It's getting colder in the morning. When using the heat at idle and the engine fully warm, the heat is only luke warm at best. The heat gets warmer when driving at higher RPM's but it's not as warm as it should be and it just cools down when the RPM's drop. I just flushed out the coolant and changed the thermostat. I had my shop perform a pressure test and there was no leak. I've been smelling coolant since I bought my XJ (8 months ago). I though I might have a bad Heater core but I'm not sure. The temp gauge read normal all the time and does not drop or go higher them haft way. Does anyone have any ideas?

 

Did you check to see if the hoses going into and out of the heater core are getting hot?

 

I have not. Should both hoses be hot?

 

With the engine fully warmed up they should be hot with the in at 20 to 30 degress hotter than the return. Hot enough that you would not want to hold on to them. If you have a lazor temp gun you check without trouble.

 

If there not getting hot, what does that mean? Sorry, I have not idea how the cooling system works.

 

Both heater hoses should feel about the same temperature. When checking this see if you have a water valve, it could be stuck closed.

 

Heres the deal. If the engine is hot (around 210) and the hoses are warm then you have a plugged up heater core. If you follow from the heater core back to the front of the engine just above the water pump you will notice that the hose temp will be higher if not actually hot. When the coolant can't flow through the core it just sits there.
Anyway , if they are indeed HOT, then you have a blend door issue inside your heater box, if it does not close all the way you end up having to much cold air mixed with the warmed air from the heater core, but you did say it would get hotter when you were moving along so I believe it may be a plugged heater core.

 

Cool, thank you Willys55 for the help.

 

Your Welcome, we are all very pleased to help.

 

I FIXED IT, YAY. OK, so I flushed the heater core with a garden hose. LOTS of crap came out, mostly rust. I forced water into both hoses one at a time, back and forth until the water came out completely clear ( 8 times each ). After I was done, I reinstalled everything and topped off the antifreeze. The heat now comes out extremely hot all the time. Thanks for everyones help.