[928uk] Thrust Bearing Failure

[Paul R Smith]

TBF is caused when the pressure from the flex plate exceeds the film 
strength of the oil, so thin oil makes it more likely. If the engine had 
10W-40 in it, did they chose that, or did you?
Did they check the thrust bearing clearance, or just release the 
flexplate pre-load?
Did you ever ask them to check the clearance? (This is where a 928 
specialist is going to know what to do, but a "porsche specialist" 
probably won't.)

A loose pinch bolt certainly suggests shoddy work, but didn't cause the 
failure.

Cam sprockets wear. They will wear faster if the belt is over-tensioned 
or loose. Was the belt tension checked, or just a guess based on the 
wear. It the tension was checked, there should be a figure quoted.

ATF is an acceptable substitute for gear oil "if the correct grade is 
not available", so ATF in the diff implies extreme laziness or incompetence.

I would suggest finding a few articles on flexplate TB checking, print 
them out and show them to the garage. This will show them that it is 
common knowledge amongst specialists that it is important to check the 
TB clearance.
When they have had time to absorb that, point out how much money you 
have paid them over the years, and ask them if they would like to make a 
contribution to the repair replacement of your engine.

If you went to court, you would have a very difficult time proving that 
anything they did caused the TBF or that anything they didn't do could 
have been expected to have been done.

Smiffy


On 20/02/2012 6:19 a.m., go928 wrote:
>
> Late last year my S4 auto suffered terminal tbf - the engine is 
> probably a write-off.
>
> Briefly, I've owned the car about 10 years, covering about 6,000 miles 
> a year.  She has 130k on the clock.  Throughout the last 10 years she 
> has been maintained and serviced annually by the same firm and a flex 
> plate check has been specified at each service.  Over the last couple 
> of years I have had a series of problems with difficulty starting, 
> stalling and uneven running.  She has been back to the specialist on a 
> number of occasions and fuel pump, MAF and ISV among other things have 
> all been replaced.  Each time the immediate problem has been resolved, 
> but the car was not running quite right, although it was hard to say 
> precisely why.  I now suspect this was early symptoms of the pending 
> failure.
>
> My view is that the Porsche specialists who look after the car should 
> bear some responsibility, but they do not agree and have washed their 
> hands of my situation.  Maybe I am not being as objective as I should 
> be so I would welcome any thoughts.
>
> My reasons for blaming the firm who looked after the car are:
>
>     * Everything I have read about tbf seems to suggest it is unheard
>       of where the flex plate has been checked and released regularly.
>     * The engine finally seized only about 2,000 miles after the last
>       service/flex plate check.
>     * When the tbf was diagnosed (by a different firm) the pinch bolt
>       was only finger tight.
>     * The firm admit that they do not change the pinch bolt when they
>       check the flex plate.
>     * The cam belt rollers are damaged due to overtensioning of the
>       belt.  (As they have changed the cambelt twice since I acquired
>       the car, to my mind, even if they didn't cause the damage they
>       should have spotted it and changed the rollers).
>     * ATF in the diff.
>
> The last two points have no direct bearing (ha ha) on the thrust 
> bearing failure, but do indicate a questionable level of care.
>
> My questions:
>
>     * Is it fair to pursue the firm for a contribution towards the
>       cost or should I accept (as they claim) that the thrust bearing
>       can fail at any time, even if the flex plate is regularly checked?
>     * If I do have a claim, any thoughts on how best to get them to do
>       the decent thing?  I will take them to court if necessary but
>       would prefer to avoid all the hassle if possible.
>
> Thanks in advance.
>
> Graham
> (91 S4 auto)
>
>
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