hey guys,
my truck does the same thing.... it can sit all day on high idle and the cab is not even warm, makes it hard to jump in and warm up while your working outside in the bush at -40

 

Diesels use very little fuel idling and therefore generate very little heat. As well it is very hard on these engines to idle. Soot and unburnt fuel build up in the EGR cooler and valves. It is a bad idea to warm these engines up idling for more than a minute.

 

I was having the same problem with my Job 1 450, temp gauge stayed cold and heat was only from supplemental heater. It went on for a couple of days and then the CEL came on. I took it in and the thermostat was bad.

 

It would seem to me that if the truck is running and the temp gauge lowers that much, i.e. from halfway to cold, the thermostat must not be working well. Seems if the engine is running, not idling mind you, the thermostat should get this thing up to 205. Diesels cool down idling, and letting one sit there for 20 minutes or even 5 is too long. Cold cylinders wash the rings with fuel, which ultimately dilutes into the oil. Therefore the change in oils in these new ULSD fueled trucks. If youre worried about the truck being too cold with the oil being thick, use 5w-40 synthetic, and plug in that block heater. I use mine alot. Its better to get in the truck, sit for a minute, then take off and let it warm up while working it than to let it sit and idle. Diesels dont stay warm idling, they actually cool down. Just my 2 cents.

 

i know idling a diesel is not good.... unfortunately i work the truck in northern canada and plugging any vehicle in at night is out of the question.... and if your working in these kind of arctic conditions all day you need something warm to get into.
if we turned the truck off when you get to your work site it wouldnt start in 2 hours at -45C
so good or bad, thats the way we roll up here, its just too bad that ford cant come up with something to make it run a little warmer