The heater valve I bought from Brickboard sponsor FCPGroton is a metal unit, not plastic, like the Volvo original.

Presumably this will avoid the catastropic coolant loss failure of the plastic units.

While replacing mine, I briefly considered hoe to inject "stop Leak" just into the heater core and not into the engine block.

With the heat control valve and/or the hoses removed it is easy enough to rig some connection to the inlet/outlet pipes of the heater core at the firewall.

I couldn't figure out what to use to pump hot water and the stop leak into it, so, I didn't bother.

With the hoses removed, I did give the core a good back-flushing, however.
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1989 740Ti 1986 240DL 1984 244GL