Ok, I did a search and found that the heaters seem to be a common problem on this truck 2002 4.7L.

Weathergot cold for the first time, so I turned the heat on the truck and got cold air.

Passenger side is also blowing cold air.
When I'm at higher rpm going down the road it still blows cold air.
I have always had the "sloshing" sound of water in the cab, since I've owned it (about 7 months) but the coolant level has never gone down, and I've never had water come through the vents or leaks or anything.
The coolant level is full.

I'm wondering if the previous owner bypassed the core somehow. But I don't see anything obvious. The two hoses that I believe go to the heater core are coming from the water pump, straight into the firewall.

I'm heading up north for Xmas, and it looks like its going to be a chilly drive. Unfortunately I don't have time to take on the hellacious job of replacing the heater core. From reading previous threads it sounds like a pain in the butt.

Any ideas of what it could be?

 

Suggest you get a big woman to keep you warm.......

Just joking dude, haven't heard much about this problem..maybe someone else will chime in with a fix.

 

It sounds like the notorious GM problem where the crappy antifreeze they use (DEXCOOL) stops up the heater core. That is why it sounds like water running. I had the same problem with a '99 Blazer. I had to flush the radiator system and put green (regular) antifreeze in. You might try this yourself as a possible fix or take it to any garage or oil change place if you don't have the time before xmas. Of course I am only speculating here........I haven't had my Dodge long enough to here all of the horror stories. It just sounds like the same problem.

 

Well your pretty much right Kebo.

I played with it a little more. Figured out it would blow hot air for about 5 seconds right when you went from cold to hot on the dial.
then it would cool off quickly. If I put it back on cold, and let it sit for a while, I could get 5 seconds of heat againwhen I switched it again. (figured the flaps/doors on the heater core had to be working for it to blow hot for a second so it must be flow like Kebo mentioned)

I took the hoses off the waterpump and tried to blow through them. The first hose I couldnt get any air through.
The second hose (the one that T's off into the resevior) I blew a little bit of air into it (plugging the other end of the T) and some debris came out the other hose.
Put the Garden hose on there, and ran it through both ways a few times. Got more debris out of it.
It wasn't metal. Just fairly softrust colored crumbly pieces.

Anyhow, flushed it through both ways and put it back togather and the heater blows nice and hot now.
Took about20 minutes.

Thanks for the tip Kebo.

Now I'm waiting for the heater core to eventually break so I have to pull the whole dash out to go after it.

Happy holidays
Ken

 

What you might try after you get back from your holiday travels it to go to any autoparts store, I use Advanced, and get some Prestone Radiator Flush. Flush the system with it and refill with with antifreeze. That should take care of any "junk" you couldn't get out by just flushing with water.