Compression test done hot or cold?
 

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

Shawn

Shawn,

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

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

Thanks Warren

I'll do it again this week.

Shawn

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