Help with overheating 4.2td gu dual cab

Hi guys been on the forum for a while but first time starting a thread.

I have a 1999, GU 4.2TD Dual Cab and i am having trouble with it overheating (or at least the temp gauge on the dash climbing) all the time. I live in Canberra so it is probably cold for about 8 months of the year so i dont have to worry about it but nows the time when i start to have some trouble

First things first im a carpenter and i tow about 2 tonnes of trailer to work everyday plus the dual cab has a steel tray with a fairly basic aluminum canopy. went camping on the weekend had 3 bloked and a moderate amount of gear on but not too much and it started to overheat going up the clyde mountain and i was in second doing about 50 stuck behind a horse float, when i got to the top i took the spotties off and had no problems on the way home. a couple of pics below



car modifications to date are to do with engine are

brand New radiator this time last year i removed a pwr triple core aluminum one
winch
tjm bullbar
spotties which i have removed to try to get more air flow
denco water to air intercooler
imatation safari snorkel with standard air box
it has dual batteries under the bonnet
running 265/75/r16 maxxis bighorns
3 inch straight through exhaust
vdo boost and egt gauges
running about 9 pound boost
egt gauge seems to run about 250 degrees normally but when im heading up hills or pushing it itll run up to 550 max

its been fine all winter but now that its starting to climb to the 28-35 degree mark my troubles have begun again. just after some advice/ maybe people that have had the same or similar problems and what they did to fix it?

things i have thought have that might help include,

maybe custom airbox and 3 inch snorkel to get it to breathe better?
changing the denco front mount intercooler to a top mount (maybe a cross country for example)
installing a thermo fan in front of the radiator
new turbo?

could there be a problem with my thermostat?
apart from that im out of ideas as im certianly no mechanic

either get this radiator rodded or replace your thermostat with an OE one.
how is your boost?

Runs about 9 pounds of boost,

Forgive me but what's an OE thermostat?

What condition is your fan in? Also the viscous hub.

Is there much debris in the condenser effecting air flow? Also are all the inner guard rubbers and othe foam strips etc in place around the rad?

How hot are we talking? Do you have an aftermarket gauge or just using the one in the dash?

Also a you can do a quick check with the rad and touch the top and bottom hoses. The bottom hose should be cold if the radiator is working correctly. If it's not then the rad could be partially blocked. If the bottom hose is cold then the problem is likely somewhere else.

Fan seems to be in good condition, my mechanic said the viscous hub was ok

by guard rubbers are you refering to the ones in the wheel arches, if so they have perished and come off (been meaning to replace them)

Foam strips and radiator shroud are in good nick but it needs new rubber mounts for the radiator as they are starting to perish

No aftermarket gauge just dash one, it climbs to about 3/4 but ive never really let it get any higher, I usually back right off or pull over till it cools and by back right off I mean go into second and do like 40 or 50

Yes the ones in the wheel arches.

The factory gauges aren't that great and even though it's at 3/4 it could only be at 90 degrees. An aftermarket one would be a good addition.

Try the hose thing and see how you go before forking out your hard earned.

how old is the thermostat . if it is the original one it may be stuffed , only opening up enough for normal running but when you load it up it may not open any further as required so the engine starts to get hotter . thermostats are usually cheep also , so a good place to start . and as nissannewby says an after market gauge to check temps would be a good idea . just my 2cw .