Re: Thermostat/Oil Cooler (long... but maybe useful...)

["Dave Campen" <dave@campen.eurobell.co.uk>]

----- Original Message -----
From: Jim Adney <jadney@vwtype3.org>
> I don't remember for sure either. I don't see why a long warm-up
> period would make a head crack. I'm just convinced that the
> warmup period is a time of high wear rates on things like pistons,
> cylinders, rings, and bearings, because of poor clearances when
> cold and poor lubrication from oil that is still too thick.
>

The way I've always understood it, one cause of head cracking is not
allowing the engine to warm up gently. If you drive the car hard when cold,
not only is there the drastic piston/cylinder wear that Leon mentioned, but
there is a huge temperature differential between the hot combustion gasses
and the old head. The gasses are a little cooler if the car is driven
sympathetically, and the head can expand at a more natural rate. Think of
the thermal shock when you take a plate out of the oven and rinse it with
cold water. Crack......

I'm no metallurgist, so this may be complete rubbish. It's just what I was
told when I first got into Veedubs.


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