View Full Version : overheating - cooling fan not coming on

October 11th, 2017, 07:40
I have a 1999 xj 2 door 2wd i6 4.0

It overheats quickly at idle and in traffic.
Light comes on. (No gauge)
It boils over into overflow tank.
Electric fan never comes on to assist with cooling.

New parts I installed:
Radiator and cap
Temp sensor on therm housing
Electric Cooling fan
Cooling fan relay (black fuse box passenger side engine)

Fan will not come on even when i turn on AC ( doesn't cool anymore)

Any ideas?

October 11th, 2017, 08:42
Also... The cooling fan fuse located near the relay looks fine.
Unless it's a bad wire / connection what else could it be?

October 11th, 2017, 09:04
Test the fan and test the relay!

October 11th, 2017, 09:08
Also... The cooling fan fuse located near the relay looks fine.
Unless it's a bad wire / connection what else could it be?
What year XJ? The electric fan controls are not not the same throughout the model run.

It could be a bad fan relay, a burned out fan or the computer isn't turning that circuit on, along with possible bad wiring.
It's time to do some troubleshooting, get your voltmeter out and start tracing the power pathway, starting either from the fan, and working backwards or at the battery and working toward the fan.
A wiring diagram, from the FSM for your year XJ, makes this process a lot simpler, more productive and less frustrating .

My XJs have manual fan bypass switches, allowing the electric fan to run continuously, if desired. You might try installing one.

October 11th, 2017, 10:41
1997-2001 you can test the e-fan function by carefully disconnecting the wire plug from the Coolant Temp Sensor on the thermostat housing while the engine is running. If everything is functional, about 5-10 seconds after the wire plug is disconnected, the e-fan will start and run. The Check Engine Light may come on, but will go out by itself after reconnecting the wire plug.

If you are overheating at idle, you likely need a new mechanical fan clutch. The fan shroud is installed, right ?

October 11th, 2017, 12:37
It does have shroud. I will have to try unplugging the sensor while running when i get back home tonight. See if that starts the efan.
It doesn't take long at all to boil over.
As soon as it gets to temp.

October 11th, 2017, 13:37
You mentioned the ac doesn't work.

Unplug the electrical connectors from the back of the compressor. Then turn the ac on and see if the fan comes on. My understanding is sometimes the low pressure switch on the ac messes with the e fan coming on... but I could be wrong.