The Stovebolt Site Forums The Shop Area General Truck Talk Was this a Chevrolet part?

Does this heater shut-off valve look like something installed by the factory, dealer or by the p.o.? Did the basic round-core heater have a shut-off?
Shut-Off Valve Picture

Those were an aftermarket item. It could have been installed by the dealer or anyone for that fact. Heaters were a dealer installed option for many years. I don't know the year that heaters finally became a standard factory installed item.

Thanks Tiny.

I don't know for sure, but I'd love to find one of those.

I thought that they were available and sold as a Chevrolet Accessory? I know that they were sold by FLAPS also.

For 1935-1939 the heater shut off valve had a hex nut/bolt with a ball on the end that turned in to shut it off instead of the wing nut that was used 1940-up. GM part #985079. I use mine in the summer to shut off the water to the heater. They were dealer accessories and aftermarket products. They were used on both the cars and trucks. I've seen them on the water pumps, and the thermostat housing. Does anyone know exactly where they go?

Here you go.

I don't know if there's an "official" mounting spot but I put mine on the pump. That way the pressure is off of the heater core when I have it shut down. If you mount it on the thermostat housing the core is pressurized whenever the engine is running. Most times it won't make a difference but if there's a weak spot in your core.....

You have it backwards Tony. The pressure comes from the below the therm. & returns to the water pump.
I believe those or similar are still available from the aftermarket.

Heaven knows I'm wrong my share of the time but..... ....it looks like the pressure side is off of the pump to me.

The photo in my first post is where the valve was located prior to restoration. I have no reason to believe it was not the original location as this was a very original and complete truck.

Tiny, the cooling system diagram you linked to shows the water flowing from the radiator to the water pump, i.e. inlet/suction. After it flows through the engine it exits at the thermostat, i.e. pressure side. (the actual pressure side of the pump is the outlet mated to the block)

The pump is pushing the water. While it pushes the water through the engine it also is pushing it through the heater hose. The pressure will be highest closest to the pump rather than after traveling through restrictions of all of the internal passages will it not? The suction is on the inlet side. The outlet to the heater is on the exit side of the impeller.

On further reflection I believe you guys are right and I'm wrong. Can someone pass the salt & pepper, I think I have some crow to eat.

Sooooo, the hottest coolant is coming from the thermostat housing, going back through the radiator and cooling off. The pressure is created from the pump. The pressure is the lowest going to the pump. The heater hose inlet and lower radiator hose inlet on the pump are directing the coolest coolant back to the pump. With that, I would assume, the heater control valve goes on the thermostat housing. Shutting off the hottest and more pressurized side of the system. But then, I don't run a pressurized cap on the radiator either. Sigh!!!

Growing up I'd see them used more to by pass the leaking heater core....as best I can remember. I think you can still get one at a local FLAPS store...or they can order you one with free shipping.

My 37 has a similar shutoff and since it had a Arvin heater its probably aftermarket.

They never were any good. They would either freeze up or leak.