installing shut off valve to heater core

[Mountain Man]

I have a problem with my heater in the cab still pumping in heat even when the cab control is turned off.

It has been suggested that an easy fix would be to install an inline on /off valve to the heater core.

Which line do I put the shut off valve on, the line that goes to the lower port on the heater core, or the upper line?

I don't use the truck in anything other than summer driving, but don't want to loop the line as we can get some cold spring mornings and cool summer evenings up here.

[hanssolo]

My catalog shows 4 diff. types of cutoff switches. I know it goes on the input side to the core, but which line it is I forget. The upper hose from the engine on a 350 I believe. Mine is in backwards and what happens is it does'nt circulate at idle.

[ThreeQuarter]

My '72 had a run-of-the-mill plumbing valve in the line connecting to the intake manifold. The previous owner was a plumber...

[2nova2]

OK i am having the same prob. so which hose is it for a non A/C truck. The way my hoses are run is a 3/4 hose from the water pump to the 3/4 fitting on the top of heater box and the 5/8 from the intake manifold to the bottom of heater box. So the question is, is the 3/4 on the top the incoming line and should the valve be on that one?

[Zkast]

Your hose coming from the intake is the supply(inlet)side. The hose going to the waterpump or radiator is the exhaust(outlet) side. Install the shutoff valve on the inlet side although I doubt it will make a huge difference which side you put it on.. When you install it on the inlet, it stops convection heating of the 180+ degree water....

[2nova2]

So what you are saying is the water flows out from the intake?

[Mountain Man]

Mine is the same set up as 2nova2, with the 3/4 hose from the water pump to the upper inlet on the heater core. The lower 5/8 hose is hooked up to the lower part of the heater core. Logic would say that the hose from the water pump to the top of the heater core would be the one to put the shut off valve on, because the pump would be sending heated coolant into the heater core, and then back out the smaller bottom hose and back into the intake port.

I need this clarified, as I want to splice into the right hose.


thanks.

[hwedding56]

Mine was the 5/8 '' hose That I installed it on. (looked nothing like the plumbers valve LOL) It does the same thing though. I would agree with Zcast it will stop the flow of hot water on the top or the bottom hose. look at your water pump when its running. That will tell you if its pushing the water or pulling it.
Herbie

[Dandeluxe]

mine was doing the same thing and i just took the hose off the top of the heatercore and ran it to the top of radiator no valve needed problem solved or is it top hose from water pump and put it to the radiator and no valve needed bypass the heater core is all your doing.

[2nova2]

Im with you Mountain Man I need clarification. I realize that you want to stop circulation, but i must be missing something, if you don't put the valve on the right hose won't hot water still flow to the heater core? therefore hot air into cab. Is it me?

[busterwivell]

I've done this with several vehicles before, and I always thought the top hose (at the heater core) was the correct one. To make the job quick and easy, I used small vice grips on both sides of the hose where I made the cut. Lost almost no coolant and made no mess that way. I worked for me. Of course, when it's 110 degrees in Tucson, it's hard to tell if the heater is off or on.

[Longhorn Man]

I would also think that it would be the hose off the water pump... best way to find out would be to disconnect it, let it drain into an aproved container(shop floor) and once it is done spilling, have an assistant (wife) fire it up. If it gushes from the hose, that is your supply, if from the core...return.
It really wouldn't matter too much if you got the wrong one blocked. If the water can not get out, then the hot water won't get in...kinda like a clogged radiater...it'll cool a little bit of water, but you'll still overheat since the cool water isn' going anywhere.

[racedvl]

The return goes into the water pump.

[billogna]

My original valve is in the 5/8" hose which goes to the intake. I can never remember which way the flow goes, either, I just ran mine like it shows in the assembly manual.

[Zkast]

Water flows from the intake to the core then to the pump. the hose going to the pump is on the inlet side of the pump meaning it will pull coolant from this hose and pump into each side of the block. Thats why the put the nipple at the front of the intake... thats the final place for coolant to flow before its sent back to the radiator, its also the hottest coolant in the entire system.

[CoryM]

The water pump nipple is suction, the intake is definatly,100% sure, the one you want to block. On my camaro i have it from the water pump and from the rad. both suction sides so its no good. It honestly doesnt matter what one you block off, so long as it stops flowing through the core but block the intake one off for best results.
CoryM

[Richard]

The intake manifold is the outlet and the hottest water which is why the heater is connected there and why the thermostat is placed there. That hose connects to the bottom inlet on the heater core. The upper outlet on the heater core goes to the pump. I can email a pic from the service manual if anyone would like to see. It really does not matter which hose the valve is put in because the water will not flow when shut off, but if you want shut it off at the supply put the valve in the hose from the manifold. Might try adjusting the air flap before you go to all the trouble though. The rubber seal may be shot also. Hope this helps.

Darn I type slow!

[blue72stepside]

This is why u should not block off the hoses:
If you examine the location and orientation of the heat exchanger in the radiator, you will see that it is located where the radiator's bypass water flow runs. Normally, the heater core is fed from an engine tap before the coolant thermostat, so that it sees warm water as soon as any significant heat has been produced by the engine warming up. The return water from the heater core is dumped back into the radiator in a place where it will flow across the heat exchanger before it re-enters the water pump and makes another circuit. This means that the heater core water, which warms up more quickly than the main radiator water, also serves to warm up the transmission fluid in the heat exchanger. This is important because warm transmission fluid is only a so-so lubricant, and cold transmission fluid is even worse. You want to get the fuid warmed up as soon as possible in order to lengthen the life and improve the durability of the transmission. The waste water from the heater core flowing over the heat exchanger does this. Fix the other problem.

[Longhorn Man]

In theory, that kinda sounds ok. but too bad they put block offs on the hoses from the factory in some trucks huh?

[PitterPats72]

Blue72stepside:
When you say fix the "other problem". What is the other problem. I have the same problem as all these guys and tell me what is the problem.

Is the problem that the flapper is not working correctly?

Tell me, in Indy when its's 85 you can tell there's heat coming in the cab.

Whoever had the picture from the manual can you email it to me? pitterpats72@bww.com .

thanks,
Pat

[72LNGHRN]

mine has the shut off from the factory which is working but still get heat in the cab thru the vents havent figured it out yet but I think one of the dampers is not fully closing this is on an a/c truck.

[blue72stepside]

yes it could be the flapper is not closing all the way or something stuck in it sticks, leaves, dead things. try moving it all the way to hot see if it gets hotter. We have one truck in are fleet that someone hooked up backwords some how, if u turn this thing to hot it gets cold. If you want to such the water flow to the heater core and still take care of the heat exchanger get a two way valve. in one position it will be normal in the other it will return to the radiator. the two way valve only applys to trucks with auto trans. I would also check to make sure the door is moveing
ie: the cable is hook up, door is moving. i an not such about a/c truck, don't they have a valve that shuts the water off when the a/c is on.

[tom hand]

It really doesn't matter. If you put a valve in either hose it will block flow of coolant to the heater core, no more heat.