CP

Hi,

Here are the leak-down test results on a 993 turbo.

Cylinder #1- 5%, #2- 6%, #3- 6%, #4- 6%, #5- 4%, #6- 6%

Are these decent numbers? I do not have compression test results. Are those mandatory?

Thanks.

CP

viperbob

CP,

How are you? I hear that your car will be here before Thanksgiving. Can't wait to see it. Those numbers are maybe a little high, not sure the exact numbers for a 993TT. I don't think it is anything to worry about. You are generally looking for a cylinder that is WAY off the others. All cars leak down through the rings as there is never a perfect seal. It is just the rate that you are looking at and measuring across the cylinders. Race engines tend to be tighter, street engines a little looser.

You are looking at two different things with the two tests. I don't have time to go into it now. The compression test will also give you good information. Again, you will be looking for a similar pattern of consistency.

Steve Weiner-Rennsport Systems

CP:

Those numbers are OK,....Did they tell you WHERE its leaking from?

With all due respect for Bob, its not fair to say that "all cars leak through the rings as there is never a perfect seal". Thats not quite accurate. Most cars leak more from their valves, not the rings unless the pistons/rings/cylinder walls are worn or damaged. One looks for the percentage of air loss and the SOURCE of the losses.

The whole point of the leakdown test is to qualify what a compression test shows. The numbers are important for sure, but the useful aspect of the leakdown is that it shows the source of the leakage!

Most cars with some miles on it will leak through the valves from accumulated carbon, not the rings (unless something is really wrong) so its really important ask the technician where the observed leakage came from. Without that, the leakdown test results are out of context and not real useful.

Any proper PPI should include both compression and leakdown testing and the tech should tell you where any observed losses were coming from. Air losses from the air cleaner indicates leaking intake valves; air losses from the tail pipes indicates leaking exhaust valves, and air losses from the oil tank filler tube indicates ring or piston issues. Together with hot compression figures, one can get a fair assessment of the condition of the engine. Depending on mileage and whether I see the undertray, I'll pull a lower valve cover and check the guides, too.

CP

Steve,

Great education, as always. I just send the appropriate questions to Mr. Han's Lieb, chief mechanic at RUF. I will post the appropriate answers received.

This is great general, technical education for us all.

Thanks again.

Bob,

As soon as the car arrives, I'll bring it to pay homage at your garage.

CP

CP

Steve,

Bottom line question, looking only at these leak-down numbers, there are no compelling reasons to turn down buying this car, correct?

CP

Steve Weiner-Rennsport Systems

Hi CP:

As long as the hot compression figures are OK and the leakdown tests showed the air did NOT come from the oil tank filler, I think you'll be fine.

I'd run a few bottles of Techron through it while driving in a "spirited" fashion for a few hundred miles and change the oil. I think you'd find the compression figures will improve,....

Enjoy,

CP

Steve,

RUF is performing the 30,000 miles service on the car as we speak. Once the car gets here, I'll have someone local look at it again.

We all want a great car, but I'm also realistic to realize that a 95 993 will probably not be in perfect shape mechanically. Like OldGuy, I'll start a maintenance kitty for a rainy day. Or is that NOT a good thing to say to someone form the Pacific Northwest?

CP

Steve Weiner-Rennsport Systems

CP:

You are a funny guy,.... (the fall rains just started today)

Much like aircraft ownership, IMHO its prudent to start a maintenance-overhaul-modification kitty after purchase so one doesn't get ambushed by unplanned expenses.

"Murphy's Law" seems absolute and things always happen at the least opportune and convenient moment. Having a fund started really helps defray the affects of that,....

Good luck!!!!

Mike W

Steve, How important is it to change the oil after techron is added? I added techron at the time of the oil service (about 75 miles ago). Do i have to change the filters again (also new)? Will there be a potential problem if I don't chasnge the oil. Obviously I would like to avoid doing it 2x. Also what grade do you reccomend for south florida. thanks, Mike W

Steve Weiner-Rennsport Systems

Hi Mike:

If you simply put in one bottle of Techron, you can just wait for your next 3000 miles oil change. I try to time the Techron treatments just before doing that so the byproducts of combustion that the solvents loosened up can be flushed out.

I'd use Mobil 1 15w-50 in your engine.

Gary Perry

Steve, the only gasoline I use is Chevron, which has techron in the gas formulation. I have seen a lot of posts that recommend adding a bottle of Techron to the tank periodically, but if you use only Chevron gasoline is that still a valid recommendation?

Mike W

thanks Steve. Glad I won't have to change again. I don't know if you remember but you were of so much help, talking to me while I was looking at a car in NJ a couple of weeks ago(which I now own). I called and you were so generous with your time you helped me make sure the car was right. Just want to say thanks again. Mike W