Willem replied:

What are you doing cruising above 110kmh?...lol

I had similar problems and eventually the radiator sprung a weep. The radiator bloke advised that it was repairable but that the water vanes were getting tired and a new radiator was a better option. So I replaced the radiator for $495 and fitted it myself. The radiator was the original one and had done 320,000km. Now the GQ runs cool, even on hot days.

Cheers

Exploder replied:

I would say probably a Blocked radiator core.

donks1 replied:

when at operating temp, touch the top of rad and then bottom

if the top is hot and bottom cooler, obvious rad problem
is it auto or manual.. auto running hot will cause similar problems, and then you have a whole new list of thing to look at...

good luck.....donks

J.T. replied:

On my GU Patrol 4.2 td had same problems.Took radiator out and the fins were chockers with sand,locusts,bugs and two birds.Took it into a radiator mob anyway and got it roded thru the core.It ended up being only the external fins full of crap that caused it.Now its all good.

nowimnumberone replied:

how is the fan clutch?
check it by turning and you should feel a fair bit of resistance.
ps do it with the motor not running lol
cheers

Member - andrew B (Kununurra) replied:

Gday Stefan

I had similar problems with my GU 2.8......turned out the radiator cores were about 2/3 blocked, so much so it couldn't be rodded so had to get a new core. I also got a new thermostat as the old one didn't fully open - make sure you test it properly, as once they have got hot they can warp a bit and only open about half way restricting flow. that was about 2 years ago, and the other day was the first time it got a little warmer than the norm, but I was doing 130 passing a Road train on a 45 degree day with the aircon on, and as you have experienced it recovers quickly once you slow down.

I would recommend you fit a low coolant alarm...and also check that the small radiator hoses were replaced as well (there is a couple down near the oil filter and near the overflow bottle. I lost the one near the oil filter and It dumped all of the coolant under the car, $6500 later I was on the road again. They are a PITA to get at, but I have a close eye on mine now

Cheers Andrew

62woollybugger replied:

Its a common problem with the GU 2.8. Mine did the same at around the 100k mark. The radiator has a large number of small tubes, which block up, mine was 60% blocked. My mechanic took it out, removed the top & bottom tanks & cleaned the tubes, now the temp gauge doesn't even get to 1/2, no matter how hard I push it. The mechanic knew what the problem was when I told him, he didn't even have to look at it, as he has seen quite a few with the same problem.