[Cherokeetribe]

2001 Jeep Grand Cherokee. Heater is blowing cold air! Both heater hoses going in and out of core are at normal (hot) temps, blend doors functioning properly, coolant levels good, no air pockets in system, air flow control working properly... Any further advice much appreciated!

 

[Shark_13]

If both heater core hoses are hot, and you have good air flow, is likely the blend door. They can break inside

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[superj]

yup. also, you hit the wrong area for your post so i am not sure how much help you will get. this is the xj section for the square small Cherokees. you need the wj section

 

[ColdCase]

If the blend doors are working properly, there are no other air blockages, and both heater hoses are hot, then you likely have a partially plugged core. There is enough coolant flow to warm the hoses but its only going through a small part of the core and not transferring much heat to the air. Not sure about the WJ, but on some other models with notoriously narrow core passages, reversing the hoses at the firewall sometimes pushes the clogs out of the way enough to provide heat. Otherwise a coolant flush may help, often you end up replacing the core. But, as mentioned, the blend door or actuator is often the cause.

 

[Bigrigr]

Agreed, back flush the heater core if your sure the blend doors are working properly. Is this the dual zone climate control? Or the standard heater? If standard, it uses engine vacuum to control the heater. Check for vacuum leaks under the hood.

 

[Cherokeetribe]

Thanks for that. First time here

 

[Itkonen]

Symptoms sound just like I had in my WJ and WK. Both had a clogged heater core. I used STP Coolant cleaner, drove engine to temp and then 20 minutes. After a while drained system. And refilled with water. Drove a day, did that again. Then 3 drains and refills and flushing with water hose all I could. And after that drained and put in proper Mopar coolant. And still, not a good heat in either Jeeps.

Disconnected heater hoses and flushed 2 hours backways and forth with 5% Citric acid and water mixture using a drill pump. Got a LOT of **** and rust out of both. And have now nice heat.

 

[three_jeeps]

Agreed, back flush the heater core if your sure the blend doors are working properly. Is this the dual zone climate control? Or the standard heater? If standard, it uses engine vacuum to control the heater. Check for vacuum leaks under the hood.

100% agree, core is blocked - disconnect hoses and backflush, perferably with a cleaner. You *really* don't want to replace the core unless you have to, unless you enjoy spending a 10hrs+ disassembling and reassembling the dash...