Got my PPI ......

rludym · 03-03-2011, 09:39 AM

ok - got PPI yesterday on 87 911 cab. Cyl #4 had 22% leakdown, all others less than 6%. compression at 175 on all. Other issues noted were small - typical of car with 205K miles (top end rebuild at 117K). Seller is a mechanic and did his own leak down and showed 4%. Called original mechanic and he said the rings could have 'reseated' and they may have 'slide back into place on drive back'. Is that feasible?

Vin-barrett · Vin-barrett's Garage

Generally I don't really put much stock into leakdown numbers, however 22% in the one cylinder indicates a problem.

something like rings reseating is unlikely. move on to another car

chaozz · 03-03-2011, 11:27 PM

Quote:

Originally Posted by vin-barrett

generally i don't really put much stock into leakdown numbers, however 22% in the one cylinder indicates a problem.

Something like rings reseating is unlikely. Move on to another car

+1

rludym · 03-04-2011, 05:43 AM

what do +1 posts mean on this forum?>

Matt Monson · 03-04-2011, 09:45 AM

Quote:

Originally Posted by rludym

what do +1 posts mean on this forum?>

It means he's in agreement with what the previous guy said. I also agree. Keep shopping unless you are buying the car to tear the motor apart and build it into something new...

DCinVA · 03-04-2011, 10:59 AM

Since the compression is 175 across all 6 cylinders, I would think the results of the leak-down test are suspicious. It is important to follow the proper procedure when doing the leak-down test on a flat 6. Basically the procedure is one cylinder at a time. I.E. rotate the crank to the proper position, remove the plug, do the test, reinstall plug. Follow those same steps for each remaining cylinder.

I have heard it said that when you pull a plug, sometimes a bit of carbon from the head is dislodged and drops into the cylinder. If you pull all the plugs at the same time, dislodging bits of carbon into cylinders, and then turn the engine over, those bits of carbon would be pushed around in the cylinder, and hence could become lodged between a valve and its seat as it opens and closes. If you follow the procedure outlined above, even if a bit of carbon falls into the cylinder when you remove the plug, the valves are closed, you do not rotate the engine, so there is no possibility of lodging carbon between the valve and the seat, which ruins the result of your test.

Having said all that, I would still be suspect of the car, and would probably pass on it.

rludym · 03-04-2011, 03:37 PM

I did it. Done deal - guy I bought from is owner of porsche shop out here and had his mechanic show me leakdown reading on #4 - at 3%

Danny_Ocean · 03-04-2011, 10:18 PM

Quote:

Originally Posted by rludym

...guy I bought from is owner of porsche shop out here and had his mechanic show me...

Hmm...no conflict of interest there.

DCinVA · 03-05-2011, 06:06 AM

Congratulations on the new ride. and I really like the color.

For what its worth, my 86 daily driver has 250k + miles and is still going strong. These cars last a long time if properly maintained.

Drive it, and have fun with it.

rludym · 03-07-2011, 01:56 PM

thank you and already had a great weekend driving it. 75 and sunny here in AZ and I put 200 miles on it with top down!...had an absolute blast. Told my girlfriend I already got 5K of enjoyment out of it over one weekend!