plymouthcolt

I am interested in a 1996 993 with 77,500 miles. The owner had a leak down test performed and these are the results:

#1 - 4%
#2 - 4%
#3 - 3%
#4 - 3%
#5 - 4%
#6 - 2%

Based on my limited experience I think these are descent numbers? Yes? No?

wellcraft290

yes good. really heard anything under 6% is good to very good. below 10 is good and above 10 is time to start saving up for rebuild.

No HTwo O

Numbers look good. And the varience between cylinders also looks good. I assume the report is recent and you trust the seller's provided report.

plymouthcolt

I would get my own ppi, but I was just checking for good numbers before spending the money.

tj90

I say bull****. 2-4% leakdown on a 77k mile engine? I think this article is required reading:

http://www.carcraft.com/techarticles...ter/index.html

My favorite quote from the article:

"Everyone wants to have a hero engine, but don't believe all the hype you hear about 2 percent leakage engines. No cylinder seals perfectly, especially if the engine is nitroused, supercharged, or turbocharged where the top and second rings are set with wide ring endgaps. Even for normally aspirated engines, respectable leakage numbers would be anywhere from 8 to 12 percent with a variation between cylinders of 4 to 5 percent, but it's possible the variation could be as high as 10 percent."

It goes on to say that leakage of 20% on all cylinders is only worth 20hp on a rebuild!!

I realize this is not porsche specific article but Im pretty skeptical of the numbers that are posted on the board! Be wary of the PPI and the mech whos quoting them.

FYI, I was able to manipulate leakdown numbers on my engine by gently tapping the tops of my valves when my motor was out of the car. There is no way a mechanic would do this during a PPI. After doing leakdown myself I put much less faith in an absolute numbers for each cylinder. I also realize that there is separate leak paths for each the intake and exhaust valves. One number for each cylinder doesnt tell you where the leak is going. Id be less concerned about exhaust valve leak than intake leaks.

Good luck

Steve Weiner-Rennsport Systems

If I might add,.......

With all due respect to you & the owner, YOU are the one who should commission the PPI (and leakdown tests) for any potential purchase, not a current owner. This is a case of maintaining objectivity and preventing any conflicts of interest.

Those figures look very good, but I'd have them confirmed by your own mechanic, just to be sure.

stahwille

leakdown testing is only as good as the person performing tests. I.E. The test tool should be regulated for consistent air flow to meter. (painters understand ) after chooseing a n input say 100 psi max(this is to prevent unwanted rotation during test) one must calibrate leakdown test to 0% . easly done with no place for input air to exit! then select which cylinder to test first. 1-6-2-4-3-5 is always a good way to minimize confusion. Just remember a 4 cycle engine rotates 720 degees . so devide 720 into the # of cylinders say 6 and we always know the next cylinder to fire tdc is 120 degrees from wher you start. You can see these hash marks on most any 911 front pully! Also never be afraid to reseat a valve with a love tap , esp when you detect a leak / noise escaping. Anyone who's been around knows what can happen to an engine being rotated by hand after removing spark plugs! this thing called carbon comes to call . don't be fooled by leakage until you prove it ! spank the suspect gently or not / not so gently while under pressure with a soft mallet. you might learn something that smart people would like to keep to them selves. If any one is out there I'll finish by clarifing how to test for worn out valve guides OK? rotate engine until cam lobe is lifting valve stem off i'ts seat, then simply apply leverage to valve stem and watch for latteral movement. New has .0025 worn out has .025 thou. dangerous is woble woble ya..........MJ

stahwille

Gee I forgot to mention new porsche engines leave the factory with leaks 1- 5% is perfect. consider the ole iorn chevys left GM daily w 50% oh what feeling....

Stuttgart951

When I sold my 951 with 95K miles, 25K of which were in spent in excess of OEM boost levels, not a single cylinder was above 5%.

TheOtherEric

These numbers are feasible, but they're low enough to make me a touch skeptical. Since the owner provided them, they're not reliable unless you've spoken to the shop who did it.

tj90

Obviously a hero engine that you shouldnt have sold!