Yes, the plastic housings do crack, around the bolt holes and into the oring
area. I've seen several do this.

Karl M

----- Original Message -----
From: Tim Marciniak <tmarcini@mail.execpc.com>

> I located a coolant leak coming from the thermostat housing area.  I
> replaced the O ring that seals the lower thermostat housing to the front
of
> the left head.  I could not get a real good look at the seat in the
> thermostat housing that the O ring sits in but I did try to clean it out
as
> best I could.  I reassembled everything, also did my annual cooling system
> flush etc etc and was a little dissappointed today to see that I did not
> fix the small coolant leak I had originally set out to fix.
>
> I am now suspecting the lower thermostat housing and thinking that there
is
> a problem in the seat for this O ring. The thermostat housing is plastic
> and like other plastic parts it tend to degrade by cracking I presume from
> the heat and cooling cycles.