Recent motor melt down

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <199801300917.BAA23286@lambda.ben2.ucla.edu> Michael Williams writes:

> Speaking of timing belts.  My friend is insisting to me that all 
> manufacturers, namely benz and porsche recommend that you replace the 
> timing belts every 30k miles..I insist that i know that the recommended 
> change interval is 60k...who is right? i think i amsince everything on 
> this list has always been 60k and in every ad and book that i have read 
> it is the same....

I hear different stories from different people.  I think the manufacturers are 
reluctant to go public for a number of reasons - implied warranties being one.
 
Personally, I regard 60k as a "do not pass" upper limit - I'm happier with 45k 
on my own vehicles.  I understand that Ferrari recommend 30k on at least one 
car (350GT?) and it's an engine-out job.

However - age is a factor as well as miles.  The S1 timing belt that broke so 
disastrously at Goodwood in 1996 had only done a few dozen miles - but it was 
13 years old.

As far as the V8 is concerned, I refer the interested reader to: "Design and 
Development of the new Audi 3.6 litre, 32 valve V8 Engine" - Johannes 
Steinwart, Armin Bauder and Gerd Ohrnberger.  The copy I have (thanks to Scott 
Mockry) is a friend of a photocopy of a reprint from an SAE paper.  Page 114 
states: "A width of 20mm was chosen to ensure that the belt will last the life 
of the engine."
 
Of course, it's entirely possible that something else has gone (e.g., the 
hydraulic tensioner) and not the belt.  Only removing the cover will tell. 

-- 
 Phil Payne
 Committee Member, UK Audi [ur-]quattro Owners Club