Importance of Leakdown and Compression Test in PPI

[OsoMoore]

I'm getting a PPI done, and the company (European Performance in Raleigh, NC) doesn't do leakdown or compression tests by default, but I could request it.

The car I am looking at has a good history and a rebuild about 40K miles around 9 years back, done by a well-known pelican. How important is it to get leakdown and compression? I don't mind paying for it if its necessary, but saving money is always good - more funds for tools later.

[bullethole]

without compression and leakdown, you have no idea as to the actual health of the engine. even if its been rebuilt by a reputable person, things do go wrong. Worth the $'s

[wildcat077]

You mention saving money is good ... by doing a leakdown and compression test you could save yourself a LOT of money should the engine have any issues before you buy the car

Definitely a wise investment !

Cheers !
Phil

[john walker's workshop]

what kind of PPI is that??

[OsoMoore]

Hmm, I re-checked my handy PPI link and noted the following:

25. If no broken studs/pulled studs are found proceed with a leak down test. (Although some disagree, I feel that a compression check on a 911 is often useless, while a leak down test is invaluable. A knowledgable mechanic can use the leak down test to assess the condition of several important engine components, like valves and rings.)

I'll make sure to have at least the leak down test.

[Tippy]

Originally Posted by john walker's workshop

what kind of PPI is that??

I LOL'd. What is the point of NOT doing them in a PPI? Those are the most important checks and if not done will probably cost the most money if there is an issue.

[gregwils]

Yeah, other than a screwed up tub, a bad motor will have the biggest bite.

[Hnichols]

When I recently had a PPI done for a Carrera, the mechanic didn't think the leakdown was all that vital, because it doesn't tell you anything about worn valve guides, which is the weak link on the 3.2 motor.

I know Peter Zimmerman writes in his book that the leakdown is essential, but I wonder if compression check and an inspection of the valve guides does not give a sufficiently good sense of the overall health of the motor?

How much extra does a leakdown add to the PPI?

[Rot 911]

Originally Posted by Hnichols

When I recently had a PPI done for a Carrera, the mechanic didn't think the leakdown was all that vital, because it doesn't tell you anything about worn valve guides, which is the weak link on the 3.2 motor.

I would get another mechanic.

[Christien]

Originally Posted by Hnichols

How much extra does a leakdown add to the PPI?

Maybe $1-200? It's a no-brainer, IMO. Most PPIs I've had done run $250-400, including compression and leakdown. I can't imagine doing otherwise on a 20+ year old engine.

[Tippy]

Originally Posted by Rot 911

I would get another mechanic.

Yes

[john walker's workshop]

leakdown tests don't tell you if the guides are worn, but they show the results of worn guides, ie: worn valve seats. valves tend to be thrown onto one side of the seat when the the guides are sloppy, which wears that area more than the rest of the seat, so, out of round/eccentric seat plus round valve = higher leakdown results. 911s don't burn valves much at all. the seats wear out instead.

[dshepp806]

Get both leakdown and compression tests. JW and others have often mentioned why, as they test different things, actually.

Any mechanic who knows these cars, knows that (period).

Best,

Doyle