[s-cars] Re: Hoffman Audi Responds.. (burned valved - visually apparent).
thecyberpoet at cyberpoet.net
Wed Jan 1 02:33:08 EST 2003
One thought on this message...
First, let me say that I've never seen an Audi with the problem I am
about to describe, but have seen it happen to a number of Saturn SC2's
(1991 - 1997) and the culprit might just be the same (although I won't
put any money on it -- it's just food for thought). Second, let me say
that I haven't seen the rest of this story previously, have recently
rejoined the list after a couple years off...
Saturn's SC2 engine is a straight four with dual overhead cams. If
driven hard consistently, it is not uncommon for one of the stock
factory cams (the exhaust cam in particular) to torque itself over time
(as little as 12k to 15k miles, more often in 60k miles), so that the
rear part of the cam is actually permanently twisted from where it
should be (by design) by comparison to the front of the cam. This in
turn, leads to the rear one or two exhaust valves not sealing
themselves when they should, and in turn causes them to burn (as well
as a number of other symptoms, such as high oil consumption). If left
unattended, it can cause unexpected metal fatigue failure, but
consuming a liter of oil every 400 to 1000 miles is usually enough of a
head's up to get the owner to take the car in... Once the valve cover
is off, you can spot the bad valves in such a situation visually
without any problems because of their discoloration and the combustion
by-products on the valve seat area around it -- you don't have to yank
the head to see it.
Somehow, I doubt that Audi ever used inferior metals in their cams, but
there is always the possibility that you somehow got a
less-than-optimal one. It is possible for a mechanic (or even lay
person) to spot valves that have been victims of bad-closure times
Good Luck, and happy New Year!
=-= Marc Glasgow
On Tuesday, December 31, 2002, at 12:00 PM,
s-car-list-request at audifans.com wrote:
> When last I saw the head, and when their technician was explaining how
> he knew it was the two valves (he could tell just by looking, he said),
> the head was assembled. How in the world can Sam Pines of Hoffman Audi
> know that the head is straight, that there are no cracks in the head,
> no problems with the valve guides or tappet buckets, and that no other
> valves are damaged without disassembling the head? Additionally, that
> head was not taken to any machine shop, unless done after Hoffman was
> forbidden in writing from proceeding.
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