So Ive had my heater disconnect for a couple of years and I just changed the heater core (pain in the ***, note: buy one from the ac/delco store the aluminum advance auto parts one did not fit).

Anyway there are 2 sizes on the heater core 1/2" and 5/8". Which one do I run to the manifold and which one runs to the water pump? And which one do I put the hot water shutoff valve in??

I thought I had to run it to the radiator but everyone was telling me I should block that off and run it to the water pump.

 

There's a flow diagram in the attached link, post #16(site won't let me upload the diagram again). I know your engine isn't like the one in the pic, but this will still show you the general routing of the hoses.

https://www.thirdgen.org/forums/tpi/...ss-heator.html

The manifold feeds the heater core, so the diverter valve fits between the manifold and the heater core. And facing the firewall, the heater core inlet nipple is the one on the left, and the heater core outlet nipple is the one on the right. So...

A hose goes from the manifold to the inlet nipple on the diverter valve(and there should be a vacuum line laying around to connect to the top of the valve). Then of the pair of outlet nipples on the valve: the top outlet nipple returns to the radiator; the bottom outlet nipple goes to the heater core inlet(nipple on the left).

The hose from the heater core outlet(nipple on the right) returns to the radiator, but it joins-up with the hose from the diverter valve's upper outlet on its way to the radiator. So these are the hoses that you could choose to return to the water pump instead of the radiator. But because they join-up, it might be simpler to just let them go to the radiator, rather than trying to re-route them to the water pump. It would probably look better too, if that's important to you.

 

Does your water pump have provision for the heater-hose connection, a pipe plug?

JamesC

 

Well first off I realized the parts guy gave me the wrong size hoses, the right sizes are 5/8" and 3/4". So I went back to the store for the tenth time today.

I am not using a diverter valve since my engine is a carb swap, I bought a regular vacuum operated shutoff valve with 1 inlet and 1 outlet. I know I don't need it but the a/c has been removed and I don't want it to be any hotter than it needs to be inside. And since I have the vacuum line for it on my car already I bought it.


I have the the 3/4" line going from the heater core to the radiator.

The 5/8" line goes from the heater core to the shutoff valve and then to the manifold.


My waterpump does have a pipe plug on it. So far everything is working.

I guess it is supposed to go to the radiator and not the waterpump, we checked my friends '85 monte carlo and his was going to the water pump and he didn't even have a fitting on the radiator. I am wondering why most every small block chevy has it run this way, maybe its because of the serpentine reverse flow water pump?


The way I see it the coolant comes out of the manifold to the shutoff valve to the heater core out and to the radiator. When you move the blend door to cool (or a/c) vacuum is applied to the valve and shuts off coolant flow to the heater core.

 

I m taking out my stock oil cooler lines. how would I route the hoses so that i can still have heat? i am using an HSR

 

nvm dumb question

 

im putting a new motor in my 89 camaro so im going to change the heater hose routing becuase im putting an edelbrock FI system on it so the manifold is different. i dont think it has a spot for my heater hose.
can i run from the water pump (where mine has a plug now) to the heater core then back to the radiator? i wasnt sure because im using the stock serpentene set up and the water pump runs in reverse from what i have read.

 

it should have at least one spot on the manifold for it. The waterpump/rad is for return.

 

i just looked to make sure and this time i noticed a threaded hole on the right side (passenger side) of where the thermostat is. on the other side of the thermostat housing is the temp sensor for the new computer. i think that should work to go to the heater core then back to the rad.

 

1986 camaro, 350, carb. no air. Currently have a hose from intake to right side of core and a hose from the left side of core to water pump. I would think that the water pump feeds the core, is that correct. so which side should it be hooked up to. I would like to put a manual shut off for summer. Just realized that it takes 2 diff. size hoses. NO WONDER THE RIGHT HOSE ON THE CORE LEAKS ONCE IN A WHILE. Thanks

 

By a vacuum operated shutoff and hook it to your heater controls. The water pump is for return.

Run the 3/4" hose from the heater core to the water pump, and the 5/8" hose goes from the heater core to the shutoff valve and then to the manifold.

 

im just going to run the return to the radiator like it was stock. and the side that went to the back of the intake on my old 305... ill run that to the front of the intake on that new intake manifold i have. that should work?

 

Here's some info, that I hope will be generally useful.

The water routing on FI third-gens serves multiple purposes.
On TBI's there's an outlet, at the rear of the intake manifold,
that goes into the control valve, which routes it through the
heater core, then back to the radiator, or directly to the radiator.
This circulation pattern improves coolant flow through the back
of the engine/cylinder heads, one of GM's better ideas.

On TPI's the outlet is near the front, by the throttle body, so
I'm not sure of the internal manifold flow. But from the manifold,
routing through the control valve is identical.

In both instances, intake manifold heating occurs, and changing this
routing can have unintended consequences for the ECM control functions.

Carburated manifold heating is usually done with exhaust gas, so routing
of heater hose flow is less critical. Get it from any outlet, into the
heater, and back into flow towards the radiator. A control valve is optional,
and a simple 2 connection "on/off" is sufficient, as opposed to the 3
connection routing function & t-pipe for FI configs.

Clear as muddy water???

 

well this new EFI kit i got is more like the TPI with that opening for the heater on the front of the manifold. i was not planing on using an on/off valve in the heater lines.
then back to the radiator from the heater core like i said before.

 

I eliminated ac and shaped my 305 for a 350 in my 92 rs there are only 2 hoses a larger hose and looks like a 5/8 coming out of the fire wall which one goes to the manifold and the other to the water pump.

 

Also switched to a carburetor.

 

5/8" is the hot water coming from the hot place on the motor (top of the intake).

¾" is the cooled water coming back from the heater core after it heats up the cabin air. It goes to the cold side of the system; either a port on the radiator on the pass side, or the hole on top of the water pump.