Hi everyone,

Im having problems with my 2002 3.5 TJ (auto gearbox). Recently it started to overheat quite noticeably I took it to a mechanic ended up paying $350 to service radiator (acid pressure clean) also changing the thermostat. I thought it was fine but after few days same thing, temperature gauge will go way past the middle. After some observing i realized that fan is not turning on when it should, too late or even not at all. It does work but just too late when temperature already staring to rise past the middle, it never used to do that. Also few times it went nearly to the red & it didn't turn on.

Im pretty sure fan is alright because as soon as i turn on the aircon both fans turn on & the car cools down immediately So my question is what does control the fan to turn on when the temperature is rising because clearly that device is not working properly, thing is it actually does work properly sometimes. Im i looking at a lot more $$$ to fix this?


Thanks

There is a switch in the bottom of the radiator which monitors the water temp. (If its in the same spot as a gen 2, it is on the driver's side) Check that the plug hasn't come disconected.The fans are obviously ok - short term solution is to turn on the air when the temp creeps up.

I wonder if your elec plugs are fully connected. Check dud relays or fuses. May be paralled fusing for the radiator fan when the AC comes on? Is the thermostat wiring intact?

Damn, 350 to service the radiator is bad... a new alloy one is only $200ish

You have a cracked block, you will need to purchase a new engine, you also have cracked heads so a new heater core will be needed (just thought I would beat everyone to it for a change lol)

Now seriously, first of all check your fan switch, if your fans come on with the air con, then the fans are fine. If this is ok, then check your relay in the engine compartment box. Easy way to check is swap the fan relay with the aircon relay, if the aircon does not work the relay is fried. The relays in the third gen are generally pretty reliable but that having been said anything can wear out.

If the car cools with the air con on, you can eliminate any issue with the cooling system itself and point to the cooling fan area

mmm would it not just be a broken heater core? leaking coolant out and therefore overheating?

There's actually three Radiator Fan Relays for Lo, Mid and Hi, check under the Fuse cover in the engine bay, and replace where necessary.

Hi everyone,

Im having problems with my 2002 3.5 TJ (auto gearbox). Recently it started to overheat quite noticeably I took it to a mechanic ended up paying $350 to service radiator (acid pressure clean) also changing the thermostat. I thought it was fine but after few days same thing, temperature gauge will go way past the middle. After some observing i realized that fan is not turning on when it should, too late or even not at all. It does work but just too late when temperature already staring to rise past the middle, it never used to do that. Also few times it went nearly to the red & it didn't turn on.

Im pretty sure fan is alright because as soon as i turn on the aircon both fans turn on & the car cools down immediately So my question is what does control the fan to turn on when the temperature is rising because clearly that device is not working properly, thing is it actually does work properly sometimes. Im i looking at a lot more $$$ to fix this?


Thanks

Need new big fan motor its gone

Both fans are running on aircon remember

mozzaldinho, was only kidding mate

Check relays, just swap them to aircon as you know that one works and if you pop a relay into the aircon and aircon no work relay stuffed

Just removing the plug from the temperature pickup on the radiator, shorting across the 2 contacts in the plug with the ignition on should fire up the fans if the relays are ok.
Had this problem myself, but in my case both fan motors had died. Trip to the wreckers and $45 later all ok.

Both fans are running on aircon remember

mozzaldinho, was only kidding mate

Check relays, just swap them to aircon as you know that one works and if you pop a relay into the aircon and aircon no work relay stuffed

:rant: lol

Thanks for all the input guys, i will check relays this weekend untill then i will drive with aircon on at all times. Also i did put i "self made" CAI, basically a duct just going straight down to undeneath the front bar, is there anything i could have damaged while installing it?

Quoting MadMax "switch in the bottom of the radiator which monitors the water temp"

What does it look like?

Regards

A connector with 2 wires coming out of it - can't miss it if you get your head under the front of the car.
Your CAI - does it go in front of the radiator? Temp sensor is at the back of the radiator, at the bottom. If your CAI goes behind the radiator, you may have dislodged the wiring.

Yes indeed its behind the raditor i will have a look asap. Thanks for that.

Regards

I thought id revive this thread because two years on i actually fixed the problem. Anyways it turns out it was my Ipmco LPG Mixer setup that was interfering with the ECU & would not let fan to switch on when needed, so for past two years i had to switch on the air con to force the fan to work. I recently put it EMER VSI system & the problem is gone. By the way i dont think it was Impco's system fault most likely just poor installation by the fitter.