My experience with these valves (and on my '84 the same type of valve is
used on the front heater) is that they wear and shrink internally and
don't completely shut off the flow of hot water to the core.  I have
replaced the one in front, but last time I checked the one on the rear
was not available separately from the core. $$$$$$ I hope that is no
longer the case, replacing it is the only fix unless you use a C-clamp
to pinch off the hose in the summer!
--
Stuart MacMillan
Manager, Case Program
800-909-8244 ext 208

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