Ya, this is what I'm thinking and also what someone else mentioned. The truck never over heats, so I don't think it's water-pump or head gaskets, not that the water pump gasket couldn't be leaking a bit. Is there a shure fire way to tell if it's a heater core? also... if it is the heater core... any idea on cost of replacement. I've never done one and have no clue how much work it is to get to it.

 

The problem is you need to pull the entire dash to get at the heater box where the core lives. Just had my core and condenser changed in our 05; about $1,000 and no way I would try it myself. Get your rig up to operating temp, heater on hot, fan on high, if it smells it's almost certainly leaking.

 

Thx, I will do that. The cold morning are right around the corner here in WI. $1000 is pushing it for cash I want to stick into this thing yet. Ugg...