check that has water flow (thermostat opening), though lot of times they stick full open but not always.
check it’s not smoking out the back pipe a lot, as blocked airfilter can make them run hot.
radiator tubes could also be blocked.
if you took the plastic guard off around the fan this will make them run hot, especially hot weather as fan doesn’t pull air through radiator properly, instead pulls it from sides, which tends to disincline the thermo clutch from doing what it’s meant to do.
if it might be radiator tubes you put a fire unit on the outlet end and backflush it.
could drop the impeller off the water pump, but doubt that’d be it.
i gather it’s not blowing any coolant out the radiator cap vent with normal operation, as this’d suggest head gasket or cracked head or rust holes in head or cylinder liners. Generally any tripping the radiator cap pressure valve and release of excessive coolant suggests something bad, and you can idle it and look for bubbles with cap off is gives an idea of that sort of thing too.
I suppose if your injection timing is way out, but doubt it. it’d likely idle wrong and stuff
might wanna backflush the entire block and radiator (though thermostat might stop you flushing the block), don’t overdo it if using the firetruck
oh check it still has the fin things on the tubes of the radiator too, though generally you can lose a fair bit of them from corrosion etc and not too bad, my nissan had lost about 1/3 them still was running cool.
