The water valve may gone into an 'off' mode. If the vacuum diaphram in it has a hole, it won't allow hot water to get to the core.
The vsv with it may be bad. Check to see if the valve works. By-pass the vsv with the vacuum hose hooked directly to the heater water valve. (its on the firewall, heater water hoses hook into it).
The vsv goes bad with age. I just removed mine, and run vacuum to the water valve in the fall/winter/early spring. Then I remove it and plug a golf tee into the vacuum line for the late spring/summer.
|