I posted the story of how I came to own a 1988 911 with only 6800 miles on it in
the spring of 1997. Since buying the car I have had tons of fun and, for the
most part, my experience owning a Porsche has been nothing but pure joy.
However, there have been problems. The largest of
which is disclosed here in the sad saga of premature valve guide wear…
Here’s the story so far.
On Thursday, June 19, 1997 I sent the following message
to the Porschefans Mailing List:
Ugh. When I bought my ‘88 Coupe about a month ago it had 6800 miles on it. The dealer, as part of the purchase did a valve job just to ensure everything was up to snuff (and because I complained that I thought I heard valve noise during my test drives). The valve noise was not cured by the original job and this week the dealer agreed to do the job again (assuming they had missed a valve or something).
They did the work today, and claim that the valves are adjusted as they should be. They claim that my valve guides look worn. This car now has only 8400 miles on it!!! How could this be?!?!?
The service manager’s suggestion is that I just drive it like this for a while and eventually get a top-end job done (~$2000!!! Eeeeek! My wife’s gonna kill me!).
Questions I asked, and answers I received:
Q: Will they get worse (I think the noise has gotten worse since I’ve owned the car)?
Q: When do I know I really need the top end job done?
When the valves get REALLY noisy?
A: I don’t have a good answer for you. Sorry.
Q: If they get worse, will they cause more damage
(making a top-end job even more expensive or even ruining the engine)?
Q: What should I do?
really don’t know. You need a top-end job.
Q: But the car only has 8400 miles on it!?!?
A: I know, I’ve never seen anything like this.
This bites. Does anyone have any opinions (stupid
question for this list ) on what I should do? I don’t
remember reading anything in the 1000s of pages I’ve read about 911s where this
era of car had any sort of chronic valve guide problem.
What could have caused the guides to wear like this?
I got several good responses, including the (apparently
canned) response from Bruce Anderson:
The oil consumption specified by Porsche for the Carrera
3.2 engines is 1.5 liters per 1000 Km (or approximately 1.6 quarts per 620
miles). I consider this to be excessive, so your 3 quarts per 1,000 miles is
completely out of hand.
Over the past decade there have been a number of
different theories on why the intake valve guides and/or valve stems are wearing
out on the Carrera 3.2 engines, we never saw the earlier 911 engines with intake
valve or valve guide problems. The latest theory, offered by a couple of my
friends; Ted Robinson of German Precision and Dwight Mitchell of Autosport
Technology is that the wear is caused by the Viton valve stem seals used on
these engines. The theory is that they work too well and prevent the guides from
getting adequate lubrication causing the intake valves and guides to prematurely
wear out. Usually sometime between 40,000 miles and 60,000 miles this wear shows
up and by then the valve stems seals themselves have also worn out and the
engines will have excessive oil consumption, plug fouling and all the rest.
Usually a good indication of worn valve guides is noisy
valves, the valves should be quiet on a 911 after they have been adjusted. If
the valves are noisy you should have your mechanic check the valves for valve
guide wear. You can check the valve guide wear by pushing the valves from side
to side with a screw driver with the valve just lifted off of the seat a few
millimeters (about 10 mm). You can actually judge how worn the guides are with
From this I gleaned that some 3.2 liter Carrera’s have
been seen with premature valve guide wear, but usually at around 40,000 miles or
so. Nobody has ever seen this problem on a car as "young" as mine.
I went to the dealer and asked them what they could do
to help me. I told them that I felt that Porsche and/or the dealer should pay
for at least part of the repair cost (which was now estimated to be around
$3500!). The dealer said they would cover 30%. To me this meant that they would
simply not make a profit. So I wrote a nice letter to Porsche Cars of North
America. I explained my situation, including an exerpt from Bruce Anderson’s
email. Soon I received a reply telling me that they valued me as a Porsche
customer and the dealer had their full authority to "take care of me".
With this letter in hand I returned to my dealer and was told that together
Porsche and the dealer would cover 60% of the cost. This, I could live with.
I mean, it’s not like the car is still under warrantee.
It is 10 years old and Porsche certainly had no technical obligation to pay for
the repair. But there is clearly a problem that could be only caused by a defect
in workmanship or materials. So I took them up on their offer.
I dropped the car off on November 12 (I waited until the
weather around Seattle was supposed to turn bad…as it turns out we had a
beautiful stretch. Sigh.) The service manager said it would take about 10 days.
I asked the service manager to call me when they had the car disassembled so I
could come in and check it out. When they called and I went in I took a bunch of pictures with my digital camera. The heads had already been sent off
for work so I couldn’t see them (or the valve guides) but I was able to see the
rest of the engine and transmission in it’s disassembled state. Cool.
As I expected the mechanic found a few other things that
"needed work". For example, he felt that it would be a good idea to
replace an oil return hose. He also noted that there was a service bulletin on
the G50 transmission. Apparently the shaft for the "throwout fork"
(see image 14) had a
poor bearing design. The service bulletin calls for machining in a new bearing
race in the lateral shaft, and this can greatly improve the life of the clutch.
Since my clutch only has about 11k miles on it now, I figure the cost of the
parts (he’s not charging me labor) is worth it. Another item that he fixed was
the cylinder head temperature sensor; it was upgraded to the two wire design
(the original was a single wire unit that got ground from the cylinder head and
was known to be unreliable).
I got the car back on Saturday, December 6, 1997. I had
to pay about $1700. This included 4 intake valves, all 12 valve guides, the
clutch update, etc… This was 40% of the total cost. Porsche and the dealer
paid the other 60%.
The ticking is gone and the motor feels like new. The
clutch feels smoother. I’m completely satisfied and excited to have my car