Leak Down and Compression test results. How bad are they?
 

1977 911S 2.7L

Recently had my engine rebuilt by a factory trained mechanic (he is the local Porsche guy and rebuild these all the time) it now has only 3500 miles on it.

The rebuild included new rings, replaced studs, rebuild on the heads, line bore etc.

At around 1,000 miles I noticed it starting to smoke and consume oil. Now it smokes considerably and if it is left for a week or 2 with out starting, at start up it fills the neighbourhood with smoke for at least 5 minutes.

Here is the data from the Leak down and Compression tests.

Tested with 10 minutes after full operating temperature. Leak test done first.

Leakage test / Compression test
#1- 45% / 115
#2- 18% / 145
#3- 38% / 145
#4- 35% / 140
#5- 20% / 155
#6- 20% / 145

What does all this mean and should the engine come apart again.

Your help is extremely appreciated. I will be taking my finding to my mechanic to get this resolved so I better be right!

Thanks.

Paul

If the leak down numbers are accurate, it needs to come apart and see what happened. Fresh motor is around 2-5%. A motor in good condition shouldn't exceed 8-12%. When doing the leakdown listen for the air escaping. Intake=intake valves, exhaust=exhaust valves, in the case=rings. Sounds like the rings either didn't seat, or broke.
good luck.

How long has the car sat after the rebuild?

Just to give you an idea, this cylinder had a blown head gasket and 12% leakage:

http://forums.pelicanparts.com/uploa...1181608072.jpg

http://forums.pelicanparts.com/uploa...1181608123.jpg

The car has not really sat. It has been driven and started every week or two since last October. The car does not drive badley. It has good power and runs fairly well. Although, I am comparing it to what it was like before the rebuild which was tragic. pulled head studs, used more oil than gas but still fun to drive. Air noise was comming from the oil spout and other spark plug holes. None in the air box or tail pipe.

Paul

Paul,

What was done to the case? I was guessing that your rings did not seat or maybe broken rings as mentioned above.

Your rebuild sounds very much like mine - I have new rings in 180K cylinders and rebuilt heads. I have no smoke - only a quick puff on startup. My case was gone through with a fine toothed comb - much work done in there.

Case was line bored, surfaced and cylinders checked for roundness and honed by an experienced machinest who specialises in Porsche cases.

Paul

Obviously something is wrong. Why not just take it back to the mechanic that rebuilt the engine and tell him about the smoking, oil use and leak down/compression numbers. If he is a stand up guy he will do his best to make things right. If he isn't, doesn't matter how much evidence you give him, won't matter.

That is my intention. and I am sure he will take care of it. I just wanted to educate myself on the leakdown procedure and acceptible %'s before bringing it to him.

Your input has helped me, much appreciated.

PK