low compression & low leakdown test results on '90 c2?
 

Hi all,

I'm considering the purchase of a '90 c2 cab w/ ~90k miles on it. The car looks good in pictures, etc. and the maintenance history I have gives me the feeling that the car was well taken care of. I'm in the process of getting a PPI done on the car now and the compression & leakdown test results don't make any sense to me.

I spoke to the mechanic today who said he had finished testing 3 cylinders. Compression on each was 125PSI and leakdown was zero on 2 cylinders and very small on the other (<<5%). The compression seems VERY low to me based on the compression ratio of the engine and typical results I have found through searching this site (among others). The car is not local and I have not test driven it yet. I don't believe the engine has been rebuilt & pistons are stock to the best of my knowledge.

What questions should I be asking? What could be the cause of such low compression readings?

Thanks in advance!

-john

If the compression was tested whilst the engine was cold, it could give you those low readings - ask your wrench?

since they were able to chat w/ me after testing 3 cylinders, the engine could have definitely been cold. if it was cold, should i have them redo the test? it would seem to me that cold compression & leakdown could give misleading results...

Depends on the gauge being used, use 10 gauges you get 10 different readings. So long as the delta is +/- 5 to 8psi per cylinder across all 6 you are good. The key with compression is cylinder consistency as opposed to say 160psi. I have two compression gauges at home and their both will produce different readings on the same engine.

BTW leakdown seems fine.

A 90K 964C2 engine is barely broken in...TONS of life left in that badboy!
Yasin

I don't believe 0% on a 21 year old, 90k miles car......

Is this the seller's mechanic or did you get it to an independent?