98' F-150 won't defrost and coolant smell???

This is my dad's truck and he told me about this odor last week...last night after I did a brake job I took it for a test drive. It was cold outside so I let the truck warm up w/ the heater on. I got in and noticed the windows fogged up so I turned on the defrost, after about 15 min. the windows were still fogged up! There was also a warm coolant smell coming from the vents??? Also, no matter what position the temp control switch is in (cold or hot) everything comes out hot!
I felt both radiator hoses and the upper was warm and the lower cool to the touch??? The coolant overflow reservoir was also not very hot or pressurized for that matter!
I was leaning toward Heater Core or Thermostat. Any help would be appreciated!

 

I would replace the thermostat first along with a good coolant flush.

Heater core is a HUGE PAIN IN THE you know what to replace though it does sound more like a core issue.

 

It definitely sounds like a leaky heater core. Don't ignore this condition nor put off the repair, because inhaling coolant can damage your kidneys.

Check the heater core connections at the firewall. If you're lucky, it may be a leaky connection that dribbles into the heater box.

 

I had a 1998 F150 with the same problem. It was a leaking heater core. Feel the carpet below the center of the dash for dampness -- mine was damp.

I replaced my heater core myself, but it was a major job. I found a procedure for doing it online at the time, but even then it was difficult because of my lack of familarity with the terms used in the procedure, and the poor illustrations. If you decide to do it yourself, I stongly recommend that you use your digital camera to record every single thing you disconnect before you disconnect them. I spent a lot of time putting it back together because I couldn't remember exactly where everything went.

 

Go to the local auto parts Autozone/Advance or whatever and get a tube of AlumAseal($2.00) dump it in the radiator and the leak goes away and when the weather warms up replace the heater core. The AlumAseal will get you thru the winter. Have a nice day. Geo

 

do not put stop leak junk in it you will run in to pros later with water flo in ur engine block replace heater core

 

Thanks guys! I will have a good opportunity to "further investigate" the problem during this weekend. He still says it's doing the same stuff...I'm just puzzled as to why the A/C won't get cold, not that he needs it this time of year...I will get back with to ya'

 

The A/C needs a fully working coolant system to work. If you have a clogged core or leaking coolant system, the A/C will not work.

 

Ok, the problem was the heater core and the blend door and blend door motor. He had this repaired at a shop for a little under a grand! that's about three hundred more than the quote. Labor is Not cheap! Thanks for all the leads/advice!