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.

The other thing I realized today after studying my parts diagram is that
when I removed the lower thermostat housing there were no washers on the
two bolts that secure the housing to the head.    The heads were redone
about  6 monthes ago and I'm thinking that maybe the mechanic that did the
work did not use lock washers when he assembled it.  If that the case I
suspect that one of the bolts could also be bottoming out thus causing the
thermostat housing not to be drawn up tight against the head.

Anyways getting back to my original question--How long does this plastic
thermostat housing last--is this a part commonly replaced.

Tim Marcinial
90 Multivan