HZJ Overheating

[Mazzotti01]

I have for the first time ever since owning my N/A 105, had the engine temperature move out of the normal operating range.
This happened driving back form Albany with a full load (full roof rack, boot, and three adults), constant 110kmh with intermittent hills, and it was a 40 degree day.
I know that even with all factors taken into account, the engine should still not move out of normal temp range. I am thinking it could be a blocked radiator or bad thermostat.
Any tips or suggestions would be appreciated.

 

[Charlie]

Maybe it’s the fan clutch

 

[clivehorridge]

I’d go with the fan oil having evaporated or adjustment inside. The oil is available an OEM part number, or you could bite the silver bullet and buy a new unit.

I’d take the trouble to flush the rad anyway as a precaution and change the thermostat and rad cap while I was at it.

A new fan on mine was a revelation, I don’t think the old one had ever worked in my ownership, before.

 

[StarCruiser]

Is the fan going to be the issue here as at 110kmh there’s plenty of ram air cooling? Maybe the radiator core has an air restriction due to dirt in it? Bugs in the AC condenser maybe? Is the airflow obstructed by additional lights? Was the AC being used?

 

[Mazzotti01]

I’d go with the fan oil having evaporated or adjustment inside. The oil is available an OEM part number, or you could bite the silver bullet and buy a new unit.

I’d take the trouble to flush the rad anyway as a precaution and change the thermostat and rad cap while I was at it.

A new fan on mine was a revelation, I don’t think the old one had ever worked in my ownership, before.

Ok sounds like that could be it. If there is an issue with the fan clutch or oil, would that mean the fan is not running? Or would it just not be running at a high enough speed?
Cheers,

 

[Mazzotti01]

Is the fan going to be the issue here as at 110kmh there’s plenty of ram air cooling? Maybe the radiator core has an air restriction due to dirt in it? Bugs in the AC condenser maybe? Is the airflow obstructed by additional lights? Was the AC being used?

I was thinking that as yes there would have been high air flow through due to speed. I don't think it could be bugs or dirt on the radiator or ac compressor, as I keep both very clean. It has spotlights but I feel like that should not cause overheating...maybe if I was towing a 3t caravan..
Block radiator or thermostat was my main suspicion.

 

[StarCruiser]

The radiator is easy to check. If any areas are cold after a run then there’s a blockage however Toyota run some pretty good coolant that doesn’t seem to create sludge. Is it manual or automatic? Auto boxes cool through a connection through the base of the radiator. Thermostats usually fail open as they are designed to over cool if they fail. I would be very surprised if it was either causing the increased temperature.

What you’ve described is a reasonable load in reasonable heat and although the thread title is ‘overheating’ you say it has just an elevated temperature on the gauge. If I were you I would remove the spotlights as they will be preventing a large proportion of the ram air cooling from entering the radiator area. I would also check and refil the oil in the fan clutch. Trial the truck after removing the spotlights under the exact same conditions. That will prove one way or the other.

 

[Mazzotti01]

The radiator is easy to check. If any areas are cold after a run then there’s a blockage however Toyota run some pretty good coolant that doesn’t seem to create sludge. Is it manual or automatic? Auto boxes cool through a connection through the base of the radiator. Thermostats usually fail open as they are designed to over cool if they fail. I would be very surprised if it was either causing the increased temperature.

What you’ve described is a reasonable load in reasonable heat and although the thread title is ‘overheating’ you say it has just an elevated temperature on the gauge. If I were you I would remove the spotlights as they will be preventing a large proportion of the ram air cooling from entering the radiator area. I would also check and refil the oil in the fan clutch. Trial the truck after removing the spotlights under the exact same conditions. That will prove one way or the other.

I'll check the radiator for sure. It is an automatic. The fan clutch sounds like the most viable reason, I really find it hard to believe that the spotlights would cause cooling issues. The car wasn't towing anything, and was in the 2400 rpm rev range (ocationally up to 3000 rpm on hills for s short period). The aircon was running but it really should still not move out of operating temperature.

 

[StarCruiser]

The spots are an aftermarket fit and interrupt airflow. Nothing more than that really. If you’ve done exactly the same or heavier loaded trip previously without issue including the loaded roof rack then fair enough you can rule out the spots.

Towing a load that’s streamlined even if heavy isn’t going to place much load apart from rolling resistance once it’s up to speed. Constant stops and starts or hills will be where the load is greatest but with a loaded roof rack the load is constant at a given speed and increases with speed due to the air resistance. It’s surprising what load a loaded rack will place on a vehicle. It could be that there’s been more load on the vehicle than you’ve anticipated. Add in less ram air cooling than the vehicle was designed to have from having two spotlights in front of the grille and a high heat load and the AC on full then you can see the load on the truck is pretty high, not just rotational loading on the engine but heat loading from the AC condenser delivering heated air to the radiator. If it had been a problem the AC would have cut out on its protection stat in the water circuit. Did this happen?

 

[clivehorridge]

I would say that with good airflow, my fan doesn’t kick in. I don’t tow, so I have no experience of your circumstances.
I did find that after replacement of the fan, on steep climbs on hot days in low ratio, as soon as the gauge rose above normal, the fan came in with a vengeance and the gauge returned to normal within seconds.