Engine Heating up

Hi peps,

I have been having overheating problems in my 2011 Jimny for sometime now. I have had to already replaced the radiator, water pump, the thermostat, the radiator cap and engine! But the problem persists!!

Basically, the temperature slowly creeps up when the car is stationary after it has been driving. With the previous engine, I ran into this problem on two road trips. When I slowed down in towns the engine would overheat. But it would also creep up to red after about 2 hours of driving. We had to pull over to allow it to cool. Suffice to say, the engine was eventually destroyed.

After the new engine (which was a few months ago), it has happened three times: once after going 90km/hr for about 15mins, another time after going 100km/hr for about 1 hour, and the latest after going 60km/hr for about 10mins. I have managed to keep the car from overheating by putting on the heater which results in the engine temperature stabilising.

I am baffled by it. I was wondering if anyone has heard anything similar or had suggestions as to the cause.

Cheers guys

Viscose fan coupling not working?
When I first start my car the AC fan will rotate quickly, but soon after stops or reduces to a slow rotation. This initial rotation is due to my main cooling fan viscose coupling still being engaged from the engine being run the day before (hot engine). It's air through the radiator driven by the cooling fan, hence the AC fan rotates in this air. The stop soon after is it responding to the fact the engine is cold,  cooling fan disengaged again until the engine warms up. 
The AC fan, which is not on by the way, is a tell tail of your viscose coupling operation and so main cooling fan operation. Just a simple one to check first.

Thanks man for your reply. So I am trying to understand it. My Jimny seems to have a viscose fan and an electric fan in front of the radiator. The electric is the AC fan? And the viscose fan is the general cooling fan? They both seem to be turning fine when I turn the vehicle on.

I did always suspect that the air flow was a contributing factor but didn’t understand how. I think it was always going but maybe not as fast as it should have been?

I have just tried sticking a cardboard roll in the fan at operating temperature and I was able to stop it without any damage to the roll. So should I say the viscose fan is broken?

Yes. It's possible to split the unit and replace the oil using silicone oil found in RC car dampers 6000 is about right. Or buy a new one.

Can't say for sure about cardboard roll, I've got a fear of shoving things into rotating plastic. It doesn't sound right, although viscose is never truly 100% coupled. It should have put up a bit of a fight as you stopped it. Worth checking further or get a used / new one as Lambert indicates.
just for clarity you are correct. AC fan is electric and is in front of Radiator. Viscose coupled cooling fan is belt driven on the engine side. From a cold start (after hot) both should turn, but after about 30 seconds the AC fan will stop rotating. That's how a cold start appears to me and a working system.

Just as a matter of interest where are you based and what is the ambient temperature?

I too suspect the fan, if it is okay when moving then it is the job of the fan to keep air flow across the radiator when stopped. However, you mentioned temperature creeping up whilst moving, so unless it is very hot where you live, I am starting to suspect a leak in the coolant system. you also mentioned putting the heater on stabilised it, so does sound like the radiator is not doing a good job.

Are there any signs of coolant loss, or is the expansion tank filling up?

Alternatively, is the space front and rear of the radiator clear? There isn't anything fixed to the front which is stopping air flow?

Here you go, the explanation of "how it works".
In simple terms the hot air from the radiator expands the bimetallic strip, this opens the valve and the fluid locks the fan to the drive plates (as it spins). Once cold the bimetallic strip closes the valve and the fluid stops locking the drive plates (as it spins), and the fan stops turning.
This is that you see from a cold start. The fluid is still in the drive plates from the day before but the bimetallic strip has closed as the valve is now cold. You start the engine and it takes a few rotations for the fluid to return to the reservoir, unlocking the plates and slowing the fan. The AC fan is just showing this as airflow.

 

I live in Queensland Australia so can get pretty warm. It first started around Rockhampton in the middle of the day (so around 40*C) on a road trip. But it was also happening in winter down south near the snow.

The coolant was leaking before the engine replaced. It might still be leaking but haven’t investigated. Somehow recently some mud got into the system too which had to be cleaned out (yes doesn’t help the situation). The expansion tank doesn’t seem to be overflowing though.

There is the AC fan fixed to the front of the radiator. But that’s it.

It does give somewhat of a fight but I wouldn’t have thought I’d be able to stop it. I might open it up and check it out.

Just not sure which silicone oil is the best one and is available in Australia that I can pick up. Any recommendations?

I used 6000 grade, got it from my local RC car shop, was less than a tenner for 500ml.