bdhill

I am looking a 96tt with 44,000 miles at porsche dealership. Master technician tells me that there is no need for this test as an o2 sensor detects compression problems...I told them what I have learned on here; that it would foolish to buy the car without the test...
What does the o2 sensor actually do? It would be nice to think that he has some truth in what he said. I told them I would pay for the test, but they would have to agree to make any repairs indicated by the test. Sounds fair to me.

Thanks for any insight

stockboost

You can still have good compression while having pending valvetrain problems. A compression and leakdown on a TT with that many miles is a must.

ca993twin

I agree... get the compression and leakdown test. Put in fresh plugs while you're in there. It'll cost a bit, but the peace of mind is well worth it. If you are paying for the test up-front, then they need to agree to any repairs discovered, or reimburse you if you want to walk away. Get that agreement in writing.

I've never heard any discussion about O2 sensors helping to detect low compression problems. Good luck on the car. I hope its everything you want, and comes sailing through the PPI.

LeeR

When I bought my car in 4/02 with 47,000 miles, I had a compression test with excellent results, but no leakdown test. Shortly thereafter I had CEL that wouldn't go off, had leakdown test, showed out of spec in three cylinders, and then had valve job to remedy. Moral: get a leakdown test.

Kevin

bdhill;

There have been a few Rennlisters lately that have not had a leak down on the enigine. It has caused them to shell out monies for a new topend. Lee has mentioned his experience. Valve guides are the early culprit. Again spend the extra monies to get a leakdown and if you have a low hole at least you can go from there. What the Master Tech is telling you is, hey I don't want to a leakdown on this car.. Tell him, Hey if I buy this car, are you you going to install new guides for free, if something shows up in a few hundred miles...

Rob 97 993c2

kevin-
does a leakdown cover valve covers and gasket covers?
Or, is it just for valve guides?

LAT

FYI, and you can't always tell by "the seat of your ****" meter. I bought the RUF last year and she ran like a scalded cat and yet on leak down two cylinders were out of spec and the culprit was the top end. Luckily I had this done prior to purchase.

Leak down cost $330.00, cheap insurance I would say.

Kevin

Rob a leakdown just covers your piston rings and valves. Since the guides will wear the inside diameter of the guide, basically the diameter of the hole grows. The valve cannot seat correctly on the valve seat. You will get leakage past the valve.

If I was buying a high dollar Turbo "S" I would remove the valve covers and tap each valve to A)seat the valve against the seat. This is down while the cylinder is pressurized. B) With a screw driver pry the valve stem gently to see the play in the guide.. If at this time pressure was lost and the leakdown value went south, I would suspect that we have guide wear.. C) Not many folks are aware that once you remove the heat exchangers/headers you have a excellent view of the valve guide and the condition of any carbon buildup around the guide/valvestem..

As these engines get miles on them, guides are going to be a common issue. If you don't want to shell out the monies down the road, doing these few inspections can lower your financial exposure.