Heater core shut off valve - The 1947 - Present Chevrolet & GMC Truck Message Board Network

External · 04-03-2021, 09:45 PM

Hey everyone!
I read somewhere on here that someone had put a valve on their heater core inlet hose. So that the hot water would not circulate in the heater core.
I'm interested in this fix as summer approaches.
My heater shut off is worn out and allows hot air into the cab all the time.

My question: Will adding a valve in my system cause any problems?
Any advice is much appreciated.

Andy4639 · 04-03-2021, 09:51 PM

I have run them for years with no problems. If you have AC in the truck it's worth every penny. When I installed the one in my 71 C 10 I got 5* more out of my AC.

Pictures are of the one in my Ramp truck.

pwdcougar · 04-03-2021, 09:59 PM

I've had one on my 69 Cougar for 20 years with no problems. I used a solder connection type brass ball valve and soldered on a couple inches of copper pipe and put two clamps on each side.

**Grumpy old man** · 04-03-2021, 10:08 PM

https://www.autozone.com/cooling-hea...E&gclsrc=aw.ds

Rich72C10 · 04-04-2021, 07:18 AM

Quote:

Originally Posted by Grumpy old man

https://www.autozone.com/cooling-hea...E&gclsrc=aw.ds

Grumpy, I assume that is more like a OEM cut off?

**Grumpy old man** · 04-04-2021, 08:05 AM

Quote:

Originally Posted by Rich72C10

Grumpy, I assume that is more like a OEM cut off?

They've been around forever , it's inexpensive at around $10.00 at your local parts house and installed in minutes .

And they look good , Not like you stole the plumbing off your grandmothers water heater !

Rich72C10 · 04-03-2021, 10:44 PM

So which line to you put it on, from the block or the Radiator?

I ask since the A/C shop put one on for me but it shuts off from the Radiator. Seems it would work better from the block side, in front of the vacuum control shut off valve.

**Stocker** · 04-04-2021, 12:18 AM

Put the valve on the hose from the engine -- that is the heat source. The hose to the radiator is for water exiting the heater core.

**Richard** · 04-04-2021, 02:03 AM

The vacuum shut off valve should be standard on an A/C truck. Basically does not matter what hose it is installed in, will stop the flow, in the heat side does make make sense.

Rich72C10 · 04-04-2021, 07:08 AM

Quote:

Originally Posted by Stocker

Put the valve on the hose from the engine -- that is the heat source. The hose to the radiator is for water exiting the heater core.

That is what I was thinking too, it would make more sense for the shut off to be on source side. I'd just figured the A/C guy knew something different.

Quote:

Originally Posted by Richard

The vacuum shut off valve should be standard on an A/C truck. Basically does not matter what hose it is installed in, will stop the flow, in the heat side does make make sense.

Yes, understand it is standard and I do have a new one but my understanding they kind of suck - so that is why I asked for a manual shut off value when the A/C was being fixed & upgraded.

Now I need to decide when/if to move it over to the inlet/engine source side. It's one of those things I look at and scratch my head about .... "is that right?". At some point I suppose I'll just do it because it will get on my nerves LOL

Edit: NM my hoses are actually correct.

Quote:

Originally Posted by franken

Ok, laugh at me...
This is to reduce hotness in the cab in the summer? I've seen them in a few trucks and wondered...

That pretty much it, to 100% stop hot water flow in the cab. If any hot water flow gets to the coil it affects the efficiency of the A/C (and I'd image any cool air you are trying to get if you haven't A/C).

franken · 04-04-2021, 03:57 AM

Ok, laugh at me...
This is to reduce hotness in the cab in the summer? I've seen them in a few trucks and wondered...

Rich72C10 · 04-04-2021, 08:30 AM

ya, I am pretty sure you (or someone else) commented on one of my post where the A/C guy installed a setup much like Andy's. Which is exactly the same cut off valve I installed on my water heater LOL!

**Grumpy old man** · 04-04-2021, 08:46 AM

Hey , it's your truck use whatever makes you happy .

Rich72C10 · 04-04-2021, 09:36 AM

Well, I didn’t do it and I can say I was all that happy. But now I am, since I just changed it.

External · 04-04-2021, 10:07 AM

Really appreciate the posts, stories, and replies.
Always learning from you all here.
Happy Easter!
Now I'm going to go shut off the hot water flow!

Rich72C10 · 04-04-2021, 10:36 AM

Your post helped me as much as you External - got me motivated to sort mine out! I even did a bit more rerouting and the inlet line isn't touching any of the A/C lines now. I also cut down the water reserve line as it was like a mile long - so it's nice and tidy all around on that side with water lines.

Have fun - the more you visit these forums the more you learn you need to do to your truck LOL!

BigBird05 · 04-04-2021, 12:38 PM

If your looking for original GM look, early 60's AC cars ( I would start with Cadillac or Buick or Olds) had a vacuum shut off valve.

**pjmoreland** · 04-04-2021, 01:41 PM

I installed Vortec heads, which are lacking a coolant hole that older heads have for recirculation before the thermostat opens. I am relying on my heater core for recirculation, so installing a manual shutoff valve to the heater core would be a bad move in my case. I would have to install a thermostat bypass hose between the water pump and front of the intake manifold. I really don't like how those bypass hoses look. I will have to do that eventually though if I add AC to my truck.

Andy4639 · 04-04-2021, 08:23 PM

Well I was going to post something but I want since it's Easter Sunday.
Both my trucks perform well and I'll just leave it at that.
There is always someone.
Good luck with it. I hope you figure it out.

**pjmoreland** · 04-04-2021, 09:49 PM

I hope I didn't say anything that upset you. I was talking about the little hose people have to add to the front of the intake manifold when running Vortec heads on trucks with AC.

SCOTI · 04-06-2021, 10:02 AM

Apparently some later model vehicles require flow on the path to the heater core or suffer cavitation issues. I recently learned this & was not aware. These set-ups actually have a bypass that stops flow to the heater core (similar to these cut-off valves) yet allows for the loop to still circulate.

I learned about them on various LS swaps I've seen on the web.

pwdcougar · 04-06-2021, 12:51 PM

Quote:

Originally Posted by SCOTI

Apparently some later model vehicles require flow on the path to the heater core or suffer cavitation issues. I recently learned this & was not aware. These set-ups actually have a bypass that stops flow to the heater core (similar to these cut-off valves) yet allows for the loop to still circulate.

I learned about them on various LS swaps I've seen on the web.

Yes I found this out when I bypassed the heater core on a 97 Buick Century. The heater core is an integral part of the cooling system. I installed a bypass valve that was for a Ford Ranger

SCOTI · 04-06-2021, 01:52 PM

Quote:

Originally Posted by pwdcougar

Yes I found this out when I bypassed the heater core on a 97 Buick Century. The heater core is an integral part of the cooling system. I installed a bypass valve that was for a Ford Ranger

I never gave these much thought.

I had a primitive bypass set-up (as in using what I had available for free vs spending money for something that may not impact my issue) for my 74swb @ one point. I was struggling w/heat soak on the a/c & wanted to see if blocking the hot-water flow to the heater core helped. I built a similar, simple hand valve set-up as it's what I had available for testing.

I knew there were early OE versions of a vacuum/temp actuated bypass valve (from GM) available but wasn't going to spend the money for one just to find out it didn't make a difference for my needs.

Killer Bee · 04-06-2021, 02:06 PM

wait... what?? there's a valve that does this?

71longbed-brew · 04-06-2021, 10:27 AM

Can this be done on a non-ac truck ?

04-03-2021, 09:45 PM	#1
External Registered User Join Date: Jun 2018 Location: Louisiana Posts: 185	Heater core shut off valve Hey everyone! I read somewhere on here that someone had put a valve on their heater core inlet hose. So that the hot water would not circulate in the heater core. I'm interested in this fix as summer approaches. My heater shut off is worn out and allows hot air into the cab all the time. My question: Will adding a valve in my system cause any problems? Any advice is much appreciated. __________________ '72 Chevy Custom Deluxe Highlander. Med Olive/White 350/200 ps,pb and Air Conditioning!

04-03-2021, 09:51 PM	#2
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: Heater core shut off valve I have run them for years with no problems. If you have AC in the truck it's worth every penny. When I installed the one in my 71 C 10 I got 5* more out of my AC. Pictures are of the one in my Ramp truck. Attached Images __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

04-03-2021, 09:59 PM	#3
pwdcougar Registered User Join Date: Oct 2013 Location: New Jersey Posts: 1,307	Re: Heater core shut off valve I've had one on my 69 Cougar for 20 years with no problems. I used a solder connection type brass ball valve and soldered on a couple inches of copper pipe and put two clamps on each side. __________________ "You know that little thing in your head that keeps you from saying things you shouldn't? Yeah well, I don't have one of those" 1969 Mercury Cougar Standard 4 speed 1969 Mercury Cougar XR7 convertible 1970 4WD Chevrolet Suburban 1997 4WD Chevrolet Silverado Extended Cab Short Bed (purchased new January 1997)

04-03-2021, 10:08 PM	#4
Grumpy old man Senior Member Join Date: Dec 2013 Location: Gods country East,Tn Posts: 8,545	Re: Heater core shut off valve https://www.autozone.com/cooling-hea...E&gclsrc=aw.ds Attached Images __________________ 1967 Factory short bed - Old school '71 - 350 / 4bolt / 487 heads / Edelbrock C3BX Muncie M-22 4 speed / Hurst Comp plus Factory 12 bolt posi 3.73 / 255-70-15 Smoothed firewall / Factory cowl induction Power disc brakes / power steering / 3.5-5" drop

04-03-2021, 10:44 PM	#7
Rich72C10 Mr. Cheyenne Join Date: Jun 2020 Location: Kyle, Texas Posts: 1,687	Re: Heater core shut off valve So which line to you put it on, from the block or the Radiator? I ask since the A/C shop put one on for me but it shuts off from the Radiator. Seems it would work better from the block side, in front of the vacuum control shut off valve. __________________ Richard *'72 Chevy C10 Cheyenne Super WHT/MED BRONZE/WHT SBC 350 \| TH350 \| LWB \| AC \| Buddy Seats Upgrades:** Tilt \| Front Sway Bar \| Radio \| Sliding Window \| Bed Spare w/Lock Bed Rails \| Full LEDs \| Courtesy Lights \| Tachometer \| Glovebox Lock & Light \| Head Light Relays \| *Upgraded Fully Super Trim

04-04-2021, 12:18 AM	#8
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,691	Re: Heater core shut off valve Put the valve on the hose from the engine -- that is the heat source. The hose to the radiator is for water exiting the heater core. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

04-04-2021, 02:03 AM	#9
Richard Senior Member Join Date: Dec 1999 Location: Southern California Posts: 2,854	Re: Heater core shut off valve The vacuum shut off valve should be standard on an A/C truck. Basically does not matter what hose it is installed in, will stop the flow, in the heat side does make make sense. __________________ Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746

04-04-2021, 03:57 AM	#11
franken Registered User Join Date: Jun 2013 Location: Somewhere Posts: 3,101	Re: Heater core shut off valve Ok, laugh at me... This is to reduce hotness in the cab in the summer? I've seen them in a few trucks and wondered...

04-04-2021, 08:30 AM	#12
Rich72C10 Mr. Cheyenne Join Date: Jun 2020 Location: Kyle, Texas Posts: 1,687	Re: Heater core shut off valve ya, I am pretty sure you (or someone else) commented on one of my post where the A/C guy installed a setup much like Andy's. Which is exactly the same cut off valve I installed on my water heater LOL! __________________ Richard *'72 Chevy C10 Cheyenne Super WHT/MED BRONZE/WHT SBC 350 \| TH350 \| LWB \| AC \| Buddy Seats Upgrades:** Tilt \| Front Sway Bar \| Radio \| Sliding Window \| Bed Spare w/Lock Bed Rails \| Full LEDs \| Courtesy Lights \| Tachometer \| Glovebox Lock & Light \| Head Light Relays \| *Upgraded Fully Super Trim

04-04-2021, 08:46 AM	#13
Grumpy old man Senior Member Join Date: Dec 2013 Location: Gods country East,Tn Posts: 8,545	Re: Heater core shut off valve Hey , it's your truck use whatever makes you happy . __________________ 1967 Factory short bed - Old school '71 - 350 / 4bolt / 487 heads / Edelbrock C3BX Muncie M-22 4 speed / Hurst Comp plus Factory 12 bolt posi 3.73 / 255-70-15 Smoothed firewall / Factory cowl induction Power disc brakes / power steering / 3.5-5" drop

04-04-2021, 09:36 AM	#14
Rich72C10 Mr. Cheyenne Join Date: Jun 2020 Location: Kyle, Texas Posts: 1,687	Re: Heater core shut off valve Well, I didn’t do it and I can say I was all that happy. But now I am, since I just changed it. Attached Images __________________ Richard *'72 Chevy C10 Cheyenne Super WHT/MED BRONZE/WHT SBC 350 \| TH350 \| LWB \| AC \| Buddy Seats Upgrades:** Tilt \| Front Sway Bar \| Radio \| Sliding Window \| Bed Spare w/Lock Bed Rails \| Full LEDs \| Courtesy Lights \| Tachometer \| Glovebox Lock & Light \| Head Light Relays \| Upgraded Fully Super Trim Last edited by Rich72C10; 04-04-2021 at 10:28 AM.*

04-04-2021, 10:07 AM	#15
External Registered User Join Date: Jun 2018 Location: Louisiana Posts: 185	Re: Heater core shut off valve Really appreciate the posts, stories, and replies. Always learning from you all here. Happy Easter! Now I'm going to go shut off the hot water flow! __________________ '72 Chevy Custom Deluxe Highlander. Med Olive/White 350/200 ps,pb and Air Conditioning!

04-04-2021, 10:36 AM	#16
Rich72C10 Mr. Cheyenne Join Date: Jun 2020 Location: Kyle, Texas Posts: 1,687	Re: Heater core shut off valve Your post helped me as much as you External - got me motivated to sort mine out! I even did a bit more rerouting and the inlet line isn't touching any of the A/C lines now. I also cut down the water reserve line as it was like a mile long - so it's nice and tidy all around on that side with water lines. Have fun - the more you visit these forums the more you learn you need to do to your truck LOL! __________________ Richard *'72 Chevy C10 Cheyenne Super WHT/MED BRONZE/WHT SBC 350 \| TH350 \| LWB \| AC \| Buddy Seats Upgrades:** Tilt \| Front Sway Bar \| Radio \| Sliding Window \| Bed Spare w/Lock Bed Rails \| Full LEDs \| Courtesy Lights \| Tachometer \| Glovebox Lock & Light \| Head Light Relays \| *Upgraded Fully Super Trim

04-04-2021, 12:38 PM	#17
BigBird05 Registered User Join Date: Aug 2019 Location: Cheraw Posts: 1,300	Re: Heater core shut off valve If your looking for original GM look, early 60's AC cars ( I would start with Cadillac or Buick or Olds) had a vacuum shut off valve.

04-04-2021, 01:41 PM	#18
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,770	Re: Heater core shut off valve I installed Vortec heads, which are lacking a coolant hole that older heads have for recirculation before the thermostat opens. I am relying on my heater core for recirculation, so installing a manual shutoff valve to the heater core would be a bad move in my case. I would have to install a thermostat bypass hose between the water pump and front of the intake manifold. I really don't like how those bypass hoses look. I will have to do that eventually though if I add AC to my truck.



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04-04-2021, 08:23 PM	#19
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: Heater core shut off valve Well I was going to post something but I want since it's Easter Sunday. Both my trucks perform well and I'll just leave it at that. There is always someone. Good luck with it. I hope you figure it out. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

04-04-2021, 09:49 PM	#20
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,770	Re: Heater core shut off valve I hope I didn't say anything that upset you. I was talking about the little hose people have to add to the front of the intake manifold when running Vortec heads on trucks with AC.

04-06-2021, 10:02 AM	#21
SCOTI Registered User Join Date: Apr 2001 Location: DALLAS,TX Posts: 22,031	Re: Heater core shut off valve Apparently some later model vehicles require flow on the path to the heater core or suffer cavitation issues. I recently learned this & was not aware. These set-ups actually have a bypass that stops flow to the heater core (similar to these cut-off valves) yet allows for the loop to still circulate. I learned about them on various LS swaps I've seen on the web. __________________ 67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... *Cubic inches is like Indiana Jones with a cheap pistol.*

04-06-2021, 02:06 PM	#24
Killer Bee Registered User Join Date: Jan 2016 Location: Barber City, CA Posts: 4,795	Re: Heater core shut off valve wait... what?? there's a valve that does this? __________________ *I started out with nothing - and I still have most of it*

04-06-2021, 10:27 AM	#25
71longbed-brew Registered User Join Date: Sep 2008 Location: Salem Oregon Posts: 64	Re: Heater core shut off valve Can this be done on a non-ac truck ? __________________ 350/th350 DNA (Chinesium) Heads Performer Intake 1905 AVS2 Edelbrock 3.42 Eaton Posi

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