The car that I am looking('91 964 w/ 40K) at had a compression and leakdown done.

Compression numbers were good at 205-210 across the board.

However the leakdowns came in at 20-26%, concerning for me who knows little. The car has been sitting for the past 6 months(driver was unable to drive due to injuries), could this explain this. Report didn't suggest the source of the leak and I plan to call the mechanic tomorrow to ask more about it.

 

20-26% in all cylinders?

 

That is correct - all were between 20-26%.

Someone on PelicanParts suggested Techron, 10gal of high octane and a hard run suspecting carbon deposits.

Any thoughts?

 

What I find odd is the VERY high compression numbers and the very bad leakdown numbers. Further for them all to be roughly the same with very little variance (shows consistency), I would suspect that there is some error in the test which could be on the user end (engine temp, valves all closes properly, etc) or error on the motor end for sitting so long.

Do you have the luxury of running a tank of fuel with some varied high RPM driving? I know you said you were looking at the car but if the owner would allow that then cool. I just have a hard time understanding how only 6 months could produce these results.

Who did the compression and leakdown test? What did they suggest?

 

[QUOTE=LVDell;5906007]What I find odd is the VERY high compression numbers and the very bad leakdown numbers. Further for them all to be roughly the same with very little variance (shows consistency), I would suspect that there is some error in the test which could be on the user end (engine temp, valves all closes properly, etc) or error on the motor end for sitting so long.

+1. Are you sure the Tech knows his business? Very unlikely that leakdown numbers would be THAT high, and consistent on all cylinders with those compression numbers.

 

Porsche dealer did the compression & leakdown

They felt that the numbers were OK. I had a long discussion with the mechanic this morning who was convinced that the motor is good.

 

I find it VERY suspect that a mechanic would deem a motor "good" (subjective) with leakdown numbers all above 20%!!!

 

The gauge that was used could be way out of calibration .
If I were you , I think I would try another shop to verify the results or disprove the results .
If you go this route , don't tell the 2nd shop about the first set of results .

 

One can expect those leakdown numbers on an engine out of Detroit but on this engine single digit values are exceptable and below 5% on a good engine.

Bill
90C2

 

+1.

There is some shred of truth to the "has not been run in awhile" argument, however, what I have seen is more like 8-12% dropping to 2-8% and calling it a victory. Leaks over 20% are just plain too high.

With a 40k mile motor I would continue testing. Good luck.

 

Does not make any sense. Compression WAY high, and leakdown very bad. Did this shop give you a clue where the leakdown was occuring (intake or exhaust valve or into the crankcase through the rings?)? If not, then find a shop that knows what they are doing.

 

+10 to all of the above.

 

Echoing same thoughts as above: a pile of carbon on each piston would pretty much have to be present in each cyl. for compression that abnormally high, plus that same crud causing valve leakage - but not that consistently across every jug.
<<< Humphrey says, "Whoever is doing the test is screwing the pooch".