[Richard and Rhonda]

Kim,

Great advice from Michael and Wally. In addition to that, you will need to do two other things. Make sure the heater control valve into the heater core, the one controlled by the panel on the dash is wide open. Confirm that it is by finding it at the heater core.

And here is the kicker. With a diesel you WILL NOT generate enough heat at idle to really get the thermostat to stay open and provide any kind of coolant flow. Get it out on the road and drive it. I know it will come up to about operating temps according to the guage, but you are not pumping much water around at idle.

If all of the suggestions about making sure all valves are open, and the engine is circulating coolant, then you can do it the messy way. Find the hose connections in and out of your heater core, loosen them and loosen the hose until you get coolant running out.

Keep us posted on the results.