Compression test done hot or cold?

[davis911s]

I always thought these were done on a cold engine but now I am reading the engine should be warm. Which is best?

Shawn

[Early_S_Man]

Shawn,

Engine warmed up to normal operating temperature, all of the spark plugs removed, throttle wide open, and fully charged battery!

------------------
Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[davis911s]

Thanks Warren

I'll do it again this week.

Shawn

[jbailey930]

I'd also disconnect the fuel pump relay, coil and unplug CDI....

How about leak down procedure? I just did this on my 930 to see if I had a "broken head stud" as my mechanic indicated from a test drive:

1. warm engine to normal operating temp 180 ish
2. remove all plugs (and intercooler in my case).
3. rotate to TDC at #1 and check #1 cylinder using Summit gauge(supplied by friend) at 100psi.
4. rotate through each cylinder advancing to TDC for each check.

Using this process I saw no less than 5lbs difference in each cylinder. When I did not properly advance the engine I saw(and heard air escaping) big time drop in pressure. I felt comfortable with the results although I may have to remove valve covers just to be sure and torque the bolts.
Best
John
79 930
87 951