Hey Guys. I've done some searching on this and have tried different things, but with winter approaching I would like to get this figured out.

I have an 80 RN37 it is still pimping the original 20r. When I bought it someone had put a Weber on it, disconnected all vacuum hoses, and other things. What I know is Heater core is not clogged, valve on firewall is good. but I get no heat in the cabin.

drivers side of truck I have:

Lower radiator hose to metal U pipe which has a 2 lines coming off of it, one to water pump and little one to firewall/heater core. note: block off plate on backside of water pump.

passenger side starting at heater core I have:

heater hose going to Heater Control Valve, then to metal pipe under intake plumbed into back of water pump. then I have upper radiator hose going from water neck/thermostat to upper radiator.

I have one other heater hose that is looped from top of intake behind carb going to metal pipe also under intake that terminates in valve pancaked in between intake and head.

I have hooked heater hose into valve behind middle of intake with same results.

I have burped system, confirmed flow through heater core, and control valve. its almost like I'm pushing water into both sides of heater core and its just sitting there. from what I understand water travels from drivers side water pump lines? any help would be greatly appreciated.

 

From what I got from EPC looks like it is supposed to go to pipe that goes into head behind intake. The one its hooked up to is the water choke lines. PO had it right I think. Still had no heat that way either. maybe fins on heater core blocked real bad???

 

How sure are you it is not clogged? It is not that bad of a job to remove and check/clean, and let the inside soak in CLR or rad flush product. It may or may not solve the issue, but it sure will help. I think even if the fins were clogged you would still have some heat.

 

Thank you for the reply Gilles de. I ran water through heater core with no restriction. I switched 2 heater hoses back on passenger side, and burped system again yesterday morning, drove it about 20 miles and checked heat, low and behold it was blowing hot at windscreen, and small floor vents. Read glove box manual and realized heat will NEVER come out of center vents.

The blower motor sits above heater core, center vents sit in front of blower motor, therefore air coming out of center vents never passes through heater core radiator fins. Air that is channeled through heater core will ONLY come out of defrost vents and floor vent. truck with AC are ducted a little different but still no heat from center or outer vents for them either. If truck was never equipped with AC like mine outer vents are ducted to the cowl box behind windscreen and will ONLY blow outside air even when recirculate is picked over fresh air at heater controls.

So in conclusion I probably had heat the whole time. for that I apologize for the post.

How I get heat out of my 80 4wd is this:

Turn round outer dash vents sideways to close them
Set vents to either Defrost, or Heat(go figure)
Set outside Air to recirculate (you can keep on Fresh setting if big hose is still plumbed under passenger dash board. If its not there Fresh will dump cold air from cowl box into passenger side floorboard)
Turn on Blower

and that should keep you toasty if system is functioning properly.

M