I have a 2001 Cherokee Sport with the 4.0L 6 cylinder motor. This is my first winter with the rig and the other day I noticed the heater isn't blowing cold air. I have tried to trouble shoot this a bit, all the fluids are topped off at the appropriate levels and when the car is warm the engine temperature is in the appropriate range. It seemed like the A/C clutch might not have been disengaging, so I pulled the fuses to the A/C system to take it offline but it still blew cold-warmish air. I figure it must either be the thermostat or the heater core. Anyone have any suggestions on the best way to trouble shoot this before I start taring my motor apart? Thanks.

 

Back flush your heater core several time and see if that helps.

 

Confused here.

What exactly do you want your AC/Heat system to do?

 

Try flushing out the heater core. There are 2 hoses that go from the firewall along side the valve cover and into the thermostat housing. Stick a hose into one and flush all the crappy out.

 

Make sure that the air blend door is operating correctly as well.

 

Thanks for the info, I'll try a flush first.

 

When you flush it make sure to flush it in both directions. When the water starts coming out clear give it a few more flushes in both directions. Once you are done let us know if it helps if not we can go from there.

 

I had that same problem in my "96. I just took the return side hose off the heater core at the fire wall, inserted a bike tire pump hose (with the end removed) and pumped hard a few times. It loosened the crud and allowed the fluid to flow through the heater core. Problem fixed and its been good for 2 yrs now.

 

I have the same problem with mine all of a sudden. Was working great a week ago and now it's warmish. Not hot. What's weird about mine tho is when I am driving it heats up good. When idling you can feel the temp cool down. I have noticed my temp gauge is a slight bit cooler than normal also. A few months ago I had replaced the thermostat and radiator. Did a flush on the system and added new hoses and fluid. Another weird thing it just recently did is my ac stopped blowing really cold too. I had just recharged the system a few months ago. Was working great. The cooler lines under the good are still ice cold tho. Just not in the cab. Anyone have any ideas? Lol

 

Do your heater hoses get hot to the touch?

 

this.

if BOTH arent hot to the touch, it confirms the heater core blockage.

i have to do flush my heater core on my 98 every winter for the last 3 winters, im too lazy to change it out.

warm the motor, undo the hoses at the motor, flush the core, pour the rad flush chemical in, let it sit, flush and reverse flush

 

Can I use the hose to flush? I read somewhere else the pressure could destroy the core.

 

Yes Sir! The garden hose should be fine unless the heater core is already bad and getting ready to leak. Not a whole lot you can do, If it leaks when you flush it was only a matter of time before it started to leak on it's own.

 

I used a spray nozzle so I could pulse the flow. Kept thing churned up that way.

 

yep

my hoses are put away for the winter, so i fill up the core with water and use my air compressor to blow it out

do it til it comes out clean