Title says it all, started last night. There are no visible leaks anywhere under the hood, my best guess is the heater core as the windows also want to fog up. Any other possible causes? Has anyone replaced one yet,trying to decide if I want to tackle it after finding out the dealer pay 6.5 hrs. to do it. Thanks in advance for any info. Brian

Sounds like the same exact thing that happened in another truck I had. Yes it was the heater core. It was not fun.

Good luck

That's what it is. Had mine done awhile back by the stealer, 800 and some change.
They told me they had to take the dash out cause the only way it comes out is through the top.

If you are not planning to keep the vehicle for an eternity, ie, trading soon there is some stuff at auto supply places that you can put in the cooling system that plugs up small leaks. Might be worth a try. Probably under $5.00. If you're going to hang on to the vehicle for long term, then biting the bullet (like that on a 16 inch Navy gun) is the best bet. Good Luck.

you could always pour some pepper into your cooling system. it works real well and it is a cheap try. we use it all the time for leaks on logging equipment.