low compression on all cylinders

[yoni]

1991 325ix -

The compression on all 6 cylinders is about 100 psi -

This seems really low to me - what should I be checking for issues ?

Head gasket..?

TIA

[Devil Inc]

Possible, has the car been setting for a long time?

[yoni]

Not really - i drive it daily...

Is the low compression a problem ?

I'm losing a lot of power, aren't i..

[KenC]

What are M20s supposed to be at? You're checking it warm, right?

[yoni]

Yes - I'm going to run another compression test, to make sure.

I think my Bentley said something like 150psi

[KenC]

Rings are beat then.

[yoni]

expensive job?

[KenC]

The rings themselves aren't that expensive. Would probably take you a whole day to do if you knew what you were doing. Probably need to have the bores honed though.

[txtorquemade]

Im no expert but I believe that if compession is reduced by 20% or less your ok. If its more around 50% you need a rebuild.

Is that right??? Anyone?

[bimmerboy12]

Do a leak down test to determine if it is rings or valves. Or, put a squirt of 10W30 in each cylinder before you test it to see if the the compression goes up. if it does, the oil is temporarily sealing the faulty rings and you know you need new rings. if compression is unchanged, you have a valve issue (seats, buildup, etc)

[Huck]

Oh, and by the way, make sure your compression gauge is a good one!! I recently rebuilt a dirt bike engine due to a faulty compression gauge. DA!!!
A leak down test is much more accurate (you can buy the tool at Harbor lFreight for around $35.)
Do the oil squirt down the plug hole on just one cylinder and retest. In my experience, having every cylinder at the same compression and that being a 30% drop from stock ideal--well I am a bit suspect as usually you get a different reading by 5-20 lbs per cylinder.