Heater core shut off valve installed

[WarBeard]

Today I installed a shut off valve in my heater line. Even with all my heater controls turned to the off position I could still feel a lot of heat in the cab.

This job take's all of 5 minutes to complete if your truck is cooled off. I went to Autozone and asked for the valve. It fits 5/8 hose, and some hose clamps. Find the hose that runs from you engine to the firewall, cut it and install the valve tighten the clamps and your done. Make sure to replace any water/coolant that is lost due to cutting the hose.

Problem solved no more heat in the cab until I want it!!

[WarBeard]

Here is what it cost me.

[cjlinkster]

Does it matter if you install the valve into the upper or lower hose? Coolant enters the upper hose and returning from the bottom hose, right?

I have another silly question for you guys...

I have notice that some trucks have the plastic housing on the firewall for the AC components. I am guessing that some trucks (such as my 1984) have the components within the inside of the cab??? What was the reason for the change? Is this something that they changed on the later model trucks?

[primrrd]

looks like yours might have an aftermarket air conditioner?
Most squares without the big case on the right side of the firewall were Non-AC trucks (the heater core is in a case inside and under the dash, Stock ac has the split case and big accumulator dryer on the rt side of the firewall.
you have a sanden compressor (good unit) but your 84, if ac equipped from factory should also have a flat round (a4) compressor on the lt side of the engine.
What does the ac on the inside look like? is it an "under dash" unit?

[WarBeard]

I wish my truck had a Non A/C cab. As far as the hose question. The upper hose is 5/8 and the lower is 3/4. The valve I got from the parts store had 5/8 barbs on it. if you could find a valve with 3/4'' ends on it, that would work just fine.

Now if you Block off the lower hose It may be possible for the water in the heater core can still heat up????? I don't know really.

The upper hose is the most common way to do this. Block off the hot water before it even gets to the Heater core.

[76stepsidechevy]

I've been thinking about doing this as well. There isn't a need to run a bypass?

[v30crewcab]

just needs it on one side. just needs to stop the flow. did this to my truck a few days ago. honda and toyota use these for heater controls.

[WarBeard]

Originally Posted by 76stepsidechevy

I've been thinking about doing this as well. There isn't a need to run a bypass?

Nope no need to bypass. Every once in a while, while your under the hood open the valve to let the water flow for a little bit then close it back off. Thats just what I do.

[hatzie]

A1 and B1 chassis VW used a cable operated valve. I've thought about adding one to my CUCV.

[cjlinkster]

Originally Posted by primrrd

looks like yours might have an aftermarket air conditioner?
Most squares without the big case on the right side of the firewall were Non-AC trucks (the heater core is in a case inside and under the dash, Stock ac has the split case and big accumulator dryer on the rt side of the firewall.
you have a sanden compressor (good unit) but your 84, if ac equipped from factory should also have a flat round (a4) compressor on the lt side of the engine.
What does the ac on the inside look like? is it an "under dash" unit?

My truck is a camper special and appears to have factory air controls. There isn't an additional under the dash unit. I think that the accumulator dryer is mounted in front of the radiator.

I am going to install one of these shut off valves soon.

[willett]

I'm just throwing this out there but, It seems to me that you should always allow a bit of fluid flow through your heater core or it will prematurely rust out. Shoot me down if you don't agree but I wouldn't want the same fluid sitting in there for half the year.
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[Firebirdjones]

Originally Posted by motomech

Today I installed a shut off valve in my heater line. Even with all my heater controls turned to the off position I could still feel a lot of heat in the cab.

This job take's all of 5 minutes to complete if your truck is cooled off. I went to Autozone and asked for the valve. It fits 5/8 hose, and some hose clamps. Find the hose that runs from you engine to the firewall, cut it and install the valve tighten the clamps and your done. Make sure to replace any water/coolant that is lost due to cutting the hose.

Problem solved no more heat in the cab until I want it!!

I find it odd that you didn't have one from the factory since you have an air conditioned truck. Maybe these things were gone in the later 70's??

All of my AC equipped early 70's vehicles have a factory heater control valve. It runs off a vacuum line so it's open only when you turn the heat on. This is done to keep the hot coolant out of the heater box while running the AC unit (works more efficiently)
Different control valves mount different ways. Some of mine are mounted on the inner fender and the hose is simply cut, and a vacuum line runs to the heater controls.
My 71 nova is my favorite style, as it actually screws into the intake manifold and acts as a control valve and hose nipple all in one and makes for a much cleaner looking install with one piece of hose.

If your truck didn't have one originally (I guess GM eliminated this feature at some point??) Did you ever think of adding a factory one with a vacuum line? I wouldn't think it would be hard to do and you wouldn't have to keep popping the hood and turning a valve all the time.

[tucsonjwt]

Just my uneducated $.02, but I don't see why coolant staying in the heater core would be a problem unless you had bad coolant and contaminants precipitated out to the bottom of the heater core. I understand that the moving coolant has a flushing effect on the radiator cores, but since it ultimately moves out of the heater core during the winter it seems like that would not be a problem. You could alternately just open the valve once a month and let it flush. Sometimes my truck would sit for a month while I was driving my other vehicle and I saw no adverse effect on the heater core (however, the effect on old gas sitting in the carburetor caused very damaging varnish formation.
I still am curious about the bypass issue and if installing a shutoff valve in just the input line to the heater core would have any adverse effect.

[Firebirdjones]

Originally Posted by tucsonjwt

Just my uneducated $.02, but I don't see why coolant staying in the heater core would be a problem unless you had bad coolant and contaminants precipitated out to the bottom of the heater core. I understand that the moving coolant has a flushing effect on the radiator cores, but since it ultimately moves out of the heater core during the winter it seems like that would not be a problem. You could alternately just open the valve once a month and let it flush. Sometimes my truck would sit for a month while I was driving my other vehicle and I saw no adverse effect on the heater core (however, the effect on old gas sitting in the carburetor caused very damaging varnish formation.
I still am curious about the bypass issue and if installing a shutoff valve in just the input line to the heater core would have any adverse effect.

The original intention is what I hinted at above. It keeps the hot coolant out of the heater core so the AC works more efficiently. This was a factory valve on AC equipped cars and trucks for many years.

[WarBeard]

I have Never seen a valve from the Factory on any of my Squares. I install these valves on all of my trucks. I am under the hood a lot checking things like oil and stuff and I just open the valve for a few minutes and let the water flow. I have only had one heater core fail on me but I chalk that up to being a nearly 40 year old truck.

Secondly LOL, I hate vacuum lines and one less line makes me happy

I would like to see a picture or link to a factory installed valve as I have never seen one.

[Firebirdjones]

Originally Posted by motomech

I have Never seen a valve from the Factory on any of my Squares. I install these valves on all of my trucks. I am under the hood a lot checking things like oil and stuff and I just open the valve for a few minutes and let the water flow. I have only had one heater core fail on me but I chalk that up to being a nearly 40 year old truck.

Secondly LOL, I hate vacuum lines and one less line makes me happy

I would like to see a picture or link to a factory installed valve as I have never seen one.

They were installed on thousands of cars/trucks but I'm not sure when GM stopped doing it.

Hang on and I'll find a pic of one of mine....

[Firebirdjones]

Here's one of my 72 blazer with a factory heater control valve. Hard to see in the pic so I circled it. Vacuum line T's into the main line for the heater control vacuum door. So it opens the valve when the heater is turned on. Very simple setup.

[Firebirdjones]

Well shucks, I suck at computers and the circle didn't show up.

Take a close look at the inner fender, you'll see the small circular gold cad plated vacuum pod that the heater hose runs to. I was lucky on this truck that it had this version of the valve, because the LS engine doesn't have an intake port for it like the old cars did. The other version of this valve screws right into the intake manifold where you would normally see a heater hose nipple.

One reason they are seldom seen anymore is that when they started leaking, rather than replace them people would just discard them. As far as I know they were always on the AC equipped cars/trucks. Non AC vehicles didn't get it.

[WarBeard]

That's pretty cool Ive never seen one. I wonder if they stopped using them in the Squarebodys?

VERY clean LS Swap!

[Firebirdjones]

Squarebodies endured a rather long production (70's-80's-90's). I have a 79 454 1 ton with factory air. I can't remember if it has one or not, I'll have to go look but I'm betting it does. I should know I've owned the darn thing 15 years and just tossed and 502 in it. Memory sucks when you get old,,,,lol.

I know GM was still using them on cars in the 80's, not sure about trucks. I'm pretty sure once things went electronic there was no need for these control valves anymore.

I'd have to investigate it a little further as I never gave it all that much thought until now, and as I mentioned, most of these were removed and never replaced (people didn't want to deal with them I guess not knowing it would affect the AC efficiency) so unless you can look at an original unmollested vehicle it's hard to say whether it would have had one.

[Firebirdjones]

Hey I just noticed the circle is there now,,,wasn't before though.

I did it right

[clinebarger]

My 85 C20 factory air burb never had a heater control valve (Been in the family since new). Though they do benefit from installing one.

[Firebirdjones]

Originally Posted by clinebarger

My 85 C20 factory air burb never had a heater control valve (Been in the family since new). Though they do benefit from installing one.

Now here is a good example. I don't know where the cars may have differed from the trucks, and this is starting to get into the electronic age too.

[clinebarger]

Originally Posted by Firebirdjones

Now here is a good example. I don't know where the cars may have differed from the trucks, and this is starting to get into the electronic age too.

The G-bodies used them till '87, B-body till '90. Im pretty sure Square's dont. I think it has alot to do with the evaorator/heater core case design.

[Firebirdjones]

Originally Posted by clinebarger

The G-bodies used them till '87, B-body till '90. Im pretty sure Square's dont. I think it has alot to do with the evaorator/heater core case design.

Ah there ya go, probably right in that the design of the case had something to do with it. I knew the G-bodies still used them in the 80's, my fathers 81 and then 86 both had them.