compression test results - seem high?

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s13b
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Sat Jun 29, 2013 6:59 pm

Hi,
Just done a comp test on my warm m20b25, the results were the same across all cylinders but seem quite high compared to what I have read elsewhere on t'interweb.

14 bar + on all cylinders (>200 PSI)

Thanks in advance
Speedtouch
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Sat Jun 29, 2013 7:12 pm

They do indeed sound very high; normal pressures are around 175-190 psi.

Are you sure the gauge is calibrated, and which engine block do you have - 25 6E or 25 6K?
///M aurice
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s13b
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Sat Jun 29, 2013 7:32 pm

gauge is brand new and will confirm block shortly.
macas
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Sat Jun 29, 2013 7:49 pm

How can you have "too" much compression?,I thought more the better?

That's a genuine question not a smart Alec remark btw :D
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s13b
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Sat Jun 29, 2013 7:57 pm

well i have some quite bad oil leakage issues so high compression may be responsible.

Basically enough pressure to blow the filler cap off! Both oil breathers are clear so not sure where, why or how it is leaking oil but if I drive over 2k rpm it proper spooges oil from somewhere around the back of the block. Comp test was first point of call.
scjimbo
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Sat Jun 29, 2013 8:04 pm

That's got nothing to do with compression. The filler cap blowing off is crank case pressure. It's interesting that you have too much compression as well as ccp.
scjimbo
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Sat Jun 29, 2013 8:05 pm

I know this sounds stupid but how much oil is in the engine?
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s13b
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Sat Jun 29, 2013 8:15 pm

how much oil? Well the dip stick is a good level and i put in the "correct" amount...
scjimbo
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Sat Jun 29, 2013 8:38 pm

Only reason I ask is because overfill could cause a high amount of crank case pressure. Have you tried running the engine with the filler cap off?
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s13b
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Sun Jun 30, 2013 1:26 pm

Engine runs fine and oil goes everywhere its supposed to. None of the pathways are blocked and new oil is still nice and golden.
Only other thing I have changed is I rotated the oil filter housing to allow for tubular manifold, and removed the oil cooler. From research I understood that both of these are completely fine to do... Unless I maybe have restricted the oil channel into the filter housing somehow
Speedtouch
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Sun Jun 30, 2013 1:39 pm

What grade of engine oil did you use? It may be worth trying a thicker one - 20W50 was used back in the day, when these engines first came out.

Lighter grade modern stuff may be too thin and be the cause of the leakage on an older engine.
///M aurice
ECU Upgrade EPROM Chips, £40 posted within the UK. Note these are not Zone chips.
viewtopic.php?f=6&t=279421
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s13b
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Sun Jun 30, 2013 1:44 pm

Im on 10w40 semi-synth at the moment and that is what I have used since I owned the car.
I replaced the headgasket recently and did a complete top end rebuild and problems have only started since then.
I think oil is leaking from the rear crank seal area, but still no real clue as to the cause.
Speedtouch
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Sun Jun 30, 2013 1:48 pm

Check the oil pressure relief valve is functioning properly.

http://e30.bmwdiy.info/oil-leak/
///M aurice
ECU Upgrade EPROM Chips, £40 posted within the UK. Note these are not Zone chips.
viewtopic.php?f=6&t=279421
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