I have a 1999 Jeep Grand Cherokee 4.0 L6 147,000 miles that overheats when idle but when driving it goes back to normal. I’ve literally replaced thermostat, thermostat housing, radiator, has fresh and flushed coolant, AC blows cold it’s only when I come to a stop and it’ll randomly shut off but when I’m driving it’s ok. What could this be Ive done so much to make sure my cooling system doesn’t do this but yet it want to be stubborn.
Sounds like you fan assembly isn't kicking in
Does it have electrically controlled fans? Fan clutch? We had a Nissan pathfinder that overheated like that at stops, especially if you ran the AC. The fan clutch was bad, and the Chinese manufactured replacements were garbage. Our mechanic installed an accessory cooling fan that switched on when you ran the AC. It solved the problem.
IF it's like the same year "regular" Cherokee 4.0 it has both an engine driven fan with a thermostatic fan clutch as well as an electric fan. Both need to be working for proper cooling, especially at idle. (If the fan clutch stops working the engine-driven fan might look OK but it won't spin fast enough to provide airflow.)
You need a new fan clutch. Rock Auto - Hayden #2736 - $38.49.
The mechanical fan still works I was think maybe it’s the electrical one
You can't tell by looking if the mechanical fan is working. It will still appear to spin if the fan clutch is bad but will not move enough air. I had that problem on an old AMC Eagle, when the fan clutch went bad the fan looked like it was still spinning but the car would overheat in traffic.
The fan clutch is very likely to be bad on a vehicle that's over 20 years old. You should check the electric fan as well. They both need to be working.