JPHunter91

I have a 98' with a 4.0 and a few weeks ago I replaced the electric fan because the old one was burned out. Everything worked fine untill a few days ago, now anytime it's at idle for a few minutes it goes in to the red, and when I'm driving the temp is usually around 215 or so. The electric fan won't engage but when I hooked it up directly to the battery the fan kicks on so I know it works. Any idea what could cause these problems?

freegdr

Clutch fan suspect for idle issue. Does fan come on with Ac on ?

jomps

Does the electric fan kick on if you unplug the coolant temp sensor at the thermostat housing?

JPHunter91

Doesn't come on with a/c. Or when I unplug the sensor

freegdr

Pretty sure fan only comes on when pressures/temps reach certain point .They changed how it works on newer models . Not realky sure when this change came into effect .

DieselD

Mines a 99. My aux fan kicks on when the temp creeps up (225?), when the AC is on or when I unplug the sensor.

Its possible your ECU isn't getting the right temp, thus not turning on your aux fan. But since the AC doesn't turn it on... maybe the fan's relay/fuse is bad? Or wiring?

freegdr

Now were getting somewhere so it must be 2000 and 2001 it changed...OP all fuses should be tested not just looked at confirm power in and out.

DieselD

Good point, break out the multimeter.

djb383

Efan is a/c pressure activated on '00-'01 XJs......it's compressor clutch engagement activated on '99 down. '98 FSM says at 218F coolant temp, efan on and off at 209F.

4wheeldrivenewbie

Ive had a similar problem in my 89 could just be a old clogged radiator. My fan doesnt kick on so when im at a light or traffic temps rise.

the relay tested good put in a new coolant sensor and still nothing happens. what could be happening is the lower part of the radiator near the sensor could be somewhat clogged up and not allowing coolant to pass threw the sensor properly.

id just spend 50$ on a new radiator if u have eliminated a bad sensor or relay or fuses. see what i had to do for a temp fix is hook up a toggle switch on my dash to the fan relay so now when i get stuck in traffic i switch it on.

i dont know about newer jeeps sensor placement as they have an open system and mine is closed

Pelican

'91+ do not have the switch in the radiator. Fan is controlled by PCM and A/C as noted above.

Where are you finding that $50 radiator?

freegdr

89 and 98 operate from different sensors just so ya no we have three 98 have one .

4wheeldrivenewbie

i here ya. This is what i found http://www.ebay.com/itm/BRAND-NEW-RA...268b8c&vxp=mtr no matter if u got 99 or 87 there all pretty much 50-60$ shipped not to bad sounding

4wheeldrivenewbie

ive herd of 2 coolant sensors the one located on the lower right side of the radiator has been replaced and the other one as well.

freegdr

The radiator one is coolant fan switch the other is coolant temp sensor on block then theres coolant temp sender on rear of head.