Hi guys,
so I've had this issue for about a year, and I'm not quite sure, but I suspect a bad heater core. First off, the heat barely works. My 7.3 heats up faster in cold weather than this. Also it has a very slow coolant leak, and I can smell it. It's pretty old coolant, and will be getting replaced soon, just as soon as I can figure it out. Doesn't seem to matter if the heat is on or not, I can smell coolant, but it is a stronger odor when the heat/blower is on. Last year I opened up the box the heater core sits in and it looked bone dry, I will be opening it up again to inspect soon. Another weird thing is the windshield doesn't instantly fog up, like it was a bad heater core, it just won't defrost because of the heat not working. Any ideas? Any help would be much appreciated!

 

I'd try backflushing it and see what comes out. Feel around the passenger floor carpet and see if anything is wet.

 

Ok, I'll give that a try and see what happens.

 

At least it is easy to change on that year compared to others.

 

Based on your symptoms, I would also guess that a bad thermostat might be the cause.

 

 

Mine was bad in my '02 and didn't wet the carpet or the inside of the housing. I could smell it and my windshield wouldn't steam over but would increasingly fog the longer the drive. When I pulled it there was a small drip about an inch up off the bottom and an inch inward from the inboard edge. Easy change out after a quick class at YTU (YouTube Univ). Wouldn't ya know it..... two weeks later the radiator failed. Now new t stat, rad, hoses, recovery tank i a twice flushed system. Now the water pump's starting to chirp...I think. Going to WD-40 the idler and tensioner pulleys this evening just to be sure.....