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.

[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.

[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.

[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....

[beamn7]

My 85 Silverado doesn't have a heater control valve either. Just a blend door in the hvac unit....
Alot of motorhomes and stepvans still use the manual / cable operated heater control valve....
CJLINKSTER, your truck was not equipped with A/C from the factory. As mentioned, you have a Sanden compressor and the evaporator is not outside the firewall in the split case as a factory unit would be. May have been added at the dealer level. Was not uncommon to have that done....

[WarBeard]

I just went Out to look at my 89 V2500 Suburban and i don't see one either. I installed the same Autozone valve on that one too 5 or 6 years ago.

GM cars Always seem to have more bells and whistles than the trucks. I had two Cadillac's A 77 and a 81. When you opened the hood on one of them bad boys. It was 100 miles of vacuum hoses and valves LOL. What a nightmare!

[tucsonjwt]

I just joined the manual heater valve shutoff brigade. I got the same valve from O'Reilly for $11.44 with AZ tax - actually it was "free" because I used store credit cards I got from previous purchases of on sale oil, etc. The brand they had was Murray, but it looks the same. It does seem to make the A/C run cooler in the 100 degree ambient temperature with 454 heat blowing off the engine. I will keep an eye on the temp gauge to see if it creeps up on me.

[WarBeard]

Welcome to the club!...Now I'm driving this truck every day since the heater is not on during the summer!

[Tucson38]

How about using a ball valve from a plumbing supply place? Home Depot has one with with male barbed fittings (shark bite). These types of valves have heat ratings of either 200, 250, or 300 degrees.

[WarBeard]

Originally Posted by Tucson38

How about using a ball valve from a plumbing supply place? Home Depot has one with with male barbed fittings (shark bite). These types of valves have heat ratings of either 200, 250, or 300 degrees.

I would just be more money to get the same result. I think the valve alone is like 10 bucks. and then you need to get the 2 barbed fittings.

[TDS-MN]

How does this actually work? doesn't it create a 'dead-end' for the coolant flow? Granted that's probably low pressure (based on water pump flow) but still? Wouldn't a return or bypass be a better way to accomplish this end result? Just asking, as I would think that would not cost much more to loop the flow. . .

??

[WarBeard]

Originally Posted by TDS-MN

How does this actually work? doesn't it create a 'dead-end' for the coolant flow? Granted that's probably low pressure (based on water pump flow) but still? Wouldn't a return or bypass be a better way to accomplish this end result? Just asking, as I would think that would not cost much more to loop the flow. . .

??

It does create a dead end. But it doesn't matter, it wont hurt anything, been doing it for years. Making a loop IMO would dump hot water from the engine directly into the "Cool" side of the radiator and make your temps go up. Plus you will need to install a 5/8 to 3/4 fitting since the line going back into the radiator is bigger.

Plus! When you want your heater back all I have to do is open my valve. If you made a loop you have to reroute your hoses again and add coolant.

Like I said, once a month or so when your under the hood just open the valve and let the water flow for a few minutes.

.

[ghettoluxury]

As stated before Honda uses this from the factory for their heat control. It is a ball valve that is operated by a cable and only turns off the inlet flow. I have owned many Honda cars and never had a problem with heater cores.