bypass heater core? coolant flow diagram?

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merrill77
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bypass heater core? coolant flow diagram?

Post by merrill77 »

I am considering bypassing the heater core to increase A/C efficiency in the summer. I'll need heat in the winter, so I'd like to simply turn a valve or two, rather than move hoses (and spill coolant).

So I was looking at the cooling system layout. I see a line running from the back of the block to the heater core, then to the pump. From there, it goes back into the engine, right? So hot coolant is coming right back into the engine? That seems non-optimal...well, in the summer. Seems like it should go to the radiator for cooling before returning to the engine.

Obviously this is different from the winter...where (a) if the heater is on, the coolant will be much cooled coming back to the engine and (b) total cooling system efficiency is not as critical due to ambient air temps.

If I just put a valve on the line from the back of the manifold to the heater core, then no coolant is leaving the back of the block. Assuming the engine was not designed for that, then perhaps a bad idea? In which case, I need a by-pass, not a cut-off, so the loop is still completed. Correct?

But would it not be better to run that directly to the radiator (in the summer)? Perhaps that would lengthen the engine warm-up duration.

I'm not confident in my understanding of the full path of coolant flow. I can see the hoses, but I don't know how it flows in the pump and heads (and manifold?). Has anyone diagrammed that?

TIA!
Chris
77 Wagoneer and 97 TJ.
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rainman
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Re: bypass heater core? coolant flow diagram?

Post by rainman »

I used a valve (Motorcraft YG350 equivalent) and removed the vacuum part and attached the lever to a universal choke cable ran to the dash.

Since I don’t have an AMC engine any more I can’t help you on which hose is which.
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SJTD
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Re: bypass heater core? coolant flow diagram?

Post by SJTD »

Since the heater is under the hood and completely separate from the AC system I'm skeptical that you'd gain anything unless your heater doors leak.

I also wonder if the engine needs that circulation for the cooling system to operate properly.
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1979bettywhite
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Re: bypass heater core? coolant flow diagram?

Post by 1979bettywhite »

I have also thought of bypassing my heater core as well, but that would mainly be to remove the core and box to get the core tested for leaks as well as repair a small hole in my box. On mine, I think that would be as easy as just connecting the in and out lines with a connector to keep the flow of fluid moving.

440sixpack
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Re: bypass heater core? coolant flow diagram?

Post by 440sixpack »

Put a valve on the intake . any valve will do but you can still get the one AMC used on cars at most parts stores. it's set up for a cable from the heater control but you can simply move it manually as well.

There is no need to pass coolant through the heater. if AMC V8 cars didn't need it Jeeps don't.
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Curly
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Re: bypass heater core? coolant flow diagram?

Post by Curly »

I'm with SJTD, heater is separate from A/C unit, totally different housing. I don't see how bypassing the heater will help A/C efficiency.
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merrill77
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Re: bypass heater core? coolant flow diagram?

Post by merrill77 »

Y'all are absolutely right! Dunno what I was thinking...especially since I dropped the A/C a few weeks ago so I could replace the heater core! I must have been picturing my TJ's heater box in my mind...replaced that a few months before tackling the Wagoneer.

But I do still wonder why the return from the heater goes back to the pump instead of the radiator? Is it to allow circulation to heater when thermostat is closed?
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tgreese
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Re: bypass heater core? coolant flow diagram?

Post by tgreese »

Coolant comes out of the top of the intake manifold, flows through the heater core, and back to the water pump. This is so that coolant circulates through the heater core regardless of whether the thermostat is open or not. Coolant circulates via the bypass hose when the thermostat is closed.

NB this is described in the TSM.
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