Apologies if this has been previously answered, but I have searched for days.

My 2001 3.5 Tj has been spewing coolant out though its overflow. (182,000km's)
Rang a friend of mine who works for Burson spares, recommended to change the temp sensor/fan switch. Didn't help.
Old retired mechanic friend suggested the thermostat. So I changed that, and it also has not helped.
I've checked all fuses and relay's. All working fine.
And lastly, I had a major service done. Timing belt, hydraulic tensioner, water pump, platinum plugs. The mech also removed the radiator to inspect for blockage, found that it was about 20% blocked, and the top tank needed replacing. Done that.
And after having all this work done, it still overflows. The radiator is not overfull either, as it overflows without a top up.
The reason why I mention the relay's/fuses. The temp fans aren't spinning when she heats, although my temp gauge never goes above half (reason for the change of sensors). I have tested both fans, and they spin when connected directly to battery. Driver's side fan (smaller of the two) will spin when the a/c is on.

And I'm still scratching my head for a fix. I like my car, its a nice drive, effortless.

Forgot to mention, it overflows when the engine is switched off after my drive.

Try a new radiator cap.

Check the bottle is flowing both ways as often the get blocked thus coolant will flow into the bottle but when cools will not return to rad. Collapsed looking top rad hose when cold is another sign

Is common on older cars

Personally I loathe this rubbish of replacing stuff due to having nfi about the isdue

Magnas dont have a fan switch just for starters

Our other car had this issue. It turned out some twit had swapped the hoses going to the over flow bottle.
Swapping the inlet for the outlet meant that when the radiator heated up, it pumped water into the overflow bottle which simultaneously ejected the liquid it was containing onto the road.
When the radiator cooled, it just sucked air in from the top of the overflow bottle.

Basically that's what Mal described, but I didn't benefit from a collapsed hose to spot the issue.

Not sure if some apprentice or mate is having a laugh or low IQ or a mech that wants return work.

Hi Madmax, new radiator cap came with the new tank install on the radiator.

Thanks for your help Madmagna, It must've just been a temp sensor then.

Oggy / Madmagna, I have a new top hose, but will be checking the flow to/from the overflow today.

Will be getting an ecu scan as well, to check the error log to see if its not just a burnt out wire.

Will post results.

Switched off and overflow - sounds like a rad cap - the pressure only builds up when the fans etc stop - check the the cap has the right rating it should be the right PSI/Hecta Peter metric thing

Check the bottle is flowing both ways as often the get blocked thus coolant will flow into the bottle but when cools will not return to rad. Collapsed looking top rad hose when cold is another sign

Is common on older cars

Personally I loathe this rubbish of replacing stuff due to having nfi about the isdue

Magnas dont have a fan switch just for starters

Resurrecting this thread briefly.
My TJ Magna has just started to overheat from time to time. Because it's not consistent, I suspect either the thermostat sticking or a fan sensor. However as Repco charge $95 for a thermostat, I don't want to replace that just yet.

And what's this about Magnas not having a fan switch ? There must be a sensor. Er..where is it, please, someone ? I can see two sensors just behind the thermostat...a big one and a quite small one. Obviously one is the temperature sender for the gauge. Does the sensor report back to the ECU, which then turns on the fan ?

Resurrecting this thread briefly.
My TJ Magna has just started to overheat from time to time.

Just been through overheating with my TJ - was the thermostat - it was obviously getting randomly stuck.

but also had the same issue with the old TH - the radiator fan motor has 3 speeds, 1st the low speed burnt out - then the 2nd speed the car would heat u until the ECU detected overheat and turned an all the fans - so check your thermo fan turns on and off when the car is hot an at idle.

Thanks for your prompt reply, bb....I'll do that tomorrow.

Does the sensor report back to the ECU, which then turns on the fan ?
Correct. The ECU has a table of temperature thresholds to decide when to switch the fans on based on what speed the car is moving at and whether the A/C is on.

I looked at the car when it had cooled a bit and the top radiator hose was squished right in. Aha ! Not sucking back. And as the overflow bottle is just a single tube for in and out, I sucked on the tube to see if the bottle had crap in the bottom. No.

So I replaced the radiator cap and all day today it's been a perfect temperature. Interesting exercise. I was ready to label it a sticky thermostat or slightly inoperative fan, but the hose was a giveaway. Lucky I didn't cook the engine....it got quite hot for a while there, and lost 2 litres of coolant.
Total cost : $ 14

Great outcome