911 SC Cylinder leak down test questions
 

At 110,033 miles in March of 2016, my mechanic performed a cylinder leak down test on my 78, 911SC.


The results were:

#1=6% #2=7% #3=6%
#4=9%R #5=6% #6 = 6%

I'll assume these numbers indicate the engine is likely okay for another 20K-30K miles
or more without a top end rebuild? What does the R after #4=9% mean?

Have added 3 K miles in 2 years and all seems good. Looking for advice on how this information might support the sale of the car.

Well
Leak down tests must be done correctly on Porsche engines and I find a big variation on the numbers. One mechanic tried to tell me my engine needed a top end and it had 8,000 miles on a rebuild. I latter told him that is was just rebuilt ...but he tried to say it was leaking from a bad piston ring in 2 cylinders...I tested it and got good numbers

The car runs great, go figure, I am told the % of the leak down per cylinder should all be close together and yours seem to be wearing the same...

A leak down test can be an indication of where a problem is, if one is suspected.

I am guessing that the R might mean rings. The mechanic should indicate where the leakage was occurring, if the number was high.

If the motor is not using oil or fouling plugs I would not worry too much. A leakdown will not show worn valve guides.

Have it done again by another mechanic after a while and see how it compares if you are concerned.

If a compression test was done and one cylinder was low, a leakdown could indicate where the problem lies. IE, rings or valves.

FWIW, I did a leakdown on a motor I just sold. I got 6-7% on all but #5 which was about 10% with leakage through the intake valve. Later the buyer did his own test and he was getting 2-4 % on all cylinders except #2 which was 12% through the exhaust valve. I pulled the valve cover and banged on the rocker arm and it went up to 6%. Probably both issues due to carbon flakes on the valves.

If I was you, I would wait until you are selling and have the buyer do a test if he wants.