Spyder34

About to join the 993 ranks...leakdown and compression test results on a 1997 993tt below. A very reliable shop who performed the test says the results look great (shown below). Seems strange that compression is identical for 4 cylinders and the other 2 are very close-- and leakdown, while consistent among cylinders, appears high. Any help with interpretation would be much appreciated. Car has 28k miles and PPI is clean. Pictures to follow once I get the car. Thanks!!

We performed the compression and leakdown and it looks great. (just what we anticipated) Here are the numbers. Everything is within specifications for this vehicle.
Cyl#
1. comp. 135psi., leak down 12%
2. comp. 133psi., leak down 12%
3. comp. 133psi., leak down 14%
4. comp. 135psi., leak down 12%
5. comp. 135psi., leak down 12%
6. comp. 135psi., leak down 12%

looking good!!!!!

Mike J

Hmmm - I consider an excellent engine at 2% leakdown or less (basically at the lower limit of the gauge), and 8-10% not great, and 12% getting too high. At 12%, you would hear air leaking (like a hiss) at either the exhaust pipe or intake manifold (since the IC has to come off). Did they comment on that? What gauge did they use? What temperature was the car at?

Given they got the same readings off all cylinders, did they zero their gauge properly, since its unusual to get exactly the same leakdown on all pistons if there are issues.

Your compression is about right for a Turbo though. Getting to a two pound tolerance is also a bit more than I can typically do.

Did they repeat the tests to confirm?

Cheers,

Mike

vincer77

Leak down numbers do seem high to me.

AC/911's

Psi's not really matching %'s?

Dr. No

Leakdown seems high and compression seems low, although consistent, which is good, and I understand different machines read differently and I don't have experience with Turbo numbers. But for a car with 28k on the clock? Did you get any feedback from the PPI shop on a visual inspection of the valves? A good 993 tech can often judge the need for valve work by the play in the valves. Anyone tell you how much oil the car burns?

P-daddy

Agreed!!

Spyder34

I just spoke to the tech (Gold Meister at independent shop) who did the test. The compression test was done at 35 psi- that is the tester he uses and he says you odn't need to use 100 psi to test the cylinder. Thought the car ran perfectly. Impressed upon me that many fators go into the readings. He thought the psi readings were right in the range and that the leakdown %'s were well within spec (he would consider up to 15% or more to be within spec). Also impressed upon me the consistency of the readings. Engine was warm (and test being done in Costa Mesa, CA). I will follow-up with some of the other questions you guys mentioned above.
Thanks much!

deekay911

I guess 12% of 35psi is around 4psi, which is 4% of 100psi. is that how the numbers work?

Quadcammer

I call bull. First, those results look just a bit too even. That said, I had 150psi give or take about 3psi for the compression test on my turbo.

12 to 14% leakdown is damn near top end rebuild. I think i had one cylinder at 7% and that put me on the limits of comfort.

If you are really pleased with the car otherwise, id have a new ppi done at a different shop,.

Spyder34

Same tech did PPI and LD/Comp test. PPI revealed minimal oil seepage. I am having 30k mile maintenance done by same shop...so valves adjusted and plugs changed. No CEL issues and tech says car runs extremely well. Current owner (22 months) has driven the car 1200 miles and hasn't had maintenance done since oil change in 3/11. He says no oil has been added and oil level was spot on. Tech is confident in the test results. I'm paying top $ so I'm placing much reliance in tech and shop. Will check on gauge reset and air leaking hiss from tailpipe in morning.

Vorsicht

I, too (and two,) call bull. Strange things are afoot at the Circle K. Did he really do a leakdown? If so, where is the leak coming from? A key question for the service tech.

Chris M.

With that kind of mileage, especially the 1200 in 22 months, I'm wondering if this car might benefit from an "Italian tuneup."

Quadcammer

valve adjustment huh?

993s have hydraulic lifters and therefore don't need valve adjustments.

Please tell me this shop is not charging you for this.

Spyder34

Not sure I've ever seen this-- but sure would be nice if this were the case-- any ideas on this extrapolation?

Steve Weiner-Rennsport Systems

If it were me, I'd get a second opinion and leakdown, given the consequences at stake here.

One certainly doesn't want to pay top $$$$ for a car that needs an upper end rebuild as thats NOT cheap on a TT.