Guys, I don't really have much of a mechanical understanding of these readings, so in turn I ask for help. I've located a car and have been told of this data ('99 F355, 21K miles): "Found less than 5% leak down on all 8 Cylinders" "Cylinder leak down test was about 2 percent leakage on each cylinder. Compression test average was 180lbs." Do these numbers seem ok? If more data is needed, what should I specificically ask for? Thanks.
Those numbers look ok. You're looking for leakdown of less than 10% for individual cylinders. For compression numbers key is consistency. You want all 8 cylinders to have about the same. 180 is good I think....I remember seeing other PPI with 180's. when I did my PPI my compression numbers were at 230-240 range.
If a proper leakdown test was performed on a hot engine by a professional and yielded sub-5% leakdown readings, then you should buy the car before it is stolen out from under you. That engine will SCREAM!
Thanks for chiming in Patrick. In shining more light on the matter, I also found out that the compression test which yielded "2% leakage per cylinder" was done in '06 and the test that yielded "less than 5%" was done just a couple of months back. At what leakage percentage point does one suspect problems to arise? And on the compression, what does "180lbs" mean as oppossed to any other number? When should one start to question the "health" of the engine as to say that there is something that is going to be expensive in fixing? Sorry I am not mechanically inclined, so I look forward to gaining all the knowledge I can about this engine.
I'm no expert but I would get an independent test done -- a lot can happen in a year -- or a couple of months...
You need to have a fresh PPI done no questions asked! Anything can/could have happened between then and now.
With those leak down numbers, I would expect higher compression numbers. It is my understanding from dealer mechanics who have worked on these cars when brand new that none had 5% leakdown numbers. I was told by a highly reliable source they were all closer to 7-10%. With a good battery cranking the engine, compression should be 220+. Have an independant done.
Guys, thanks for your inputs. For an independent test / PPI, would franchised F-car dealerships be a good place to start?
Dealer is an expensive way to go and they will be very busy. A good independant would do you right. I know there are a ton down in your area.
