Low compression

[rattlsnak]

Hey, I'm a early 911 guy but a friend with a '99 boxster was having a problem with running rough and a compression test showed all three cylinders on the right bank ( passenger side ) were @ 30 lbs. I pulled the motor out today and am getting ready to do a leak down check but is there any common problems or anything in particular I should look for first? I was thinking head gasket maybe, but all three cylinders is unusual. I pulled the valve cover off and everything looks fine. All the fluids were fine with no coolant in the oil. Any ideas?

Thanks.

[Travis84]

Camshafts still in time? Set it at tdc and pull the green caps, the notches in the cams should be parallel with the head. sounds like it jumped a tooth, common of a ims bearing that is very loose.

[rattlsnak]

thanks, i will check that. the chain on that side does appear to be tight though.

[Travis84]

the tensioner still works so it will be, but if the ims can flop around when its running...

[Dave2001S]

Hi, just jumping here, I am curious about the leak down test and what might be considered 'good' numbers' for results? I am about to have that done on my 2001 S 986, and I'd like to know what to look for in terms of good vs bad, or acceptable vs not (if that makes any sense). Thanks!

[Travis84]

main thing is consistency. anything less than 10% is good, but you want all cylinders pretty close to same. Any reason your having it done? cylinder sealing is not a big problem on these motors...

[rattlsnak]

haven't got around to doing anything yet. just sitting in the corner of the shop waiting.. lol..
All I know is the right side compression levels on all three cylinders were about 30 PSI..