Guys I am new to diesels but here is my question.. On my truck here lately it has been 30 degrees,, I am driving only 11 miles to work. This is the temp my truck is runnng now in the cold.
Driving out on the open road after driving for 8 miles at 65 mph the tempature is just barely touching the 2 on the 200 mark and I beleive this is ok but what gets me is after the 8 miles I am letting off and coasting to a stop sign and then just ease off and the next 1 mile the speed limit is 45 so I have to go slow and the tempature drops at least 1/8 inch back to the cold side,, go figure. It would seem that the thermostat should be closed since it hasn't reached 200 yet and if it was closed even with slow spped driving the temp should slowly ease up some.. If I do drive it say 20 miles the temp will go to the straight up mark and act as if it is opening and closeing the thermostat but on these short trips it isn't working like I think it should.
Kinda scares me due to not getting the engine up to full operating temp before shutting it down,,

 

Get yourself a winter front from DC. They are $100 and worth the money. This will take care of your problem

 

off my radiator to see if it would help. I have a piece of thin famica material that goes on your countertops. I cut it to fit just in front of the radiator leaving only the bottom 2 of the radiator exposed. Results was the truck warms up exactly the same as before it was blocked off.

I guess what I am wanting to know if mine is operating the same as your trucks are. My typical trip is I leave my house and drive at 35 to 40 for 2 miles then hit a 4 lane and drive for 8 miles at 65 mph,, after these 8 miles my tempature gauge is barely touching the 2 on the 200 sign. then I drive for 1 mile at 35 mph the temp gauge will drop about 1/8 inch to the left showing the engine is cooling down even before the thermostat opens.. Now after about 15 miles the temp will hit the straight up 200 mark and seems to open and close just fine,,, is this how your works,, if so why does it cool down even when the therostat is suppose to be closed..

 

Ive noticed mine doing the same, actually getting cooler when not pushing the engine too hard. The temps were below zero here today.

 

Mine does the samething, 12.5 mile downhill trip to work doesn't warm up completely. Warms up fine coming home, all uphill. These engines need to be worked to heat up.

 

All seems normal according to what you are saying. Do you hear the fan kicking in, you know the slight roar of what might sound like a jet engine If you do then everything is fine. My fan will partially kick in even when it's 40 outside if the Turbo needs it or even if I run the Defrost.

 

If you are going to buy a thermostat go to a Cummins dealer, thay are $16. $40 at the dealer and $30 at the parts store.

 

Remember, there are no throttle plates in these engines, therfore they get a full atmospheric pressure charge of cold air on each intake stoke plus anything the turbo is dishing out. If you don't work the motor hard the fuel input to the engine is low, thus not a lot of heat generated when engine is not working hard. Since diesels can burn mixtures as lean as 60:1 (air:fuel) when not working them they tend to cool down from normal operating temperature when ambient conditions are cold.

Even if the thermostat is closed they can cool off a bit when its cold out.

 

Thanks for all the information,,, I no when I had cut a piece of famica,, 26 x 30 and it almost fully covered the radiator, the tempature did exactly as before the radiator was blocked so I knew that covering it would not make it heat up any faster.
]
Thanks again