1989 takes 10 miles to get a little heat 1998 takes 20 miles both have winter fronts and cummins thermosat How do you get them to run warmer other than pulling one of them on the trailer to make the engine work.Still did not find leak at injecion pump on 89 at idle any ideas .:cool2:

Do you have a block heater?
At one time you could buy a heater that was wired into the battery and placed on the floor to keep the feet warm.

I'm not sure what to tell you on that one. I know when it gets really cold outside I have to plug up the truck, which helps. I know that pluggin it up, also deals with the glo plugs. Have you changed the thermostat? What about the water pump? Just thoughts. I know I've had probs like this before out of different vehicles. I'm still new to the mechanic world, just ideas.

On cold mornings I plugged my truck into a timer and had it start a couple of hours before I got in it to start. Didn't do anything. So I tried plugging in all night and got heat in about 3 miles, much better. I'll bet the heater is a low wattage affair and needs awhile to heat the engine. Try that if you haven't already.

It could be that the newer one is innercooled and the older one is not.

Best thing is to plug the truck in right after you shut it down. It's already at temp so the heater hardly works to keep it warm. At least that is what I do. I also have the cold front on the truck. Takes about 5 miles or so to get heat running 45-50 mph.
If you are not getting heat in the cab you might start checking your hoses. If they are old they could collapse or have an obstruction. That would make it difficult to circulate heat. The next thing would be to check the function of all the equipment behind the dash. Switches...dampers...vacuum lines. Make sure everything looks/ operates. I know on the old Chevy's and Ford's that the control panels for the heat would go bad. The fan would work, but the heat adjustment would not. Just went to the junk yard to get a replacement.

You can also get seat heaters from Geno's garage. I don't have them but sounds like a good idea.

Cummins600, good idea about plugging in the truck when it's hot. I tried the last two nights with temps 12-16 degrees. Works better than plugging in the cold truck at bedtime. Heat in three miles.

did all those things new thermostats ,cummins, new hoses winter front but all you guys live in the tropics ,its cold in Canada I will have to park them for the winter and drive vw heat in 1/2 mlie water pump ,hows that going to help when never overheats in summer

Just a thought, but could your heater core have issues. Not much more I can input after the previous replies.
Mark

Yeah I don't notice the noise when you plug it in and the element warms up.

I can't argue that we are in the tropics in comparison to the climate in Canada this time of year. Sounds like you have tried about everything there is. The last comment would be the heater core, but that one is taken. I don't know from here, these ideas always worked for me