Low Compression?

[honclfibr]

Measured my engine compression today, just for kicks really, planning on doing some work to the car and I wanted to make sure it was in good condition first.

Wasn't happy with the results, though. From left to right (towards the timing belt) I got the following: 165, 170, 130, 130.

First two look good, last two, not so good. I'm going to go squirt some oil down those last two to rule out valves, anything else I should check? Any idea what this could be?

 

[honclfibr]

Update: After pouring a bit of 5W-30 in each cylinder, this is what I get, left to right: 250, 210, 220, 240.

This is strange, without the oil, my rightmost cylinders are 30psi low. With the oil, my center cylinders are 30psi low. What gives?

One thing I didn't do was warm the carm up before I did the compression test, I just rolled it into the garage, so it wasn't running for more than 15 seconds. Would this be a problem?

 

[oldman]

Looks like the second cylnder is the only normal one. If you have done the test correctly, ie car temp and amount of oil used, then the other 3 probably have bad rings.

 

[honclfibr]

Looks like the second cylnder is the only normal one. If you have done the test correctly, ie car temp and amount of oil used, then the other 3 probably have bad rings.

Thanks, I'll check that out. Two things I forgot to do was warm the car up, and hold the throttle WO while cranking. I'm going to repeat the test with both and see if it improves.

I really didn't expect to have a problem here, I have 50k on this motor, stock turbo, oil changed every 3k with mobil 1. The engine should be damn near perfect.

 

[oldman]

Make sure you don't use too much oil during the wet test, less than capfull (not the huge Mobile caps) is enough.

 

[honclfibr]

Make sure you don't use too much oil during the wet test, less than capfull (not the huge Mobile caps) is enough.

Thanks, yeah I only used about a teaspoon for each cylinder, still smoked like hell when I started it up though...

So after the wet test I ran the car for a few minutes, then took it out and gave it a little boost to clear out all the oil. Came back with a hot engine and did the test again, with my foot at WOT this time.

Left to Right: 170, 175, 155, 155. So there's still a problem here, but not as severe as I expected. Still, this was *not* what I expected from an engine with 50k well cared for miles on it. Any ideas as to what could have caused this? Or where to go from here?

 

[oldman]

The last two might have minor ring leak but those numbers looks fine. Warm the car up again and do the wet test again see if the last two changes drastically.

 

[honclfibr]

Did the wet test again, this time it was 220, 215, 210, 225. One thing, I was a bit more careful about pouring the same amount of oil down each cylinder this time.

 

[oldman]

Dude stop bitching, you're fine.

 

[honclfibr]

Dude stop bitching, you're fine.

Hehe, allright. Thanks for your help. I just get a bit paranoid sometimes, y'know? But the damn thing is going in for a clutch / flywheel / timing belt / waterpump in about 3k miles and that's a pretty penny to spend on a dying motor, just wanted to make sure things were kosher. Thanks again