Rear heat odd behavior

[robinasu]

The summary is the rear heater core heats due to coolant flow when the rear heat switch is OFF, and cools down when the rear heat switch is on. I verified this by removing/attaching the output from the solenoid valve to the 2-way valve. I'm a little confused. It shouldn't matter in which orientation the 2-way valve is connected. I believe vacuum should allow coolant flow, but it doesn't. When I disconnect vacuum, the rear core heats. I'm wondering if somebody hooked up the 6 port valve incorrectly? I don't see how that would do it, but I can't find a great diagram.

Any ideas??

[chevymaher]

Sounds like it isn't getting good flow but has flow all the time. Water valve is fried and stuck partially open toward the closed side.

[dramey]

I did away with the water valves on my van.

[robinasu]

I did away with the water valves on my van.

Full flow all the time?

[WoodButcher]

Robin, a lot of us use ball valves from the plumbing supply. Mounted in a convenient location you never need to worry about that craptastic plastic breaking again and in the summer when running the AC you don't have warm water in the heater core. Every little bit helps in the hotter climates. Search Lumpy's threads for "heater core bypass".

[dramey]

I did away with the water valves on my van.

Full flow all the time?

Yes. Most cars of the 50s and 60s and a lot of the 70s didn't have water valves. Just turn the heater control to off or any other position beside floor or defrost.

[chevymaher]

The heater coil may be clogged or the hoses are run incorrectly. Back flush the rear unit to knock the crap inside it out.

[robinasu]

Well, if for sure gets super hot when in the off setting, that's for sure. I have yet to find a clear diagram of the exact hose connections. Will keep searching.