2000 S40 Compression test shows low pressure

notalanm · Post by **notalanm** » 31 Mar 2014, 12:17

I have a 2000 S40 w/116K miles. I did a compression test a month or so ago after I had a bad engine coil that set off a misfire code for cylinder 2 (which was then replaced). I ended up replacing all spark plugs and cylinder 2's had a little bit of oil on it. I did the compression test and cylinder 1 registered at 130 (the others were 150). Added a bit of oil and cylinder 1 went up to 150. Any idea what could be causing the issue with cylinder 1? I currently don't have any misfires, but I'm wondering if this is something that could lead to big problems later or not.

I'm wondering if a partially-clogged PCV system could cause any of these issues. Otherwise, I guess I need to find a shop with an endoscope that they could put down into the cylinder to tell me for sure.

Post by **jose456891** » 01 Apr 2014, 21:19

Worn rings.

When you add oil the film creates a seal around the piston. So if the compression jumped from 130 --> 150psi, you have worn rings.

No biggie, just remember that frequent and timely oil changes reduce the stress on your engine.

difflock54 · Post by **difflock54** » 01 Apr 2014, 22:21

When the engine is running at normal hot temperature and oil is circulating properly the 20 psi discrepancy may be less than what your readings indicate cold.
I would just leave it be for now and monitor the oil consumption, with proper oil change schedule as jose456891 has stated.
Perhaps use 10w30 assuming your using 5w30 currently. (synthetic)

notalanm · Post by **notalanm** » 02 Apr 2014, 06:34

Okay, thanks for the replies. To clarify: engine was at operating temp. when I did the test and I do already use synthetic oil.