[nick.94]

Hi guys
New zooker
I own a 99 jimmy and it's a great little car, however it has been having some issues of late with cooling.

It would get hot and conk out after being laboured in the bush, and has also happened in traffic on hot days.

Radiator is in good nick. Has been flushed numerous times and filled with new coolant. I also changed the thermostat to no avail and today I replaced the fan clutch as we found the old one was not doing all that much.

After putting the new clutch in it's definitely better but it's still getting hot in the bush. It cools down quickly enough as soon as you start descending, but the main issue I think is the thermo fan which controls the AC is not kicking in to assist in cooling the engine. Thats what this fan does doesn't it?

If the car overheats and stops and I leave the ignition on the fan will kick in and run until the engine is cool. However it will not do this when the car is running and the temp is climbing.

I have taken the sensor out and put a lighter to the bottom of it and as soon as it gets hot enough it kicks in.

Is it possible the sensor is dodgy and is only working when the temp is too high?

Engine is strong and has 120,000kms

I'm not sure what else to replace so would be extremely grateful for any advice!
I've exhausted my little mechanical knowledge

Cheers
Nick

[MrRocky]

Replace the radiator, flushing wont do anything the only way to properly flush a radiator is to remove the end tanks and rod the core to clean out blockages, something not really acheivable with plastic tanks

[fordem]

The thermo fan is there to improve airflow through the a/c condenser, it's really not intended for engine cooling at all, although if fitted, it will be used for that purpose, and you can test the sensor/switch by placing it in a pan of water with a thermometer and slowly bringing it to the boil.

The symptoms described are those of a defective fan clutch and/or a partially clogged radiator - which may clogged either internally (coolant flow) or externally (air flow) - if you have large spot lamps, winch, etc., these may also restrict air flow

Question - what transmission do you have - if it's an automatic you may want to consider an external transmission cooler - the stock one is in the bottom radiator tank and when the transmission heats up due to traffic or being pushed hard the coolant temps also go up.

[sideways]

My AC fan never came on when the motor got hot, I don't know if it's meant to.

Is the system holding pressure? Tried a new cap? Give a hose a squeeze (cold) and see if anything comes out the overflow.

I see there's now thicker than standard radiators on eBay, they cost a little bit more but I'd buy one of those for the peace of mind.

Fwiw G13bbs are prone to cracking heads and blocks if overheated.

[shep]

I would replace the 18 year old radiator 99% guarantee that is your issue.

[MrRocky]

If the standard rad lasted 18yrs as shep mentioned just get another stock replacement and replace youelr thermostat with a genuine one at the same time

[nick.94]

Thanks Guys.
Has a brand new genuine thermostat.
The thing that has me confused is why the thermo fan suddenly kicks in after the car has gotten hot and engine turned off. Then proceeds to run for a few minutes while the engine is cooling down...

[shep]

The thermo is for the AC and not engine cooling.