I must be going crazy but I can not for the life of me find the port for the outlet heater hose. the one that comes out of the firewall for the heater. the inlet I know is on the intake mani but I thought the outlet connected to the water pump, but theres no where to connect it.

 

The heated water comes from the manifold (or, manifold to throttle body - TPI) and connects to the heater control valve. From there it is routed to the heater core, or bypassed if hvac set to cold, and returns to the radiator. The fitting for the return is just under the filler neck, pointing towards the firewall.

 

Thanks deadbird, I needed this info myself. Do you know if there is a check valve included in the routing (maybe in the control valve)? I just dont see how the water gets back into the radiator which is under pressure! The regular flow of water from the engine would be forced into the radiator through the water pump, but this flow would bypass the pump. Is it really flowing, or is it just sort of creeping through the heater system. I ask because I have put an 85 z28 TPI motor into a 36 Olds and am looking to use the system for both heat and a source for the original temp gauge sender. If I put the sender very close to the outlet of the throttle body, will I get a very accurate indication of the overall water temp?
Thanks,

Ron

 

When the thermostat is mostly closed bypassed coolant flows through that hose at a pretty good rate, at least several gallons per minute.
The radiator is on the suction side of the coolant pump. From the coolant pump to the thermostat is pressureized by the coolant pump, but its really not that much pressure like maybe 1psi maybe a little more or a little less. From the thermostat to the pump inlet is the low pressure side. The entire coolant system is under stadic pressure determined by the radiator cap and engine temp up to 20psi.

Depending on your set up you can have your return on the pump or on the cool side of the radiator. I like having the return on the radiator so that the transmission heat exchanger always has coolant flow over it. But if you live some where real cold you might want a pump that has a return on it.

 

Thanks oil pan 4. That makes sense. The whole system is under presure, so it becomes a relative presure issue. I was just looking at the parts houses for a heater control valve for an '85 Camaro and see that no one lists one. How is the water regulated to the heater core? Is always on and the blower control switch decides wether you get cold air or hot?

 

The later models have one of these:

http://shop.advanceautoparts.com/web...S_888737409___

Here on TGO we call it a Heater Diverter Valve - it gets a vacuum source from the heater controls, and so when the delector is on warm, the valve opens and allows hot coolant into the heater core - when selector on cool valve closes and no hot coolant runs through heater core.

But I don't see it listed for the earlier years either, so it may not have been an option until later. Do you have TWO vacuum lines coming out of the firewall where the blower motor wires go in, or just one? If just one vacuum line there, then it wasn't an option for your car, and therefore you just run a heater hose from one heater core end to the intake, and run another heater hose from heater core to radiator.

Most uf us got rid of that ugly heater diverter valve anyway 'cause we just didn't like them - I had one originally, but tossed that sucker in exchange for a cleaner engine bay.

 

In the older cars the heater core had hot coolant going through it all the time. To turn off the heat there was a door that blocked off air flow through the heater core to get cool air.
Remember you need a coolant bypass.