I'm replacing the rear heater core and heater valve in my vanagon,
can anyone tell me can I do this without draining my entire cooling
system? If so I plan to clamp off in & out hoses and replace core. I
assume the white plastic screw is a bleeder valve, how long do you think
it takes to bleed system, and should I also bleed from the radiator
bleeder valve?

thanks in advance,
Joe F.
'87 Vanagon Syncro
"The White Whale"