I bought my 98 Cherokee few months back, had some cooling issues but I think I got em figured out l. It was puking coolant out the reservoir and trying to overheat. I did a flush with that stuff you buy at the parts store, new thermostat and cap and fixed the puking problem runs cool as can be. I did turn on the heater full blast while I was letting the Jeep run when I was doing the flush. I was told that would help clean out the heater core but idk if it helped or not because heater is blowing as warm as it should be!! Any help would be appreciated!!!

 

Heater core could be real gunked up. Search for "reverse flush". Also make sure the control module that allows the hot coolant to flow through the heater core is operating at 100%, and not just barely opening only allowing a little bit of hot coolant to the core.

Look at this thread for location of valve

https://www.cherokeeforum.com/f2/new...s-again-29877/

keep the heat off and pay attention to the orientation of the metal arm, then go turn the heat on and make sure it looks like its moved to open the valve. And then you can check the temp of the hose that goes to the core and see if its getting real hot, or luke warm. If its just warm, valve may not be opening all the way allowing a lot of flow

 

This 98 doesn’t have that control valve, the heater core hoses just go from the fire wall to the therm and water pump!!!

 

DOH!!!!

Blend door issue then maybe?

 

or maybe some gunk came loose and now its got restricted flow........?????

Check that reverse flow flush option...

 

Guessing reverse flush would be the bottom hose “water pump” through the core and out the top hose “thermostat” ???

 

I checked the heater control **** on the dash when you turn it seems to open fully underneath the dash on passenger side!!! Is that the blend door??

 

I'm not a reverse flush expert, never done it just read about it a little on here. So I'm sure a quick search would bring a good write-up about it.
By Blend door I mean the door that opens and closes to either let in hot air or cold air, whichever setting you have the control panel set to. If you have it on cold, then go to hot, its supposed to shut off the cold air flow completely so only hot air comes out. Its controlled by vacuum lines. So maybe you have a vacuum leak and its not able to close off cold air completely.