Wide to narrow radiator change on1999 GU Ute

Hi Folks, my GU ute has always given me grief with overheating issues when towing in hilly terrain. I have been through all the easy fixes including several new radiators, new water pump and tigging up minor cavitation corrosion in pump housing, new a/c condenser, replaced foam gasketing between a/c condenser and radiator, installed UFI fan hub/viscous clutch and fan, new genuine thermostat and probably other stuff as well. The vehicle is basically standard except for a 50mm lift in suspension height and a slight increase in boost pressure to just under 15psi as I recall. The engine has factory turbo but no intercooler. Wheels and tyres are standard specification, - 16" rims and BFG 265-75 R16 KO2 all terrain tyres.
Last year coming across the Nullabor on an admittedly warm day of around 37ºC, towing our Track Trailer Topaz van (really a glorified camper trailer, - it just has an internal kitchen and is similar to a Quantum at around 6.0 metres overall length), we were reduced to travelling at about 65Km/hr as the coolant temperature was hovering between 115 and 120º as measured at the thermostat housing. This is on pretty well dead flat country on a sealed bitumen road. We ended up stopping at a small roadside unofficial campsite, until dusk and then set off for Eucla, about 2 hours further on. Once it had cooled down I was able to continue on at around 80 Km/hr, without much trouble, only slowing once or twice briefly if the temp crept up a bit.
I have a brother living on the Sunshine Coast north of Brisbane and it is a nightmare getting to his place from Western Queensland, or getting out again for that matter, due to overheating when travelling the mountainous terrain!
I have been lead to believe that later model GU's had fewer overheating issues than the earlier versions, but there is also the need to change or modify the front crossmember in order to change from wide to narrow but taller radiator. Has anyone else done this mod and if so what improvement if any did you see? Any tips or tricks or any other suggestions to make future outback trips less stressful in the engine cooling area. If I have left out relevant info please advise me and I will try to fill in any blanks, and thanks in advance for your words of wisdom.

I can’t answer your question, but I can confirm that my GU is "basically standard except for a 50mm lift in suspension height and a slight increase in boost pressure to just under 15psi as I recall. The engine has factory turbo Wheels and tyres are standard specification, - 16" rims and BFG 265-75 R16 all terrain tyres". It also has spent the majority of it’s life in my hands towing a Tvan, & with a combined weight of both Patrol & Tvan around the 5 tonne mark.

It is a later intercooled (factory) 4.2. recently sold with 255,00kms. It has been toured in extensively, much of that in tropical Australia & often in high ambient temps. It has a standard factory radiator.

Like you we never drove it hard, but we also never had any overheating problem with it, not once. In Victoria it was common to see (on the redarc temp gauge) between 80 & 90 degrees. In hotter climates 90 to 95, but over 100 if pushing a bit harder up hills, but this always dropped quickly on the downhill side, back to 90 or below. Even in 40+ degree days.

The longest climb recently was driving up to Maleny last June, it was slow but the temperature gauge gave no cause for concern, & I trusted the Redarc gauge.

Now whether this is simple a matter of a different radiator I can’t say, but somehow I doubt it. I often hear folk describing the 4.2’s as ‘kettles’, so clearly you are not alone in your experience, & maybe I just got lucky??

What engine mods do you have? Big pump, injectors, turbo etc etc

Have you had it professionally dyno tuned?

My TD wagon, has everything modified with all the go fast bits. Yes she can run hot, but not as hot as yours. The hottest I've had it was 118c dragging my Offroad Jayco Swan up the big, big hills from Omeo to Dinner Plain on a 40c day. Once on the plain the temps dropped a lot.

I had been through a new triple core Alloy rad, triple core brass, and a Chinese copy on the original radiator, and in the end a Genuine radiator worked the best. I also run the Quikazz Mitsy fan hub and fan, same as the UFI one. The condenser and radiator have all the foam bits stuffed where they are supposed to go, genuine water pump, I removed the High Flow JPC custom pump for testing purposes but never bothered to switch it back as I found the difference was negligible. All shrouds and the air dam are installed.

On beach runs she gets a bit warm, so on our last trip I unlatched the bonnet to let some more air in, the difference that made was very noticeable. I think I might space the back of the bonnet up a bit and see how this goes.

Thank You Cuppa and Mudski for your replies. Cuppa, I think that you may be one of the lucky ones regarding overheating Patrols, certainly not everyone has issues but plenty of us do, in fact when I ordered the fan and clutch kit from UFI, the chap who took my order said that he had a GU Patrol, "99" model like mine and had similar issues since new. He installed the fan and fan clutch kit, which for him solved the problem. I have not been so lucky.
So far I have never had an issue when driving but not towing anything, but even an unladen 6x4 trailer being towed up a gradient so shallow it was impossible to tell that we were in an uphill grade, only the GPS was giving the game away, but a long and very gentle slope would make the temperature rise noticeably, perhaps not to the point where we would have to stop or even back off a bit, but the temperature would rise noticeably.
To answer your questions Mudski, no big pump, injectors or turbo, but we do have a 3" exhaust I had forgotten to mention, everything else is pretty standard with the already mentioned exceptions from my original post. I too have had a 3 core radator, but that had to come out when the UFI fan kit was installed due to space limitations. It would be nice to be able to prove up the concept of this radiator change using a second hand radiator before shelling out $1200 for a factory radiator + all the extra bits like the shrouds etc, but things are not looking too hopeful so far. It has been professionally tuned by Protune in Rockhampton when we had a rebuilt injector pump and new injectors fitted, taking the RWHP from 78 to 120+. That was in 2016, and just under 110,000Km ago.
I might steal your idea of lifting the back of the bonnet up a bit, or even trying lifting the first latch first to see if I get any improvement on my ute first.
Once again, many thanks gentlemen for your input.