Help needed with overheating

[Angla]

I've got a 99 Jackaroo 3.0l turbo diesel.
Running around town and country unladen is fine
When towing 2 tonne boat at 100 Km/hr on a flat road its fine
At 110 Km/hr on a flat it gets very hot and brings on a warning light but takes a while
At 100 Km/hr if you come to a rise it also rises more rapidly now than I have noticed previously.
I have drained and flushed the radiator and then put in heavy duty cycle glycol mix. This seems to have had no effect.
Should I now change the thermostat and then the water pump if that doesn't work OR is that just what a Jackaroo will do?

Angla

[luckyone]

Definately do the thermostat u can test it in boiling water. and use a thermomerter to test the temp and the opening of it. it will be stamped with its temp on it too open

[FNQCairns]

Like Luckyone said but I will say it again- "do the thermostat" just throw the old one away, but test it first for interest next to the new one.
I forget how many of these I have had die on me (they go slowly mostly) last one was only 3 months ago and before I started trusting myself over repair places, what WAS in all probablity faulty thermostats ended up as replacement radiator/s or expensive cleanouts.
The pump will leak and let you know quick smart unless cavitiaton has had a go at the blades but that would be remote possibility.

cheers fnq

[Dex38]

Angla, is the Jackeroo an Auto. If so I beleieve you will find the Auto will be cooled via the radiator. If you do have an auto they do build up a lot of heat whilst towing (more slippage in the torque convertor). Going up hill loads the driveline and you get what you have described. Again if it's an Auto put on a decent transmission cooler in front and if you can , have the auto cooling tank removed from the radiator. This will provide another 1/2 a litre or so of added cooling capacity.
If it's a manual, do as the guys have said in the first instance (go the thermostat).
When you do a radiator flush, don't forget to flush the engine block.
Finally check the radiator cap to ensure its holding pressure. The rubber can get hard and crack but you will normally see water in your overflow bottle. But again if the cap is working on the suction side it will assist in moving the coolant from the overflow to the radiator.

Have fun

Dex

[ShaneJ]

Never ever ever bypass the factory transmission cooler. An extra cooler is for "added" cooling!

[peterr]

Yep,definitely DO NOT disconnect original transmission cooler. Also get someone experienced to check the clutch hub behind the cooling fan as they can lose their efficiency if your mileage is high. Might be an idea to remove the radiator and have it cleaned properly too.
Cheers Pete.

[Angla]

Sounds like all good advice.

Luckyone and FNQ
I have been leaning towards replacing the thermostat but now it is a certainty

Dex38
Transmission is manual and it has a separate oil cooler in front of the radiator.

I have not seen anything leaking around the water pump and I think the cap is not suspect because it does not lose fluid or become low in the reservoir and I certainly havent boiled it yet

Shanej
Doing stupid things is not my style of mechanics

Peterr
I have suspected that but was told the fan really only works on low speeds as windrush does the work at high speeds

Thanks all. will change it saturday and see later as there is no chance to tow the boat with the weather being so fickle

Angla

[Angla]

Just letting people know that I finally bit the bullet and took it to the radiator place on Pickering street Enogerra. Blocked 70% was the diagnosis. Found a new one in Sydney and fitted it the next day. Picked it up at 2.30 pm. Spot on Great service. Courteous too and cheap price $528 for all that.

Angla

[akman1]

A blocked radiator will work fine at low speeds/bush bashing etc but wont at high speeds and loads also a lot of different coolants will not mix together and gum up the radiator unless flushed properly so always try to stick with the same brand of coolant