Ok so here is an interesting one.

Things I have replaced:

-Engine (complete overhaul - new cyl head)
-Water Pump
-Both Radiator Hoses and lower heater hose (upper is clear of debris but still factory)
-Thermostat
-Heater Core (specter)
-Evaporator Core (4seasons)
edit: - I also have a new radiator!

Sitting in a service stall, bleeding the coolant I was able to get MAX 150F at 2000rpm. Its steady around 120-130F at idle. Today was especially cold in wisconsin and on my way to work it never broke 110.

I thought I had it all figured out but im stumped. Blend door is working properly, and mode doors cycle properly. Although I can't confirm the mode or blend doors fully and completely sealing, I can see them all actuate.

I need more heat! Anyone have any ideas?

 

It's not all that interesting and a common problem. Your temperature is too low for a 4.0. It should run around 210. What thermostat did you use? If not OEM 195 degree, you should pitch the one you bought and buy a Mopar.

 

How did you manage to keep your 4.0 at 110 degrees while driving?? I feel like most of the time mine wants to get up to 400 degrees if it could.

Underheating issues are almost always thermostat related.

 

Maybe I should have clarified a little more (even though im still confused how we got on the subject of engine temps). I mean heater vent temperatures! My engine temperatures are nominal from 185-200 right now in the winter. My VENT temperatures from my heater are the ones not optimal.

 

Flush the heater core?

Feel the heater hoses with your hand and see how they compare in temp to the radiator hoses.

 

This changes things. I would suggest you first reverse flush your heater core using this method:


And then chemically flush your entire cooling system with a quality commercial radiator flush system.

 

OP said the heater core was replaced

 

Indeed. Core was replaced, and while I was in there I found my evap core leaking and severely clogged. Replaced that as well.

The only thing that is old is my larger-of-the-two heater hoses. Yet I cleaned that pretty rigorously before reinstalling after the engine overhaul.

After the engine warms up both pipes get pretty hot!

Service manual says at 60F ambient I should be at minimum 144F at the FOOT vents and 153F at 90F ambient . Seeing its not 60F or 90F, one can tell the difference of the those two temps is 9F, so at 0F ambient you should have a minimum of 126F. Although my temps ALMOST reach the MINIMUM of these temps, I really feel like something is off. There just needs to be more heat!

 

I'm in the same exact situation. Can hear the blend door closing. Like a noticeable thump. Not sure if it's sealing though. I even tried tapping on the little lever the cable connects to and it won't close any tighter. Outside air is coming from somewhere. The 01 my wife drives will nearly burn you the heat blows so hot no matter how cold it is outside. Dreading pulling the dash apart but it's looking like my only option. Not having a headliner or carpet just makes things worse. I think it was ccken who had some pics and diagrams of the whole system including ducting up on a thread somewhere.

 

These guys claim to have a blend door fix that doesn't involve having to take the whole dash out. No idea how well it works, so caveat emptor:

http://www.heatertreater.net/magento...kee-97-06.html

 

That's very interesting, Anyone tried it?
Ours are about the same with heat output.
Had a blazer with same problems as the video describes, and now 2xj's

 

You should try it, document it with photos and results, and post it here.

 

I hear youre the guy to go to with Jeep problems. Any inkling as to where my problem may lie?

I think I may start with completely verifying my blend and mode doors. The only reason i felt slightly confident in their operation is because when I opened the HVAC casing I was able to see the blend door completely diverting to the heater core, since I had it on completely hot before removing it. When I put it back together and moved it to cold, it moved enough for me to reasonably assume it made the full-almost-180 turn to divert to the cold side.

Im still stumped. Pathetic heat out of an almost all new system.

 

I'm more into the early stuff.

A blend air door issue could surely cause you're problem though.

 

Thank you, sir. Definitely going to look into it. Im also wondering if my clearwater cylinder head has a restricted port for the heater hose that I haven't fully confirmed yet either. That may be another day since ill have to take that water neck off though.