From: Wally Plumley [wplumley@bellsouth.net]
Sent: Monday, January 22, 2001 8:49 AM
To: 928
Subject: [928] Re: More Timing Belt Questions

At 12:04 AM 1/22/01, Brian Strohmeier wrote:
>I feel a little stupid asking this question, but do 928s have one or two
>timing belts?


USA 928s have one toothed timing belt. Starting in 1985, they also have two 
small timing chains.

>In any case, I wanted a few opinions on my own timing belt situation (I'm
>the 4th owner, having bought the car in 1998 with 38,000 miles).  The second
>owner had the timing belt, adjusters, and the water pump replaced in 1993
>when the car had 30,000 miles on it.  The second owner had the car from
>1996-1998 and only put 1,000 miles on it without doing any maintenance
>except an oil change.  I had the timing belt adjusted in 1999 when the
>mileage was 45,000.  The car now has 51,000 miles.  Going with the 15,000
>mile timing belt adjustment schedule, the car will need a timing belt
>adjuistment at 60,000 miles, which I should reach later this year.  At this
>point, the timing belt will have only 30,000 miles total.  Should I keep
>going to 75,000 miles before changing the belt/water pump or would you guys
>go for the change at 60,000 miles?  I've read in several 928 articles that
>the first timing belt change doesn't need to be done until 60,000 miles, but
>that age should also be taken into account, not just mileage.  What do some
>of you experts out there think?


There are two answers to these questions - the official Porsche answer from 
the maintenance book; and opinion, whether informed or uninformed.

Official Porsche answer (from the Warranty and Maintenance Booklet for a 
1990 GT)
Every 30,000 miles - Check Drive Belt Tension; Check oil level in Tensioner
Every 60,000 miles - Replace Camshaft Drive Belt. Check tension after 2000 
- 2500 miles.

This schedule is no doubt the source of the Urban Legend, prevalent among 
Porsche mechanics, that the 928 camshaft drive belt doesn't require adjustment.
It is also interesting that Porsche requires checking the tension after 
belt replacement, but not for a new 928. Did the factory run the engine 
long enough to break the belt in, then check the tension?

Opinion
Every 12 months or 12,500 miles - Check oil level in Tensioner
Every 24 months or 25,000 miles - Check Drive Belt Tension
Every 60 months or 50,000 miles - Replace Camshaft Drive Belt. Check 
tension after 1500/2000 miles.


You will get a LOT of opinions on this one. In fact, David may disagree 
with my opinions, and his opinions, not mine, should be considered as 928 
Specialists' official position.

Wally Plumley
928 Specialists