The Stovebolt Site Forums The Shop Area Engine Shop coolant shut off valve?

There's a valve that can be turned on and off by the water pump, leading to the radiator. I was wondering if any of you guys might now which position(up or down) is open or closed, and if I should have it open or closed. ?????????

Leave it open better cooling that way also if it is a ball valve with a lever the lever is direction of flow. If in doubt warm her up and put your hand on the heater box T/C Steve

Thanks. It's got a lever on it and I don't have anyway of telling which was open or closed. I'll see about the heater box though.

OH, correction, it's not leading to the radiator! Don't know why I said radiator though. It's to the heater.

In a way you were right anyway. A heater is just a small radiator. As for on or off there are two trains of thought. One is to leave it on for the additional cooling it provides the engine although that puts more heat in the passenger compartment. The other is to put the valve on the "feed" side and shut it off during the summer. That helps keep heat out of the cab AND keeps pressure off of the heater core. It all depends on personal tastes and there is no "wrong" answer.

When I said "on or off" I meant should the valve be on or off, but not off of the engine. Thanks for the help, I messed with it and turned it both up and down and when I pulled it up it let in the coolant since the hose was warm so I figured that one out.

Leave it off. That is an old trick they used to use when the heater valve would fail. open - heat - - closed - no heat

54tow, it's not just that. It's also just in case your heater core ruptures. It could just be a safety precaution.

Doesn't matter where you mount the shut-off valve - either intake or outlet of the heater.
If the valve is turned off, there is no flow through the heater hoses either way.

The purpose of this valve makes sense especially for hot summers.
During the hotter months, you want to turn it off, so all the coolant can flow through the radiator for vital cooling.
If you leave the valve on, a portion of hot coolant bypasses the radiator at all times and will just return to the block uncooled.
The small heater core does get hot, however never removes enough heat to cool an engine and certainly doesn't help in keeping the cab cool.
Don't know how hot your summers get, but in the desert you take as much cooling as you can get and a valve can help.

AD trucks had an automatic heater valve that was installed inside the cab on the fire wall.
It measures the internal cab temperature and turns the heater valve on and off automatically ... a 'cool' accessory indeed.

Oh, if that's the case, I'll leave it off. I thought that it would keep the engine from getting more coolant for some odd reason, so I'll just leave it off for now.

To put the valve on the "feed" side keeps coolant from going to the heater core which is good if the heater core leaks.....which you will want to find out one day!
It will help the engine to run a little cooler if it circulates but I'm not sure how much cooler. What that does is give the water a "longer" route to flow and cool off some and the heater core will disipate some heat if that is the intent during a lot summer if the engine starts to overheat.
BUT if you want to stop the water flow all together due to a bad core some folks just take the ONE hose and make a "loop" to where the coolant comes out and then right back in without using a valve or even going to the core.

Well, for the little bit that it ran before I ran into fuel problems(gas not wanting to go from can to carb) it didn't leak any, so that is a good sign.

I think there is some "mis-information" here... the valve only stops the flow of coolant. But because the other heater hose does not have a valve, the heater core is always under pressue. So if the core leaks or ruptures, this wil not stop the coolant from leaking out.

Just thought I should clear up that point.

Gotta disagree. If it's on the "pull" side of the pump & turned off the pump is putting pressure on the heater core all the time even when no fluid is moving. If the valve is on the "push" side & turned off the heater core isn't under pressure & has less chance of failure if it's a bit weak.

If that was true the suck side of your vacuum cleaner would be a compressor instead of a vacuum. Same principle. Putting a valve on the push side won't stop a leaking core from dripping I agree BUT it will take the pressure off & possibly save a core that is weak but not leaking yet.

In and of itself it won't cool the engine but running the heater with the fan on does aid cooling. It's an old trick to help cool off an overheating engine. I've done it myself and it does help.

It doesn't do anything for the occupants of the vehicle though

i took this off my 235 and installed it on my 292
http://s67.photobucket.com/albums/h298/1951otter/?action=view&current=DSC00313.jpg
as i remember when i had a leak that was only detectable when the core was mounted as that mounting caused a slight bend in the core,,,,,
i used the shut off valve to help diminish the flow & pressure off the core til i got round to soldering it .
any way you put it ... it did help.
or in a pinch simply bend the hose back on itself ... temp.

The heater valve regulates flow through the heater core.
The radiator cap regulates pressure of the cooling system.

Early Chevy cooling systems had zero pressure radiator caps.
The later 4-7 lbs. caps raised the coolant boiling point.

I once had both a radiator and heater core that only leaked when coolant was under pressure.
A zero pressure radiator cap reduced the leaks, until I could fix them.

Well, thankfully nothing is leaking yet!

When I installed the waterpump adapter I put on the original I think shut off valve since a heater will be installed soon,I noticed the motor warming up better with it flowing all the time but I will keep it shut off in the summer when the heater is installed. Jeff

Well guys, I have it on and I don't notice any difference heatwise with it on or off, there's too much floor missing to tell!

Looking into this.. how about having two shut off valves, one for each hose thus shutting off ALL pressure to the heater core in the summer? Any takers?

Well, it's a zero pressure system so I don't think it's going to make any difference at all in the health and longevity of your heater core.

My '39 Packard has a factory installed heater and factory installed shutoff valve on the inlet hose. If the designers thought a second shutoff valve would provide any benefit, I'm sure they would have installed one.

I’m locking this thread as the OP’s question has been answered.