Compression and Leak Down tests

[Greg986]

I am going to have compression and leak down tests done on a 2000 Boxster S with 94,000 miles on it. What should the

readings be to indicate a "good engine"? Thank you for any info you can provide, Greg

[JFP in PA]

8-12% would be an extremely tight engine, with that kind of mileage 15-20% would be realistic; anything over 30% would be an issue.....

[Greg986]

8-12% would be an extremely tight engine, with that kind of mileage 15-20% would be realistic; anything over 30% would be an issue.....

Thank you for the quick reply. I will post the results of the tests later.

Greg

[Dallski]

8-12% would be an extremely tight engine, with that kind of mileage 15-20% would be realistic; anything over 30% would be an issue.....

Ok, that's for the Leakdown Test. Any idea what the compression readings should be on a standard Compression Test??? I'm also asking for a 2000 Boxster S.

[Loren]

8-12% would be an extremely tight engine, with that kind of mileage 15-20% would be realistic; anything over 30% would be an issue.....

Ok, that's for the Leakdown Test. Any idea what the compression readings should be on a standard Compression Test??? I'm also asking for a 2000 Boxster S.

The important factor in a compression test is the difference between cylinders. Since you are looking at different cars with different mileage they are not going to wear the same.

It would be highly unusual to find a car with all cylinders reading low (which would usually mean badly worn rings) - it just does not happen much anymore.

What is more likely is a cracked cylinder head, or a cracked cylinder sleeve or other valve, head or piston problems - on one cylinder.

So if you test all the cylinders and they are within 8 to 12 percent of each other - then all is good. If you find one cylinder that is much lower than the others then you have a problem in the cylinder (head, valve, etc.).

[Dallski]

Oh ok. Mine seems pretty much the same as Greg986's. Mine is a 2000 Boxster S with 102,000 miles. Warm engine, WOT readings for the compression test were 131, 133, 127, 133, 131, 129. I know high compression engines are supposed to have lower numbers than lower compression engines, but these numbers still seemed low to me. I guess I can't argue with a 6% maximum variance after 100+ thousand miles! Would be a waste of time to do a Leakdown Test now, right? And just for reference, because I searched for 3 hours and came up with nothing, what is the factory compression reading supposed to be???

[JFP in PA]

In good shape, the engine should compression test numbers in the low 140's (PSIG)...................

Edited March 11, 2010 by JFP in PA

[Dallski]

Thank you very much, I really needed that number. So mine's bit worn out, but still in good condition. Sorry for hijacking your thread Greg986, but it's pretty much the same thing you asked. Hope yours is in good shape!

[Greg986]

Thank you very much, I really needed that number. So mine's bit worn out, but still in good condition. Sorry for hijacking your thread Greg986, but it's pretty much the same thing you asked. Hope yours is in good shape!

No problem. Tbe more the better. All 6 cylinders of mine are in the high 140's and leakdown is less than 9%!

I wonder if this car has a newer engine in it. I have bought it and am flying to TN next week to pick it up.

Deals Gap and Cherohala Skyway here I come:)

WHat a great board!!! Thanks again everyone for your help, Greg

[sonicworld]

I too am looking at a 2000 Boxster S that a Porsche dealer in NJ is offering but I live in Mass. How would I go about getting these tests done?

[logray]

You'll have to request them from the dealer or shop doing the pre-purchase inspection.