Old Charlie

When I bought my 993, the senior tech (since 1964) away from home said, "I never do a compression, leak down test on these motors. No point. I run the car and tell you about the motor from there" Car runs fine for long time. Entrance ramps carefully done, very fun.

Car never tracked. Makes 22-24 mpg. Always on Mobil 1.

New buyer (I'm moving to turbo) wants to use tech who is a new P-car guy, also works on BMW, Ferarrrrris (ouch, not German), and etc., who may want to do leak down, from what I see, he looks at your wallet and goes from there.

My thinking, why waste time/money, excercise plug threads, etc.

What do you all think?

Hope storm doesn't hurt any Porsches up the NE coast.

Y'll take care, Charlie

pirahna

Penny save pound foolish.

Compression check and leak down is a must for me.

JPS

Suggest doing a search. There are multiple views, but it seems to net out at it is a good data point, even though there is high variability as to how well someone does the test. But it can reveal large problems. From what I can tell, most seem to go for it. I personally have had it done on all 3 of mine, past and present.

Marshy

+1. It's cheap insurance.

Geoff

dr jim

I agree that, if done properly, a leak down and compression test can reveal a lot about an engine's condition. However, several mechanics I really trust have told me they don't think it's worth doing for two reasons. First, if there's really something wrong with the engine either the check engine light will be on, or an error code will show up when you do an OBD scan.

Second, it's really time consuming to do a leak down test on these engines (when they're in the car), which means it's really expensive. The basic mechanical aspects of performing a leak down test are relatively simple (e.g., bring engine up to operating temperature, rotate engine until cylinder is at TDC, check leak down, etc.). However, these air-cooled engines are designed to lose heat very quickly - without any coolant. Therefore, in the time it takes to measure leak down and compression on one cylinder (e.g., remove engine components to access spark plug, remove plug, hook-up equipment, take readings, remove equipment, replace plug) there is a good possibility the engine has cooled down sufficiently that some (albeit small) contraction has occurred in internal components (e.g., piston rings, valve guides, valve seats/faces). This means that if you now proceed to read the other cylinders there is a good chance of small but significant measurement errors occurring - possibly enough to erroneously conclude the engine has premature wear on one or more cylinders. In order to avoid this problem the engine must be re-assembled sufficiently to allow it to be started and run for enough time to return to full operating temperature. The engine must then be sufficiently disassembled to allow performing a check of the next cylinder, etc... To make matters worse - it's really hard to do this disassembly while the engine is hot, due to the really limited work space in the engine bay. Of course, this is all pretty simple if the engine is out of the car - but this is usually not feasible.

Just my $0.02, and I am sure many will disagree.

Texas993

Charlie is asking the question as a SELLER. And it is more about allowing it with an unknown tech.

Charlie, I wouldn't be too concerned about it. However, ultimately, you shouldn't let anyone unfamiliar with air-cooled Porsches touch it! Your call.

Good luck with the future turbo!

Kein_Ersatz

Yes. Had it done on both cars. If the cost is an issue (waste of who's time), then this probably isn't the brand for you/them, as sometimes they can cost a few $s to maintain, but worth the assurance of a healthy engine when delivered into your/their hands. To 99%, with 1-cyl (#5 for example) weak / leaking, the engine will run fine, but will not perform to its capability and will lead to other problems.

To mechanic, this may be a job not desired, but he/she will not be the owner / custodian, you/they will.

But you should have a say in who works on you car until you sell it, so if not happy with inexperienced shop / wrench, point the buyer in a different direction. You don't want a noob learning on your car for a leakdown.

tonypai

Charlie

Absolutely not, I wouldn't let a strange mechanic unfamiliar with Porsches touch the engine. A full leakdown/compression test will require a lot of time and is very invasive. My personal mechanic refused to do a leakdown/compression test without the sellers permission and it would have doubled the cost of the PPI.

I also understand the importance of why the buyer wants it done. See if you can find a common mechanic who knows these engines and have them to the tests.

Good luck.

Tony

il pirata

As a seller I would not let any mechanic do a leakdown etc that I would not use to service the car. FWIW in the Denver metro area that would mean only a couple of shops for me...maybe.

Quadcammer

on an NA car, the lower plugs are pretty accessible.

on a turbo, its a real pain.

either way, unless the tech is a real noob, I don't think its wrong for your buyer to request this

Quadcammer

how is it very invasive?

Mike J

You have two questions you are asking. One is giving your car to a tech who does not know 911's - OK its within your rights to refuse that, and ask for the car to be taken to a tech who knows the cars.

The second is around the viability of doing a compression/leakdown.

Are you going to do a compression/leakdown on your Turbo purchase? You are not being very smart if you are saying no. Same goes for the new purchaser of your car.

Effort is the same as a plug change, only 6 plugs are needed. Its is not "invasive", we are not talking about a scope up a rectum, just a plug change. On a NA car, its not an issue, most of the plugs you can get from the bottom, a couple from the top. Easy. On a turbo, more work for sure, stuff has to come off and access is much tighter. I have done several, and its very doable.

For the Buyer:
I think any tech who tells you not to do this on a used car is an idiot. Period. Its not his money, it's yours. I just failed a PPI on a $80,000 Turbo on a compression/leakdown test - the engine was just rebuilt (at very low miles) by a local tech who thinks he walks on water -> I recommended to the buyer that we check it anyways even if it had only 50 miles on the rebuild. Low and behold, one piston had low compression and 25% leakdown. I tested three times (including a startup inbetween - people who know turbos know how much pain that is) with the same results. The deal dropped. BTW, in this case, the car seemed to run fine, pulled strong and had no indicators/CEL's (reading from the PST-2). Many times, you cannot tell buy just driving the car or reading the codes.

At the time, that tech thought doing a compression/leakdown was not required - I call total BS on that. I feel strongly about this, if someone is going to spend multiple thousands of dollars on a car, does it not makes sense to know as much as possible.

For the Seller:
When I sell my cars, I do a compression/leakdown BEFORE selling it and then I have that evidence for the purchaser - it shows a proactive approach that will help sell the car. If I find problems, its up to ME to take care of it, or make sure the purchaser is aware.

Be aware, Karma can be a bitch.

Cheers,

Mike

Texas993

Nicely stated Mike!

Mike J

Yeah, getting tired of the "should I do this?" and "my tech said this, and since he knows everything there is to know about these cars, he must be right" sort of questions. I find it amazing how much money people will risk without really checking what can be checked relatively cheaply .....