I have just bought this truck---96' 2500 diesel---- It had no heat when i bought it so i put a thermostat in it and it has not gotten any better just luke warm. i have checked everything, belt routing, swithces, cables, coolant level. i have gotten no where. Someone told me that i have a air lock which is probably correct because i hear a bubbling noise comming from the heater core. i can not seem to get it out. I tried letting it cool completely down several times and even let it warm up with the rad. cap off. someone also told me about some air bleeder check valve that i do not know where it is located or weather it is working. Any help would be great because it is 10 deg. here.


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Diesels take a LONG time to heat up in the winter. And in 10 degree weather, it's almost a foregone conclusion that heat will never be achieved, at idle anyway....lol. I have a pizza box in front of my radiator, only. In ten degree weather, I make pretty good heat. But uncover the radiator, and I need near highway speeds to warm up the engine.

Your thermostat mounts sideways. On the thermostat itself, there is a little tab that is loose, but secure in the flange of the stat itself. That's the bleeder. This bleeder must be in the top (12 o'clock) position. If not, an eternal air pocket can occur.

And another huge thing you can do is just before installing the thermostat, fill the block up with as much coolant as it will hold. Don't forget, it will seek it's level in the radiator as well thru the lower hose. Keep the radiator capoff and you will not get coolant splashing back as air is trying to escape.I'd wear goggles if it's your first time.

I would yank at least one hose to the heater core (pull it at the engine side) and run the hose waterthru it to confirm the heater core itself is not blocked. Reattach with a new clamp too. If it looks rusty, mine as well open the rad drain and flush the whole system.

I think you do have air trapped. LOTS of air....lol.


I hope this helps.

Good luck with your ride.

 

I do agree, it does sound like an air lock, my only guess would be to remove the under the hood hoses from the engine and use your garden hose and push water through it that way.

 

Make sure the heater hoses aren't swapped. The heater core should be filled from the bottom hose and exit out the top. You can also install a bleeder in the hose from the heater core.