Engine temps. How hot is too hot?

Hi. I have the 3L1KZ-TE diesel in my auto trans equiped, 96 Custom with a 76 degree c thermastat and have done a good number of mods to keep engine temps down. Cooling system has been throughly checked and I have an after market temp gauge in degrees C. On the flat at 100kph it sits at about 85, up long hills gets up to 100d, long hills with a 1100kg boat gets it up to 110d. Any info on what yours does would be a great reference. Tests were done in about 20d ambient temp. Rich.

Yeah it's not as hot as mine... mine sits around 90-95 degrees around town everyday driving and going up a long hill it tops 110 I stop before it goes any higher 105 now. This is measured with an engine watch dog themocoupled to the head of the engine. The standard gauge goes up past half way once temperature reaches 95 degrees.

I have had this issue for nearly 2 years now and it's slowly got worse over that time. I replaced my thermostat with a 71 degree one in hope it would open earlier and wider to allow more cooling but it hasn't.
I have flushed the system so many time now and bleed the air out every time and it still overheats.
My viscous fan cuts in at about 83 degrees and seems to be roaring loud enough. The only thing left for me is to replace my radiators and water pump and see how it goes.

I strongly suspect you have a radiator blockage issue. Blockage is almost always the cause of overheating and no amount of flushing will help. They have to be removed , at least one tank taken off (idealy both which allows visual inspection) and 'rodded' to remove build up. The top radiator has to come out through the top and the bottom one is tricky as you have to support the A/C radiator while you un-do the support frame for both. You might think the flow looks good when running the hose through the system at the moment but this gives no real indication. Start by taking the top one out and have this checked. You will then know if it's worth doing the bottom raditor if you find scale build-up. Let me know if you need more info on this. Cheers. Rich.