The Detroit Diesel 2-71 in my Son-in-law's HD5G trackloader doesn't appear to have a thermostat ; I suspected this, but since I installed a new temperature gauge and SIL worked it hard enough that it should have been thoroughly warmed up, the gauge barely moves off the peg. It is nice to know that the cooling system isn't plugged up, but now we would like to get it to warm up properly.

What temperature rating would be best for this machine? We plan to do some digging and loading pit-run gravel as weather permits through the winter; the actual process will be to warm up the machine, load two small dump trucks, shut down and haul the gravel ~1/4 mile away, spread the gravel with another machine, come back, re-start the loader, repeat, etc.

Are there any "Gotcha's" that I should be aware of  before opening the system?

Thanks in advance