: Compression numbers for the North*



fristim
03-27-06, 05:57 PM
I own a 98 concours with 168000 on th odo and am about to do a compression check on all the cyls. Just wondering what are the numbers suppose to be for the PSI on a healthy motor. Im also doing a wet compression check and was wondering if that would be ok to do on this motor, I really dont wanna mess up my o2 sensors or any thing. Any feed back would be greatly appreciated as I surely dont wanna screw any thing up. Thanks a lot and remember: DRIVE IT LIKE YOU STOLE IT!

Ranger
03-27-06, 06:32 PM
I think the important thing on a compression check is that all cylinders are within 10% (if memory serves me correctly) of each other. Actual psi is not important but I would guess they'd be in the 150-175 range?

eldorado1
03-27-06, 07:31 PM
I tested mine about a month ago, but forgot the numbers... sorry

parts68
03-27-06, 07:36 PM
just did a 95 rora with 160K. dealer said it had 2 dead cylinders.
lowest was 185,highest was 225.
I decarbonized it and the highest went down to 205 which was much better.
still trying to figure out what cylinder was dead(not).Runs smooth as silk after new plugs.

Zorb750
03-28-06, 08:36 AM
Should be around 180.

dkozloski
03-28-06, 12:32 PM
Make sure you do the compression testing with the throttle propped open wide and a good hot battery. Both common reasons for wierd results.

parts68
03-28-06, 08:32 PM
and a warmed up engine ,all plugs removed.
Zorb I think 180 is low,see my results with a 95 and 160K on clock.
FSM says 140-170 but thats terribly low so it cant be right.

Raze
03-29-06, 03:00 PM
A leak down test is more conclusive, search around the procedure has been documented a number of times.

The Factory Service Manual for my 98 ETC has the list at 140-170psi at cranking speed with throttle open

Eldobroken
04-03-06, 06:12 AM
I think the important thing on a compression check is that all cylinders are within 10% (if memory serves me correctly) of each other. Actual psi is not important but I would guess they'd be in the 150-175 range?
Exactly what I would have said. As long as there all close your ok.

Zorb750
04-06-06, 09:55 PM
No. As long as they are all close and all high enough you are ok.

auroradude
04-07-06, 09:30 AM
I'll be doing 1 on mine before i get a new car. I did the Auto-RX treatment twice before, and let me tell you it dfeintaly runs better after that. Im sure that cleaned up the compression somewhat, and the filler hole looks worse on the before pictures.