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Re: TQC Piston Failure

>   I have a quick question/heads up for turbo owners.  Recently I was
>experiencing some oil consumption, boost inconsistancies and high pressure
>in my crank case.  A compression test checked out and I decide to take off
>the head, spruce it up and replace a supect gasket. 
>   It turns out that the # 5 piston was setting up to self destruct!  In
>the area between the oil ring and the next (compression?) ring, the 1/8
>inch surface area of the piston had begun to seprate from from the piston. 
>A total of about 4 pieces, all about 1/8-1/16 long, and the depth of the
>ring cut  were seperated fron the piston and free floating between the
>rings!  Luckier still was that one of the rings had broken but not yet
>fallen out and kept the pieces between the skirt and the piston (all pieces
>present and accounted for). 
>   Incredibly, the bore is clean with no scoring and no measurable signs of
>taper or wear, i think new regular size piston will do the trick, luckily
>no bad signs higher boost on the other pistons.  I have seen melted,
>detonated and banged pistons, but never this failure mode, any ideas?. 
>Better on the bench than the road I guess.  Another Audi repair set to
>really exceed the estimate! 

Actually, I know of a case where there was failure of a piston, I think #5,
due to metal filings or such plugging up the oil channel(s).  Don't know if
that would casue the faliuire scenario described, though.

Of course, this was found after under 20K miles and Audi replaced the
offended and abused motion generating unit under warranty.  Bet you're past
that point!!

Stephen A. Marinello, Ph.D.
Corporate Technical Services
Newpark Resources, Inc.
P.O. Box 6411 - Metairie, LA 70009
504/838-8222      FAX 504/833-9506