Strange Vibration? - V8 engine vibrates at 1800rpm

J

JohnGlinn(Cardiff)

New Member
The same gentleman with the VIP who has a problem with his aircon (see earlier posting) demonstrated the phenomenon in the above title.
With the car at rest and the engine idling, no problem, increase the revs to 1800 and a vibration occurs within the engine (no real noise, just a shaking) increase to 2000rpm and it disappears - ANY IDEAS?
Regards, John.
 
JohnGlinn(Cardiff&District) said:
With the car at rest and the engine idling, no problem, increase the revs to 1800 and a vibration occurs within the engine (no real noise, just a shaking) increase to 2000rpm and it disappears - ANY IDEAS?
Regards, John.
Click to expand...
It may be worth checking the cooling fan still has its balance weight fitted.

I had a similar problem and noticed mine was missing (just a piece of metal folded and spot welded around the edge of one of the fan blades).
One second-hand fan later and the vibration had gone, though the vibration had also affected the water pump bearing so I had to replace the water pump too!
 
hi,
on the air-con cars, it runs a viscous coupling and a 13 blade plastic fan, not like the standard V8 with a belt driven 5 blade steel fan.
 
JohnGlinn(Cardiff&District) said:
Peter and Ian,
Does this mean that there is no balance weight on the air con cars?
Regards, John.
Click to expand...
Hi
Ah!, I think the air-con cars had a plastic fan, like SD1's. Therefore no balance weight.
A vibration can however be caused by any reciprocating part, such as an askew alternator fan guard.
I had a SD1 Vitesse where the circular flat guard on the alternator came adrift and was thrown to one side, up against the pulley. A fantastic vibration then became apparent.
 
hi,
that's right john, no balance weight on the plastic fan. which is a 13 blade one as a matter of interest.
:D
 
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