Heater (rear) isolation valves.

[Pinger]

Early on when I joined this forum I saw someone had put isolation valves/taps/stop-***** in the rear heater lines of a Suburban and I'm thinking of doing the same - so that I don't get stranded with no coolant should anything go awry with my heating system. So, I have some questions.

When this is done, is to isolate only the rear heater matrix or the front one also - ie, before the tees?

The hard lines running to the rear and back appear vulnerable - do they corrode from the outside in or inside out?

Is the front heater troublesome enough to warrant isolating it?
Without any heating (if anyone has experienced this) is the truck still usable in winter - ie, is there enough heat radiated from the engine bay into the cabin through the firewall to make driving bearable? (Winter = temps around freezing).


What do you use as a valve? Is it from the automotive world or domestic plumbing?
Can anyone confirm the ID of these hoses is 3/4'' (19mm)?

Anything else worth knowing?

Strikes me that this is a useful mod for any longroofer to consider so all and any info could be appreciated by more than just me. My thoughts are to do this in conjunction with addressing a coolant leak from around the inlet manifold area. This could be a good mod for any longroofer to do when they are replacing an inlet manifold gasket and have the coolant partly drained.
TIA.

 

[SAATR]

I have this exact valve installed on my heater circuit in my Suburban. I did so due to repeated heater core and plastic tee failures on my front circuit. Heat is almost non-existent without coolant flow, as the firewall and floor insulation blocks a great deal of radiant heat. A secondary purpose was to be able to shut the heater circuit down completely during the summer in order to give my AC system the best possible conditions for maximum performance.

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[Pinger]

I have this exact valve installed on my heater circuit in my Suburban. I did so due to repeated heater core and plastic tee failures on my front circuit. Heat is almost non-existent without coolant flow, as the firewall and floor insulation blocks a great deal of radiant heat. A secondary purpose was to be able to shut the heater circuit down completely during the summer in order to give my AC system the best possible conditions for maximum performance.

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Thanks.
Was it you posting about this then that I read about it? And are they valves for domestic plumbing? For some reason a plastic bodied valve is in my head.

And two are needed - another for the return line also?

 

[Erik the Awful]

No, one is enough to stop flow through your heater hoses. If you look in the junkyard you might find some vehicles that came from the factory with cable operated valves. Any time you weren't using the heater it shut the flow off from the heater core. Might even be some electrically operated. I've seen trucks with garden spigots plumbed in for the same reason. Personally, I'd rather not add another point of failure. I can always vise-grip a hose closed if need be.

 

[JavaMan]

Personally, I'd rather not add another point of failure. I can always vise-grip a hose closed if need be.

While I understand not wanting points of failure, pinching a hose is itself a point of failure, as the pinch point weakens the rubber hose.

I've been towed twice now due to those plastic T connectors breaking. They don't like the summer heat. I've been looking for metal T's to replace them, but haven't been able to find the right diameter. Think when I find them, I will also add this valve, and reduce my worry. Sounds like a good help for the AC as well, mine struggles with 110+ desert heat.

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[454cid]

I've never seen the rear heat system, but I'm pretty sure two valves would be needed to isolate it. You have a supply line, and a return line. Blocking the supply will prevent a steady supply of hot coolant from getting to the core, but it's not going to prevent coolant from exiting the system through a leak.

 

[east302]

Think when I find them, I will also add this valve, and reduce my worry. Sounds like a good help for the AC as well, mine struggles with 110+ desert heat.

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You probably already have a (plastic) isolation valve that closes when the ‘max’ detent is selected on the dash temperature dial. It closes coolant to the heater core and is meant to improve a/c performance. When closed, the coolant just circulates through the valve to the adjacent return line - it’s not a dead leg, in other words.

Here it is on a Tahoe without rear air. It’s vacuum actuated via a solenoid on the firewall. Not sure how it is configured on a Suburban.

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[thegawd]

Well I had or I should say my wife had a tire detread itself and RIP off all of the rear lines all together. I wasnt with her and got a frantic call..... the truck is on fire and I'm running away.... turns out it was coolant pouring on the exhaust. And she had no idea there was a fire extinguisher under the seat. ****

Eventually I get to her and had to bypass it on the truck on the side of the road. I keep basic tools and small parts in the truck. So I cut up a rubber section somewhere down towards the rear heater that's shaped like a U. Where these lines run through the frame is where I placed the U with a couple gear clamps I had in the truck. Now I do really want to bypass the entire system up in the cab and get rid of the plastic crap but all of it checks out and I do inspect it regularly. Only buy stainless gear clamps.

So I have had no rear heat for 2 years now, one real winter and the last wasnt cold at all. My front heater has been completely rebuilt and it pushes warm air to the back just fine. I always let the truck warm up in the winter before I take off though. ever looked up the prices of those lines complete from the front to the rear.... fix it anyway you can or bypass it all together.

Al

 

[SAATR]

Thanks.
Was it you posting about this then that I read about it? And are they valves for domestic plumbing? For some reason a plastic bodied valve is in my head.

And two are needed - another for the return line also?

Probably was me. I posted about it several years ago when I installed the valves. They are not fresh water supply or any sort of household plumbing valve, and I would not recommend using such due to questionable compatibility with the coolant chemistry, ambient and coolant temperatures, and the vibration associated with a mobile installation. The valve pictures has been problem free for several years, and I have seen them used in heavy equipment installations for much longer than that with no issues.

Only one valve is required to stop coolant flow through the circuit, but two are necessary if you want to be able to shut the heater circuit off completely in the event of a failure.

 

[Pinger]

I've never seen the rear heat system, but I'm pretty sure two valves would be needed to isolate it. You have a supply line, and a return line. Blocking the supply will prevent a steady supply of hot coolant from getting to the core, but it's not going to prevent coolant from exiting the system through a leak.

My thinking also.
What I want is to be able to completely isolate the circuits at the merest suggestion of a leak and be able to top up (with tap water if necessary) to get me home.
Mine is complicated as I'll need three valves. If I have to isolate I'll have to have a bridging valve to open to maintain coolant flow through the LPG (propane) reducer. It is first in line ahead of the plastic tees.

Given the plastic tees are a weak point, isolating upstream from them seems to be the way to go.