I have had a number of helpful replies to my truck not heating properly in the cab. I talked to a mechanic and he said he could " blow out " the core. There is some residual water that I can hear moving but it does not leak or stink. Does anyone know the procedure for blowing these out ? Any advice would be helpful.
2001 Dodge 2500 5.9 diesel 4 x 4

 

garden hose both ways DO NOT USE AIR

 

How can I get that little bit of water out that is sloshing around ?

 

I second the garden hose but watch your pressure. I never just cranked open the valve at first until I got it flowing good. Also reverse the flow or both ways til it runs clear. As far as water sloshing in the box just a small drill bit and when the water is out put a dab of black silicone over it. If you have water in your box it sounds like your drain hose out of the firewall might be plugged. You can use a coat hanger to try and clean it out. I've done some and I'd swear you would get a gallon or more of water out of those things!

 

The heater cores in these trucks have the inlet and outputs at the top of the core itself. Any gunk that does settle in the core goes right to the bottom for the most part.

It's a very poor, non self cleaning design and only gets worse as time goes on. Flushing the core out might help a little but all your doing is flushing out the remaining part of the core that is not gummed up. That's why the heat output gets less and less.

The core on my truck is so plugged, it does not give out any heat, the water doesn't even circulate through it. The new core is sitting on the bench waiting to go in as I type this. Guess what I'm doing for Christmas?

Jeff

 

Thanks for the replies. I have heard that the core replacement is a tough job.