chris951

Hey guys,
I did a compression test today and the engine was warm, 186,000miles, replaced turbo about 30,000miles ago after a "bolt incident." I know it's low, but at least it's consistent. I am planning on rebuilding after I get out of school. What is the wear limit for this car, I know the stock compression is around 150psi?
#1 110psi
#2 110psi
#3 110psi
#4 110psi

cpt_koolbeenz

That is really good that they are all the same! Not so good they are all 110 PSI. That is better than 3 @ 130 and one at 70! Rebuild it at your leisure - no biggie. Rod bearings will need replacing for sure at 186k, but compression test looks okay for as many miles as you have.

mark944turbo

If your starter cranks slowly for some reason that could effect the numbers quite a bit. I never trust comrpession tests for anything besides finding a hole in something (0 psi). An s2 that I bought had great, even compression, even though a cylinder was so worn down that it was slapping around noisily and visibly rocking in the bore when I took the head off. Have a leakdown test done before you decide a rebuild is necessary!

The throttle was held open during the test right?

chris951

nope, throttle was closed

Rogue_Ant

Ah, there is your low numbers... the test needs to be done with throttle open.

I also agree, do a leakdown before any drastic choices.


Rogue

chris951

thanks guys, I will redo

chris951

New compression values with throttle open are 120psi exactly on all for cylinders, how bad is that?

Perry 951

Unless you need to get into the motor, I'd run it as is. Probably a good idea to drain the intercooler since you know you have blowby.

How is your oil pressure?

chris951

oil pressure is fine

Laust Pedersen

It is very unusual (statistically improbable) that all cylinders are “identically bad”. I would do a leak-down test on at least one cylinder.

Last I measured my 186k mile engine it had 2% leak-down and 145 psi on all cylinders, so age should not necessarily be a factor.

The manual suggests that 145 psi compression is normal.

An open throttle is not critical. Cranking with a closed throttle builds at most 2 to 3 psi vacuum, which then will be subtracted from the open throttle compression number.
It also means that your 10 psi measurement difference is not easily explained.

Laust

User 41221

Its also possible that your gauge itself reads low. Where did you get your compression tester at?

Consistent is good, and 120psi is on the low end, but is an acceptable figure. Were you doing this to track down a specific problem, or were you just curious? I'd drive it and not worry about it.

Regards,

chris951

Laust,
I had a bolt sucked through the turbo a couple of years ago, so I wasn't hoping for the best compression. I'm using a cheap hesitant to say (harbor freight) piece, I justed wanted a ballpark for ***** and giggles. Man I really really really like the vacuum manifold you sent me

I soo need a test pipe and a tial,
Chris