i just changed out the thermostat and double checked that i have no air in the system. the radiator is full and the heater core lines are about the same temp. the truck also takes FOREVER to warm up even with the block heater plugged in. the strange thing is that when i started it up after filling the radiator up to help bleed the system it was blowing hot air, but when i started driving the best i can get is luke warm. i need help ASAP please. i live in ND and it's starting to get pretty **** cold. 2003 RAM 2500 stock.

 

You said that you made sure there is no air in the system. It sounds like you have air trapped in the system.

Did you fill the system with the thermostat out? If no, then remove the plug that is in the top of the head next to the thermostat. Fill the radiator until coolant comes out of the hole. Put the plug back in and finish filling the radiator.

 

i pulled out the temp sensor next to the thermostat and there is fluid there. i'm thinking that the air might be stuck in the actual heater core. gonna let it sit over night and try again in the morning. i plan to try to bleed the core out and maybe i'll get lucky with it.

 

btw i filled it up with the thermostat in. but nothing really explains why i had heat at first then nothing when i started to drive. really hoping that the core just needs to be bled out.

 

what temp do you get to?
also would not be the first time a thermo was bad out of the box, Highly recommended you instal a cummins stat, vs aftermarket just to help keep the chances of getting a faulty one to a minimum.

 

the truck is getting up to about 170 F on the gauge, but it's hard to get the darn thing hot enough to open up when it's below freezing outside. i got it hot enough to open up yesterday driving down the highway. gonna check here in a few minutes and i hope that some more air has bled out on it's own.

 

ok, i've check everything i can think to check, and no air. gonna run down the highway to town and back (about 30-40 miles round trip) and see if i can get heat. fingers crossed.

 

You can check the thermostat by placing it in a pan of water on the stove and use a cooking thermometer to see at what temp it will open.

I start getting heat with the engine temps below 140*

 

the thermostat is not the problem. i had heat yesterday when i re-filled the system and was idling around 160-170 F. i went to drive and the air went to luke warm. idling now the heat is luke warm with the temp around 160-170 like yesterday. i drove it down the highway today and the temps are about normal hanging around 190-200, but still no heat. what else can i do to make sure there is no air in the system?

 

also the radiator is warm/hot on the driver side and cool/cold on the passenger side. what could cause that?

 

The air may be combining with outside air for less heating or there could be an obstruction not allowing the coolant to flow through the heater. You might connect a water hose to the heater line and the other end open and see if there is good flow through the heater.

But since your radiator is cool and hot it still sounds like your system still has air in it. There is a chance that your water pump may have lost some of the fins but then the engine would get hotter.

Put some cardboard in front of the radiator which will help to warm it up.

Try again and take the plug out of the head next to the thermostat. It is easy and will make sure there is no trapped air.

 

There is a chance the heater core is plugged and not transferring any heat. This can be the case with both to/from lines being hot.

 

You have been given good advice from papaduck. As AH64ID mentioned, it is possible the heater core is plugged in this case.

 

Broken blend door maybe?

 

blend doors aren't the problem i fixed those in september. i'm gonna drain the system and check the core flow and refill again slowly. like i said earlier it had heat when i first filled it back up, but went to luke warm and stayed there since when i drove it