Radiator problem just warm heat

[jt1776]

I have a 1969 C-20 that has a turbo 400 trans that I think I have it hook up wrong. Will the person I bought it from did. The top hose on the heater core goes to the water pump the bottom hose on the heater core goes to the manifold. There isn't any hose going to the top of the radiator. That line out is just plug ed up with a rubber hose. And the big hose goes to the bottom of the radiator. I do believe the trans line are correct because it drives fine except that the kick down switch isn't hooked up the wire is just hanging. Thanks I need the heat bad Its cold up here in Michigan.

[cdowns]

a couple things that can cause poor heat// low temp thermostat or no thermostat// the box that the heater core is located in is clogged up with 40years of crap not allowing proper airflow for heat

[jt1776]

I am going to clean that out but are those hoses on right? I have a manual for a 72 gmc the picture it shows is the top hose on the heater core is going to the top of the radiator. I thought that was for the turbo 350.

[Zeke's Garage]

As long as your coolant level is full, it really shouldn't matter which hose on the heater core goes to where... but ideally, I've been told, that the pressure side from the manifold should go to the bottom of the core, and the return should go into the water pump. This keeps the core as full as possible, allowing heat transfer from the fan.

If you aren't getting hot air from the core, double check that your thermostat is installed and working. Then check the air plenum around the core, the cowl fills up with crap really fast and can choke off air flow. After that you may need to flush the core as it could be plugged and not allowing any circulation of coolant.

Good luck

Shawn

[LockDoc]

If the heater hoses are hot I'm bettin' on mouse nest in front of the heater core, stopping air flow through the core. You have to take the outside housing off to get it out. If you have to do that you may have to drop the inner panel on that side to get to the fasteners on the bottom of the housing. There are some threads on here about it.

LockDoc

[jt1776]

thanks for the help i just bought a new heater core and I am going to flush and clean the system I want good GM heat. I will post tom if it works

[swamp rat]

I also have a 72 and my return to the radiator actually on the bottom of the core yet Everything i have read says to have the core bottom the inlet and the top the return so it fills from the bottom. the core inlet and outlet are different sizes so i was guessing that maybe someone at the factory may have installed some of the cores upside down?

In your case the line leaving the manafold is a positive pressure and should be feeding the core and should go to the bottom, the top should return back to the right side of the water pump just above the lower rad hose, or if you do have a return port on the radiator it can go there..

Some trucks didn't use the radiator for a return and had no port so they returned back to the water pump.

EDIT: +1 ^, Take both hoses off at the engine and shove your garden hose into the end of the large heater hose and turn the faucet on slowley and see if it pushes crap out of the core. Also you may want to concider pulling the cowel and wipers and cleaning out the heater intake from 40 years of crud buildup.