PJ_Hunter

So my jeep was giving me issues with the heater only blowing warm to slightly above cool air when using the heater or warmish air while using the recirc setting. Folks said to replace the blend door. Which I just got done doing. and yeah, the foam on the OEM doors was dry rotted and not sealing.

But now that I have the doors replaced and the duct all sealed back up it's still not blowing hot air. The hoses to the heater core are hot and the one coming out is slightly cooler, I flushed this spring.

Any ideas. It's a ***** to drive on my commute which is approx an hour one way to the office.

PJ_Hunter

Nobody has any idea as to why I am not getting hot air?

dave1123

Do you have the dual climate control or the manual heater?

PJ_Hunter

Dave, It's a single zone heater. Blend doors and motor are functioning normally. Recirc finally started to blow warmer air after a 30 minute drive but as soon as I switched to panel/floor vents it cooled off.

Could this be a bad T-stat? Water temps fluctuate between 210-220

dave1123

One thing I've discovered is if the outside air is extremely cold, it warms better on a lower blower speed, thus giving the air more time to make the heat transfer. IDK if this is part of your problem, but this has happened to me. In my case, recirc made it really hot after a couple of minutes. Now I'm talking a sub-zero air temp. In your case it may be the fins of the heater core are plugged with debris, leaves and pine needle to name a few things. Anything that can get thru the cowl vent slots. Usually that stuff winds up in the blower motor. If you have a cabin air filter, remove it.

PJ_Hunter

How do I know if I have a cabin air filter? And the heater core, is that the metal object that I saw when I made the cut to replace the blend doors?

PJ_Hunter

Never mind the question regarding the cabin air filter. I found where it should be. I'll look when I get home, but I'm getting good air flow

jeep58

Just today I disconnected the heater core hoses on my 2000 4.0 jeep ran water thru the bottom hose flushed core out, then took some prestone radiator flush poured some to to hose till it came out of other hose clamped hoses up high so solution wit not drain out, them flushed the core again, hook hoses back up and ran engine with rad cap off, observe the air bubbling out the rad, also heater running full had to keep racing engine up till all bubblies expelled, heater is hot now. I think it was mostly air in the system. Still question thermostat, when running the engine the water never DROPPED off like the thermostat open, also gauge heats up and does not drop off after engine reached operating temperature!

dave1123

IDK what thermo you have in it, but The reason I like Stant SuperStats is because they open gradually and don't give you that rush of cold coolant thru the system. The flow thru the heater bypasses the thermostat anyway. When the thermostat is closed, the only coolant circulation is thru the heater core.

The best way to get air out of the heater core is to make sure the hose from the thermo housing goes to the LOWER pipe on the core. That way air bleeds out thru the water pump naturally.

PJ_Hunter

Probably plain ol' OEM. I'm at a complete loss here. I have great air flow. Not overheating the vehicle at all. Hoses to and from the core are hot.

dave1123

OH...Wait! I just had a brain fart! I wonder if the blend door actuator is timed right to open the doors properly. It's a stepper motor and I'm not sure if there is a procedure to get it installed correctly. The blend door's function is to blend outside air with heated air to control temperature. Give me a few minutes to check my FSM.

PJ_Hunter

Yeah, but I was having this issue before I swapped out the blend doors from the ones that another user posted in this forum.

dave1123

No, nothing specific. I guess it automatically aligns where it should. Bummer! I thought we were onto something.

That's about all I can think of. Sorry.

PJ_Hunter

Any other folks with some ideas??