3.2 liter M30 engine

Hi. I have a 732i 1986 that has some motor problems. Diagnosis so far: Engine runs very rough

Changed all spark plugs, no change.

Checked compression on cold engine Cylinder, Comp

1, 11.5 kg (approx. 165 psi) 2, 0 kg 3, 0 kg 4, 8.5 kg (approx. 125 psi) 5, 8 kg (approx. 120 psi) 6, 10,75(approx. 155 psi)

I'm thinking the head gasket is blown as there is no compression on 2 cylinders next to each other. When I look at specifications for BMW engines it seems compression should be about 149 psi, so 2 of the cylinders are a bit hi and the working two others are a bit low, could this be due to broken piston rings? Allso I have no spec as to how much to tighten this spesific engine, the book I have lists all other engine types, but I'm hoping I can use the spec for 733i. Any thoughts on this, anyone?

Best regards

Lars

Reply to
Lars Høiby
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If the compression on the low cylinders increases when you pour some oil into the head, then the rings are the likely reason. Otherwise, the head gasket is suspect.

It is no wonder that the engine runs rough. After all two cylinders are not working at all. Jim

Reply to
Jim

Depends. Cranking compression testing doesn't tell the full story, depending on what the problem is. Hence the big variation allowed while still within spec. At higher revs those cylinders may well do some work.

Reply to
Dave Plowman (News)

..... Allso I have no spec as to how much to tighten this spesific

Thank you both for input. Time has not yet allowed me to continue, I'll be trying again this weekend, I'll keep you updated on the progress

Regards

Lars

Reply to
Lars Høiby

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