Jeep Wrangler Forum banner

2003 tj heater issues?

1K views 10 replies 4 participants last post by  scorro 
#1 ·
Ok this one has me baffled?
I flushed my heater core and radiator thoroughly.
Refilled the radiator and even burped it properly.
Have checked my actuator switch and it's working fine.
The heater vent door opens and definitely closes ok.
WHY THEN WHEN I TURN THE HEATER ON DO I ONLY GET HEAT BLOWING THROUGH THE VENTS FOR ABOUT 30 SECONDS AND THEN THE AIR COOLS?
I LEAVE IT OFF FOR A COUPLE OF MINUTES THEN TURN IT ON AND I GET HOT AIR ONCE AGAIN FOR ABOUT 30 SECONDS THEN THE SAME THING HAPPENS?
Does anyone have any idea what the hell is wrong with this thing?
I mean if the heater core is shot then why do I get heat for 30 seconds or so and then it cools down?
It wouldn't be that bad if it wasn't in the middle of winter!
 
#2 ·
Either the air flow is not going thru the heater core or the heater core is not getting enough hat coolant flow

If the flow is minimal when no air is blowing thru that minimal flow still heats up the core so the first air thru is warmed but once the air flows a while it has taken away the cores heat and the hot water flow is insufficient to keep the new air warmed

Same as a diet and exercise program calories in vs calories out if the heat calories supplied by the marginal flow is less then the calories carried away by the air flow the core and the air output cools

Easy way to check is to determine the temp of the return line from the core to the engine if its temp is dropping quickly as you run air thru the heater core and is no longer too hot to hold you found your issue
 
#5 ·
Did you take both heater hoses loose and back flush the core? I had same issue after a radiator flush and it was the heater core stopped up. After flushing just the core all is well.
 
#7 ·
Since it was all working just fine before you performed the maintenance, I would guess you have a pesky air bubble in it. Jack the front up as high as you can (or park on a monster hill) and run it with the radiator cap off for awhile and see if it will eventually take more fluid.

The only other things, outside of a random coincidence of something breaking the exact time you decided to service your cooling system, is that your high flow thermostat has a bypass hole in it. I put one like that in my Mustang and it takes FOREVER to come up to temp now, however, once it gets there (including engine oil) it makes "normal" heat on a consistent basis. If the engine oil and everything isn't hot I can actually cool the core down and have to let it "rest" until the heat build back up in it. I hate that thermostat and it will be coming out ASAP.
 
#8 ·
You hit the nail on the head!
I ran the heater and checked the hoses running from the core and the one that runs to the thermostat housing stayed HOT but the other one running to the water pump cooled down.
How do I fix the problem?
Do I have to flush the core again for the 3rd time?
I flushed and back flushed it the last time and everything seemed ok?
Why is it still giving me grief?
As I said this only started after I put the new Hi-flow thermostat in?
How do I fix it?
 
#9 ·
You hit the nail on the head!
I ran the heater and checked the hoses running from the core and the one that runs to the thermostat housing stayed HOT but the other one running to the water pump cooled down.
How do I fix the problem?
Do I have to flush the core again for the 3rd time?
I flushed and back flushed it the last time and everything seemed ok?
Why is it still giving me grief?
As I said this only started after I put the new Hi-flow thermostat in?
How do I fix it?
Do I need to replace the Hi-flow thermostat with a regular one?
 
#10 ·
2003 TJ Heater Issues

You hit the nail on the head!
I ran the heater and checked the hoses running from the core and the one that runs to the thermostat housing stayed HOT but the other one running to the water pump cooled down.
How do I fix the problem?
Do I have to flush the core again for the 3rd time?
I flushed and back flushed it the last time and everything seemed ok?
Why is it still giving me grief?
As I said this only started after I put the new Hi-flow thermostat in?
How do I fix it?
Do I need to replace the Hi-flow thermostat with a regular one?
 
#11 ·
You hit the nail on the head!
I ran the heater and checked the hoses running from the core and the one that runs to the thermostat housing stayed HOT but the other one running to the water pump cooled down.
How do I fix the problem?
Do I have to flush the core again for the 3rd time?
I flushed and back flushed it the last time and everything seemed ok?
Why is it still giving me grief?
As I said this only started after I put the new Hi-flow thermostat in?
How do I fix it?
Do I need to replace the Hi-flow thermostat with a regular one?
As a last resort I would pull the thermostat and see if you get heat then. That would tell you if it is a thermostat issue.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top