Cylinder #3 leakdown

[Jameel]

I've been looking for a 911 coupe since last summer. I've found a number of cars that met my criteria, and so far I've had ppi's done on four cars. Three of these were well-kept cars in the 80k to 110k mile range, and they all came back with leakdown percentages from 35% to 50%, all on cylinder #3. All cars had good numbers (less than 5%) on remaining cylinders. I'm coming from a VW background and I've learned that #3 cylinder (left of case, closest to flywheel) tends to run hot on VW engines. Could this be the case with the flat 6 as well? And is this the reason that valves go bad on 911 #3's head?

On one of the cars the mechanic said the leaky cylinder was caused by a "burnt valve" and that the repair would cost an estimated $6000. I'm pretty new to this, but that figure seems to be approaching the cost of a top end rebuild ($8k to $10k), but for only one cylinder head. Can someone explain why overhauling one cylinder head would cost $6000? Doing the math that means a complete top end would be $36,000 from this particular mechanic. Even if you bumped that down by $10k, still seems way way off to me from what I've researched.

If you had a solid engine with excellent leakdown except one cylinder, why would you mess with the other cylinders? Yes, "while you're in there" and all. But I'm serious here about just fixing what's broken. Do folks do this?

With my luck, at times I feel like there are no healthy 911's out there.

[prschmn]

#3 and 6 are usually the ones who suffer when critters have made a nest. I'd agree that 6K
is a lot for repairing just one but remember in order to get to it the whole left bank has to be removed so "while you're in there".
Depending on how it's been driven it could easily have enough valve guide wear to warrant
replacement. I'd rather buy a car with an "issue" that can be used as a bargaining tool but
suspect the guy doing your PPIs is not the one to do the work.

[Discseven]

JAM... $36,000 = jet engine rebuild. Small jet engine.

To fix or not to fix is a good question. A Porsche with low compression on one cylinder is not a big deal IMHO unless you're a perfectionist... or need to have all edges sharpened for the next race. Given the price quoted---which I consider high---I'm immediately questioning everything else the same individual would propose... such as a burned valve. Did he scope the chamber to make that determination? Did you see the vid? Are you sure the vid was your PPI car's cylinder? If yes... OK then. But $6k. That's not getting my vote. To replace a valve and seat is a 3 day job for someone who knows Porsche and who has the needed equipment in-house to replace the valve guide & seat and make any necessary grinds/laps. Parts mentioned are negligible. (Once an engine is entered, there is typically more found that needs attention and is best attended while in hand. Perhaps the mechanic is accounting for this.)

If you're not working on your own car & components, allow me to suggest (from my own pain & suffering) the first thing you want to find, before getting a Porsche, is a Porsche specialist in the year/model Porsche you will have. Equally important is it being someone who is worthy of trusting to a very high degree. When you have this, then the car you have will be in good hands and you can be confident the money your investing in whatever is well spent.

Good luck in finding the right car for you!

[Jameel]

Thanks. I did not see a video, or what methods the mechanic used to come to that conclusion. I should have asked.

I do plan to work on the 911, since there aren't a lot of options in my area. I do know a few retired mechanics who spent their lives working on these cars, so I have some brains to pick. Plus a close by 911 owner and ethusiast who knows the cars. He's sort of been my mentor the past few months, he's owned 911's since the 70's. I'm fairly mechanical myself, so with Wayne's and Anderson's books I think I'll be in fairly good shape.

I'm not a perfectionist, and would not have a problem driving a leaky car. All the owners of the cars I've looked at had no idea if their cylinders were leaking before I got the leakdowns. I've passed on a couple cars now with these problems due to owners who were holding out for better money. Good guys the lot of them, but the current atmosphere doesn't favor buyers much.