jstyer

I too was curious as to the "valve adjustment"... Sounds a bit fishy.

Mike J

I have never heard of a leak-down test at 35psi - the leak-down is a % of the air pressure being lost (or having been made up) at 100psi by definition. 0% leak-down is zero leakage. I do not know if leakage is linear, I suspect not since a leak may not show up at 35psi that will show at 100psi.

Get a second opinion for sure, it's cheap insurance for the amount of money at risk. By no means is a compression and leak-down the definitive answer, but its a strong indicator.

Caveat emptor

Cheers,

Mike

sonny1

A second opinion is in order here.
Sonny1.

bobt993

If he is going to adjust the valves have him inspect the water pump at the same time........ Second opinion needed.

NC TRACKRAT

It would be nice to know the name of this "very reliable" shop so others on the Forum can avoid a similar waste of time and money.

chsu74

Blinker fluid may be low. What did the shop say about that?

LimeyBoy

Just looking at the maths, it does not matter what pressure the leakdown test is performed at, you are simply calculating leakage as a percent of the starting pressure.
However, if all tests are always done at the same pressure everywhere then the % leakdown values can be compared across the board as a common currency.
It would make sense to perform the test as close to 'operating' pressure as possible because you are checking the sealing function of the cylinder.
If you have a set leak path (doesn't change) and record leakage values at 35 Psi then as correctly stated earlier, raising the pressure to 100Psi will result in a larger leak value through the same leak path.

It may be that the tech had an issue with the setup or equipment (would explain the identical results maybe) but regardless, going off the cautionary reaction to those % values in previous replies by knowledgeable RLr's, if I were to drop top money on this beauty I would maybe take the time and relatively little more $ to re-do the test at whatever is considered the ideal or official pressure for 993TT leakdown (thinking compression ratio + inlet pressure as considerations).

I hope this TT does pass every inspection with flying colours and is a great buy for you. Good luck.

Spyder34

Thanks for all of the feedback. I think a second opinion/test is in order-- as the car in all other respects--checks out very well and I'd rather not walk away. I almost didn't even do the LD/Comp as the car runs well, boost is normal, no CEL and no excess oil seepage. The shop is the sponsor of this forum and in all other respects has been absolutely great. I am just trying to reconcile their comments with all of yours. I test drove the car and it pulled hard-- but I have little prior 993 experience and was in the back of the line when shop knowledge was handed out. Fortunately the sale is contingent on the test and I may have to delay the $ outlay for a few days until this is settled. Your candid comments are much appreciated!

chsu74

Hopefully the shop will make it right or not charge you for the PPI. Post pics when this car arrives at your driveway.

Dr. No

Spyder, Steve is like E F Hutton. And if they actually said they would do a valve adjustment on this car I would be concerned.

Mike J

Hmm, not sure if I agree. It seems to me that at 100psi, you might start to observe leaks that do not happen at 35psi, so the reading could be different. I mentioned that in my post. For example, the rings may be able to hold a 35lb pressure fine, but at 100psi fail a bit (like you said, closer to operating pressures).

cheers,

Mike

doc_porsche

Would testing at a higher psi yield a higher leak percentage? If I pump my tires up at 15 psi it might not leak as much if I pumped it up to 100 psi if there was a hole.........just brain storming

Vorsicht

OK, we are somewhat OT but....

Generally speaking, with pressures we are talking about here, increasing the input pressure does not increase the percentage of leak. If you increase the pressure the air just goes out the hole at a higher rate. The percentage of air escaping is the same.

Now, if you increase the pressure to a point where the air can not escape as fast as it is coming in (way higher pressures) the system will become stressed and eventually explode.

What is important, however, as Mike state's above, is having the pressure high enough (100 psi) to be able to hear where the leak is coming from. I learned the hard way that a leakdown test is useless unless you know WHERE the leak is (intake, exhaust, breather). Knowing where the leak is tells you where to find the problem.

Spyder34

Given overall condition of car including no other indications that engine is compromised, consistency of cylinder readings and reputation of shop (valve adjustment comment aside- maybe I misheard him and didn't know better- although I do now!), I'm going to continue with the purchase. Here are a few pics...wheels are getting changed and tint is being removed-- so I'll add full view "after" pics once it arrives...

MarkD

Looks fantastic and is likely healthy
Congrats!

The leakdown was not done properly, no way around it
But I doubt there is a problem with the engine

Looking forward to more photos!