I was wondering if I could ask the list for some advice on a problem
with my '72 Mk IV. I have been reading the list for a few weeks now and
I see there are some very mechanically knowledgeable folks here.
The engine on this car starts fine, and runs ok up to about 3K rpm when
cold. Above that speed it starts to knock. As time goes on, and it
heats up, the speed at which it starts to knock drops to about 2K rpm.
This is not a subtle sound, but loud, a metal on metal sound. It is not
pinging or pre-ignition. My limited experience with a similar sound was
with a motorcycle with piston slap. This engine burns no oil. I
replaced the timing chain, tensioner, thrust washers, and rear main
bearing. No change. I looked for play in rod bearings but this was not
easy to do from under the car. During coasting or heavy acceleration
the knocking is almost eliminated except at over 3500 rpm. The engine
has about 37K miles on it and shows evidence of a fairly recent (in
miles not time) overhaul. The car sat inside from 1992 until I bought
it.
Any thoughts or comments are welcome. Any tests I can do to try to pin
this down short of a complete tear down?
BTW thanks to the folks who answered my earlier request for rear axle
sources for my Mk III. We're still working on that too.
Thanks in advance,
Steve Keidl
1969 Mk III - Unsafe at any speed
1972 Mk IV - Work in progress
|