Here's an unpdate for those of you who have been following the saga of me trying to get to the bottom of one sided sooty tailpipe on my 10,000 mile 997s. The engine was in tolerance for compression and leakdown and passed the full diagnostics but, after speaking to Porsche, the dealer has removed the engine and has started to tear it down. So far, they have found oil in the exhaust port of number 4 cylinder and are going on to check the bore tomorrow. Number 4 is on the side that supplies the sooted up exhaust so looks like we may have an explanation. Not sure what Porsche intend to do about it yet but both dealer and Porsche have been brilliant - something I hope will continue.
Will let you know the final outcome.
PS taking the opportunity to fit a PSE and new clutch.

 

I have been following this saga with interest. I have suggested a couple of times that both a wet and a dry compression test be carried out. A wet test requires a squirt of oil through the spark plug hole and reduces leakage past the rings. A low dry pressure which increases when wet indicates a problem with the piston rings/bore but a low dry pressure that fails to increase when wet probably indicates a valve seating problem.

 

Mark - interesting that Porsche is allowing the dealer to do the teardown... thanks for the update!

You need a clutch already? <g>

-don

 

Excellent news Porsche and your dealer are cooperating to this extent! I had a feeling standard compression/leakdown tests would not be enough to reveal the cause. It's going to be interesting to see what develops...please keep us posted and best of luck.

 

his compression wasnt low to begin with a a wet test wouldnt have made much diffrence. then there is always the problem with wet compression tests on a flat motor..................

 

Thanks for keeping us posted...I know there have been a number of drivers on various forums (fora?) that have reported the same uni-soot problem.
Nice job on adding the PSE....you deserve a treat after this saga!

 

Thanks for the update Mark. There must be oil burning off in at least one of the right bank of cylinders. Question is why. What was your oil consumption just prior to this intervention and was it worsening or constant? Gerry

 

I was using about 750mls per 1000 miles but suspect it was being burnt in the right bank only - and probably cylinder 4 from what we know so far. If anything it was lessening as the engine bedded in.
The new clutch is a precautionary change as I bought the car second hand - if the existing one looks great I'll leave it in, but it's not a lot of money to pop a new one in while the engine is out. And if I end up with a new engine under warranty it could come with a new clutch (they often do evidently according to my dealer). Porsche Bristol sold me the car and are really going the extra mile - but so they should given how much a 2 year old 997 costs over here!

 

Mark

Glad that its getting sorted but meanwhile does the dealer supply you with a car to drive around while yours in the workshop?

 

Re oil burning in one cylinder: this would seem to be the case but my tech reportedly found no evidence of this when he compared sparkplugs You might expect to find fouling or at least a 'sooty' plug We shall see.

 

I wouldn't expect much there! My dealership has provided me with a Kia Minivan and a base model Hyundai - both of which were Enterprise rental cars in bad shape. Kinda annoying after you hand them your keys to your $124,000 car (after TT&L). My sales taxes were more than the last car they gave me!

 

I'm thinking the same thing here. How long has your car been in the shop for and what do they have you driving? In some states extended time in the shop qualifies for the lemon law. I'm glad the dealer and Porsche is trying to get to the bottom of this for you, but you own a $100k car, you should be driving it, not watching it get disassembled.

I'd settle for driving nothing less than an equivalent car while it's in the shop. If you had a "problem" with cash flow in a given month you think Porsche would be ok with taking a "lesser payment"? You shouldn't be ok driving a lesser car.

 

What year is the car and how many miles on it?

 

Yes a good point, and on reflection oil in the exhaust port would suggest a leak via the valve stem, something a compression test would not pick up.

 

These engines are known for "leaking" small amts of oil down valve seals. This is why you will characteristically see a small puff of smoke on cold start when engine has been sitting. Probably made worse by use of a 0 wt oil which is thinner than water at normal temps. But they already know this. Something else going on here?