Compression test on '89 3.2 - waste of money?
 

Dear fellow Pelicans. I'm about to push the buy button on an '89 3.2. Drives flawlessly. No smoke, 100% clean engine, no visible leaks anywhere. Brown exhust pipe.

I've asked for a compression test, but the local mechanic (allegedly experienced porsche mechanic) consider it a waste of money.

Do you concur?

Edit: I meant leak-down of course!

You can do a compression test without a leak-down. It's quick and cheaper than a leak-down. Obviously not as thorough, but can give you some data. I would agree with your mechanic, though, based on the fact that there is no smoke and runs smooth, a leak-down is likely not necessary. But have him pull the plugs and look at their burn color. If all consistent brown, it's good. Then checking compression is easy. If those values are consistent across all 6, you should be OK. My $.02. Good luck.

You should get a compression test -- some 3.2 carreras (mine included) suffer from premature valve guide wear, which requires a top end overhaul to rectify. Compression test should clarify on this issue and a catalytic converter (if installed) would hide the telltale smoke. This can also be evidenced by excessive oil consumption (over a quart per 1k miles) even if no visible leaks.

waste of money. Drive and keep smiling

Oops; failed to read properly. If considering to buy I would advice to do a leak down test. Hard to judge the condition in any other way being new to the car

If it's just for your own peace of mind, go ahead. Heck, you have your cholesterol checked yearly, right? It's nice to know the numbers. But, yeah, unless you're diagnosing an issue, it's a waste.

Run as fast as you can and as far away as possible from that mechanic. He is not doing you any service at all. You cannot tell the condition of the engines internals from the outside.
An absolute must when buying an older car. If you don't and the engine has issues you have no one to blame but yourself.

Oh, didn't register it was a PPI. Yeah, agree with Mr. Racer here. If nothing else, you'll have a baseline.

Thanks for the reply guys - I've requsted the leak down. If it's good I guess I'll be very happy driving it home knowing it's in good working order.

Leakdown test won't show worn guide valves.

Neither will a compression test. Both the leak down and compression tests can detect worn rings and valves that aren't seating properly.

A compression test will NOT show bad guides or worn valve stems. With bad guides a valve still seats properly, yielding good results. Also, if you have worn guides, your catalytic converter will not hide the smoke. It will still show out the tailpipe on decel.

Compression and leakdown tests will show worn rings, worn intake or exhaust valve seat/valve head issues though, as well as bad head/cylinder seal-but you say engine is dry and this issues shows visibly.

An engine with good compression and leakdown numbers that consumes excessive amounts of oil likely has bad guides and/or worn stems...

Don't "run away" from the mechanic. Ask him why he thinks it is a waste of money.

Brown exhaust pipe, not sure what brown looks like, it is very subjective. That said it never hurts to have the tests done because they can yield good information, just not about valve guides...

Cheers

I almost did NOT do a PPI on one of the P-Cars I was intending to buy, which had all the power and torque in the world, but it ended up with almost two dead cylinders, which I did not buy in the end.