |
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03-25-2006, 02:27 AM
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