Wierd over heating issue

[HSVMONARO]

Recently i acquired a 98 Ln167 with the 5l motor in it, the engine has only done 220,000 clicks and it has installed one of those wierd Hi-CLONE 2 things in it, anyway when i drive it and put something on the tray or tow a trailer behind it and sit on a 110 the temp guage rapidly rises to the red, however if i drop back to 95 or even a 100 the temp goes back down?

I am confused as to what would be causing this issues, a week ago i dumped the water/coolant out and topped it back up with decent coolant but this hasnt seemed to help. Any advice would be muchly appreciated thank you.

[hylux]

My guess you need a new fan viscous clutch. But check the radiator hasn't clogged with mud first

[dave g]

make shore the thermostat is in it. it is there to slow the water to give it time to cool in the radiator and close off to heat the motor when cold.

[cmilton54]

The other cause, maybe it needs a new radiator, it may have corroded a bit and not doing a full heat transfer under higher load.

[benc_wa]

There are heaps of possibilities - the above included. To check the oil viscous fan clutch when it does get hot pull over and 1 check fan is working, then turn car off and try and turn fan with ur hand. If it is stiff to turn then oil isnt your problem. If it is loose then it probably is.

These engines are known to get air pockets in the cooling system which doesn't help much. U can try and clear them by running your car on idle for 45m to an hr with the radiator cap off, the heater on full set to fresh (not recycled air). You will see bubbles come to the surface periodically if it did have a block, but u dont have to stand there watching! Then, after about an hr, switch off and let it cool down. Right down. like 3 hours or so. Then top up radiator and overflow to required mark.

Hopefully this will help. There can be air blocks behind the heater set up though which require pressurised flushes to clear - see a mechanic for that one they will have a fitting for the radiator top.

The other problem can often be airflow through the radiator, especially with the air con condensor sitting right in front of it. If you have a Bullbar check there is enough air flow, may have to move your number plate etc even drill some holes...and u can install after market thermo fans in front of the air con condenser blowing back through both of them.

[Gipsy]

My guess is the fan isn't the problem as it only overheating at speed over 100k, the airflow at that speed should be sufficient, fan only useful at lower speeds. Check thermostat and radiator core, if you changed out the coolant the problem is elsewhere.
To burp the system put the lux on an uphill incline and check for bubbles. Thermostat may not open fully. Also if you ever replace the coolant in future use a rescaled/flush before you replace the coolant.