Heating Issue

[bucknut713]

1998 4.0 auto.
I just bought the Jeep a few weeks ago and the radiator was replaced just prior to purchase. Last week the heat started to blowout warm so I felt the heater core hoses and one was hot and one was warm. I did a backwards flush of the heater core and the heat started to blow hot again and hoses were hot.
Got in it today and after about 15 minutes of driving it started to blow cool air again.
Any thoughts on this?


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[Chasitek]

Do a complete flush of your cooling system. Maybe some gunk from the rest of the system has re-clogged the heater core.

 

[bucknut713]

Do a complete flush of your cooling system. Maybe some gunk from the rest of the system has re-clogged the heater core.

Alright I'll try that next.

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[bucknut713]

It did the same thing this morning on my way home from work. Started out fairly hot then after about 15 minutes get cooler.

 

[ballpark]

Is there still air in the system? Did you jack up the front end and give it a good burp?


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[bucknut713]

Is there still air in the system? Did you jack up the front end and give it a good burp?


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I'll be doing that today.

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[Big Red 1]

1998 4.0 auto.
I just bought the Jeep a few weeks ago and the radiator was replaced just prior to purchase. Last week the heat started to blowout warm so I felt the heater core hoses and one was hot and one was warm. I did a backwards flush of the heater core and the heat started to blow hot again and hoses were hot.
Got in it today and after about 15 minutes of driving it started to blow cool air again.
Any thoughts on this?


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Like other said, probably have gunk in your system and needs a good flush. When I done mine * today actually* I flushed the core back and forth between the top and bottom fitting. Did that until it ran clear and didn’t think anymore would come out and then put a air nozzle to it and man did the crap come out then. Probably done that about 10 minutes till nothing came out. Just blow it out with a air nozzle and throw the water to it between times to flush it.
Edit: also maybe get a rubber hammer and beat around the heater core on the firewall but not the fittings, just the firewall. Also with the air nozzle on the return fitting, cap your finger on and off the supply side on top and it’ll help blow some stuff out. I flushed mine 2 or 3 times with not much difference until I took a air nozzle to it.