Re:1982 GTV-6: cooling system/cylinder head

[Gerry Lehmann <lehmann@domain.elided>]

Richard, Alan's suggestion regarding blockage is certainly a
possibility.  I would also offer the possibility that you have a bad
pressure seal somewhere in the system, most likely at the cap/bottle
interface.  I had a similar phenomenon occur where the bad seal at that
point would simply let go as the system got hot and pressure reached a
pound or two.  The exhibition of the process was much like what one
would expect from taking the cap off of a hot engine. the coolant would
rise quickly as the pressure dropped below the temperature/pressure
vaporization threshold. 

Took me quite a while to figure out because once the pressure released
(burped to below a couple pounds) it would seal again. Subsequent
removal of the cap would release the last pound of pressure and make it
seem like the cap was holding. Surprised me when I realized how little
the system must actually require operation at higher pressure.

Hard to tell for certain from the description but I would suggest a
pressure test of both the system and the cap and a good inspection of
the interface.   The finishing of the seat on the bottles I've purchased
over the years has never been what one would call precise. Its an easy
fix if that's what it turns out to be.

Gerry Lehmann
'86 GTV6

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