I have a 2001 XJ sport. Apparently the motor was swapped out with a Grand Cherokee 4.0L because I noticed the a/c compressor was on opposite side of the motor and my water pump matched a grand cherokee 4.0 vs an XJ 4.0...Anyways, I had an overheating issue at idle and ended up replacing the water pump and thermostat. I knew I had a leak at the radiator so I replaced it yesterday and drove it to work today. Temperature was normal the whole way to work but after sitting in parking lot for around 45 minutes with motor running, it spiked up in temp and started to overheat. I know these cherokees commonly run hot but I have two electric fans that run off of the ignition so I don’t understand why it’s overheating at idle. I have checked the coolant and oil, but there are no signs of a blown head gasket. Any thoughts or advice would be greatly appreciated!

 

I should also add that after replacing the water pump and thermostat due to overheating at idle, the XJ seemed to run fine at idle for any amount of time but due to the leak I had at the radiator, I replaced the radiator and once again it is overheating at idle. I know I need to get hood louvers to help the trapped heat escape but I just can’t figure out why it would overheat at idle after replacing the radiator. I rewired the two electric fans for a cleaner route and better splice job and the air is pulling into the engine bay which I believe is the way it should be rotating. Hope I’m not making this more difficult than it should be.

 

Has the cooling system been properly bled? So you don't have the mechanical fan anymore? And your electric fans both work properly?

 

Yes, I bled the coolant system properly and it has two electric fans, one of which replacing the mechanical. Both fans are wired to turn on with ignition and work properly.

 

Blown head gasket, Check your coolant for exhaust fumes.