As a temporary, roadside fix, I bypassed the valve entirely. To do this, take the hose that goes from the engine (on the drivers' side manifold) to the valve. Disconnect it at the valve end. Now disconnect the heater hose that goes from the water pump (on the drivers' side near the fan belt pully) and tuck it out of the way somewhere. Take the loose end of the manifold/valve hose and attach it to the water pump. You've now bypassed the valve. This is what the system looks like before you've done anything. The view is standing over the driver's side (LHD) fender, looking into the engine compartment:
After the bypass, Hose "A" and Hose "C" will not be connected to anything, and Hose B will go to the water pump instead of the valve.
