Outer Limits 4x4 Board

I recently got a new ute. Patrol 4.2 turbo
I suspect that the thermostat has either been butchered or removed as it takes ages to warm up and runs really cool, ie just above the cold unless it gets worked hard.
My last one of these was a battle to keep it from cooking.

Is there any reason that diesels need to run warmer?

try replacing the temp sender and thermostat and see what happens pretty sure you'd get change out of a fifty.. IMO running too cool could cause un-nessicary wear to the motor..

Wot he sed.

wait till it overheats!
topic on its own!
just leave it!

Cold running on any engine is not good. The designers put special devices (thermostat) there for a good reason. One is that you get a lot of condensate running past the rings into the sump. This contaminates the oil and is acidic - wear and tear on the bearings and cylinders. The quicker you egt the thing to operating temperature the better. Another reason is emissions. And of course there is the safety - your demister works much better when the engine is warm, and you feel more comfortable.

I suggest that you replace the thermostat

a new gasket is cheap .. pop the thermostat housing and see if there is anything in there ...

I would be making sure that the temp reading you are getting is actually correct in the first place. Your sender or gauge could be wrong

Get a hold of a decent electronic thermometer.

So I have been running this thing around for a while now. No real issues day to day and it probably runs around the 1/4 or less till it gets worked or drops down to virtually nuthing down hills.
Problem was in the bush with camper trailer, real steep hills, low range 1st, high rpm therefor high water speed, and it jumped up to nearly boiling
Pulled the housing and it did have a thermostat abit strange tho. Intact.
Partially open at cool, probably 4mm.
Got a new one that looks a fair bit different so will see how it goes.

my TD42 did this too. Thermostat was old, didn't really close. Oddly though, it was an adjustable thermostat and someone had set it so it would always be open.

Replaced it with a genuine nissan thermostat but it ran too cold (strange!) so that was modified also to open once it was a bit hotter. It worked well.

Do NOT run your TD42 without a thermostat, you risk overheating it and you won't know until it is too late.

People who take thermostats out are morons too lazy to fix the problem properly, run an engine constantly cold will do it more harm then good. Flush the cooling system, new Nissan thermostat and gasket, new good quality coolant and maybe a new radiator cap.