Feedback on Leakdown Numbers requested
 

Hey all.. the PPI on the car I'm considering has been performed. Here are the leak down results:

Leakdown -
#1 12%
#2 8%
#3 20%
#4 14%
#5 10%
#6 17%

The mechanic mentioned that a car which hasn't been driven much in the last two years (2000 miles in 2 years) could stand to improve those numbers given a tank of gas with Techron... the idea being that the carbon could be blown out.

20% worries me. Should I be worried?

Comments? This is nearly the last nagging issue in my mind before I pull the trigger on this car.

Thanks
Dennis

As a reference, I had a leakdown done on my PPI and the numbers were 1% and 2%.

Those numbers sound terrible. Yes, I would be very worried. Don't people say to keep it under 5% or so? A friend of mine just did a leakdown on his '91 turbo and the numbers were like 2-4%.

Oh, and if I wasn't clear enough, RUN AWAY FROM THIS CAR AND NEVER LOOK BACK.

IIRC, those numbers seem high compared to the leakdown test done during my car's PPI. I think my #'s were 4% with one cylinder being 8%.

Oh, p.s. are you sure the tech knew what he was doing? Those numbers are just so extremely high.

If the test has been done properly, those are not great results. Ideal numbers should be around 1-5%.
with 6-12% being just okay. Anything over 12% should get your attention and might mean the engine needs further diagnosis or repair. If you do a search, I know Steve Weiner has written about this numerous times.

This is a reason I never use leakdowns anymore. I can not begin to tell how many cars I have seen have horrible leakdown #'s but were terrific cars. I now only use compression and the just look for uniformity between them. I have seen huge disparities on race winning GT3 Cup cars on leakdown numbers from brand new Cup cars to ones with over 100 hours....just does not seem to be the best way to look at these cars whereas compression is easy to look at just need to make sure it is warmed up and has a good strong battery. Just my thoughts...

The tech that did this test is Mark Cummings at Autosport Engineering. I would assume he knows what he's doing since he was recommended from a few rennlisters.

I should re-emphasize... car has only run for 2000 miles in ~ 2 years. A few mechanics suggest that an 'Italian tune-up' and a bottle of techron would improve these numbers.

Finally, Mark said he was very surprised by the numbers because he felt that the car pulled very strong.

Ugh, I haven't a clue what to do next...

A PPI on my 95 C2 with 64k had compession from 206 to 213 psi for all cylinders and leak down between 1.5 - 2.5 %. Do you have compression #'s?

No compression numbers. I'm thinking the car should go back tomorrow and have that done.... <sigh>

Better to be safe than sorry.

Definitely!

I spoke with the seller.. going to do a week of hard driving with Techron and see if that improves the issue.

Thanks
Dennis

Hey Dennis - If you need someone to drive the car “hard” just call. Seriously I agree with Kelly better safe than sorry. Have the owner run the car and retest it. Mark definitely knows what he’s doing, I’d trust him…he has no interest in steering you wrong.

The car looks good but as you know there's always something better; you need to be satisfied with the car.

Nothing a track day wouldn't cure (more than likely).. If the car is something you really like, have the owner retest after some hard driving..

I agree with Glen on this. A leakdown tester should be used to pinpoint the problem of an engine that is known to have a problem. It is not an accurate way to determine an engine's general condition.

I have had engines with 45% leakdown in one or more cylinders perform perfectly. Others have had great leakdown numbers and used tons of oil.

On a 993, the thing to be concerned about is the valve guides. Neither leakdown or compression testing is going to show bad guides unless they are incredibly worn out.

Chris Cervelli
Premier Motorsports