[s-cars] Potential connection between bent valves and subsequent rod bearing failure?

[Joe Pizzimenti]

Sounds like the valve hitting the piston, which will inevitably hurt
the rod bearing.  He could try to plastigauge a new bearing in, but it
would be best to pull the motor & check everything.



On 5/16/09, David Forgie <forgied at shaw.ca> wrote:
> We all know that if the timing belt breaks, there will be bent valves
> (typically intake valves) because
> the AAN is an "interference" engine.  Several of us have been trying to help
> diagnose a knocking
> noise in a new UrS4 owners car on AudiWorld.  The owner insisted it was
> coming from the head but
>  we were skeptical.  At the suggestion of one poster, the owner bought an
> automotive stethoscope
>  from Harbour Freight and after he got it, he pin-pointed the knock to low
> in the block.  He dropped
> the oil pan (no small job on an AAN in the subframe) and discovered that one
> of the rod bearings
> was gone/in pieces (in the pan).  I asked him which cylinder and he replied:
> "Cylinder 3. So far I
> have burned a valve, then bent two valves and now disintegrated a bearing,
> all in that cylinder."
>
> I can't help him with the burnt valve, but I am wondering if the bent valves
> came from a timing belt
>  "issue", it could mean that the force of the piston hitting the valves,
> which would have been
>  transmitted to the crank, via the rod and the rod bearing, may have been
> enough to damage the rod
> bearings.
>
> Does that seem possible?  It's the only co-relation I can think of but it
> might not be valid.
>
> Dave F.
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