Baby

In researching an 87 coupe for purchase, I called the Porsche shop the owner told me had worked on the car in the past. The shop owner told me the car had been in not too long ago for a ppi and it had a few oil leaks (from where, he didn't recall) and one of the cylinders showed about a 15% leak. Otherwise, he said, it's a great car. I like the car quite a bit. It's exactly what I'd want, ideally. The asking price is toward the upper end of my range. It looks well taken care of, but that someone got a ppi and walked away makes me wonder.

My question is this: assuming there is indeed a leak, were I to have the car inspected and buy it, would I need to rebuild right away?

raspberryroadster

imo, as a general rule of thumb on a leakdown test 5% would be outstanding, 10% good, 15% acceptable, but borderline.....approaching 20% wallet time.

you also want to have a compression test done on all cylinders, which will hopefully show relatively consistent compression (p.s.i.) for all cylinders.

most of the cars feature an oil leak or seepage, but your new p.p.i. should identify extent and localtion

Ed Hughes

My guess is the 15% would've turned someone off, if the seller won't budge on the price accordingly.

Baby

Raspberry---just the information I was looking for. And Ed, that's my hunch, too. I understand there can be variances on leakdown numbers based on methodology---guess I need to decide whether to have a full ppi or to pass. Decisions, decisions! Thanks again.

87turbo87

Question...does the fact that a 15% leak showed up on one cyl automatically imply that a compression test will indeed show inconsistent compression across the cylinders? Meaning..what's the point of doing a compression test if a leak-down has already been done? The question I would ask is where is the leak coming from? Intake? Exhaust? Rings?

Ed Hughes

This is where a good mechanic can help during the ppi. A compression test would help ID where the issue is.

rusnak

a bit too many unknowns to wade in on this on the internet. A second test might show different results, and besides, you would want to know the other cylinder leak results too for comparison. I agree on the 15% borderline, another reason to do it again.

misterbeverlyhills

I had a %20 on 1 cyl at my PPI and the (race bred) mechanic stated he didn't fully trust it, had the same on his own 993. Everything else checked out great and I stole the car thinking valve job soon. 18 months later it is one of the tightest, smoothest and fastest 964s around, tracked regularly and I have not spent a penny on the motor, just brakes and tires.
Normally I would have run from this number but the car was all there, had been well maintained by a POC member and just ran so well I rolled the dice and so far so good, I couldn't be happier: Cobalt Blue with a 2 tone blue interior was worth it to me for the money.

Droops83

I generally like to see less than 10% leakdown on 911s; in fact many really strong 911 engines I've tested have 5% or less.

As for the engine you are referring to with 15% on one cylinder, what were the numbers for the other cylinders, and where was the leakage from? There are several possible variables in leakdown testing, one being engine temperature (sometimes a more tired engine will show high leakage cold but improve when warmed up), and you have to reset the gauge needle to zero each time before hooking up to a new cylinder. The regulated air pressure needs to be consistent for the test to be accurate (100 PSI is the general standard). Also, different gauges can read differently.