I have a '99 Expy with the 4.6l. Last winter, there was a hint of coolant smell when the heater was first turned off. Drove it all summer, never smelled it with the AC (though I don't use the AC much). Now that the weather is getting cooler here in Ohio, the coolant smell has started again, only this time stronger. I only smell it when the heater is running. It can also be smelled in the engine compartment.

After reading about the amount of work it takes to replace a heater core, I took it to a local shop. They had it on the pressure tester for 10 minutes with no drop in pressure.

A few years ago it had the problem of the heater hose connection leaking on #4, but that caused misfire problems and did not create a coolant smell in the cabin.

Suggestions on what to look for or how to find the leak?

 

I've seen water pumps leak at the shaft but only when the engine was running. If the shop pressure tested it with the engine off, this could be why there was no noticeable leak. IMO, if you're smelling AF, there has to be a leak somewhere, somehow, sometime.

 

Even after mine was filling the cab with overpowering odors & coating the inside of the glass with antifreeze fog (and killing a few brain cells....Wheeeeee), there was only an occasional drip of antifreeze from the A/C condensate drain. I replaced mine 3 days ago. Took me 16 hours by myself but was taking my time bagging screws in groups & rereading & rewatching video as I progressed (I have CRS). Mine was a very slow leak that was hard to detect too. I suggest you replace the core asap or you'll have a stinky truck and sticky foggy windows. You're at the right forum for help changing your heater core. With the help of reading all the posts here I did it, other than that horrible rattle by my glove box that must be from the one screw I had left over. My two bits of advice is don't pull the dash all the way out & when you get to the core, cut the pipes on the core so you can just pull them out from under the firewall, and only use distilled water with antifreeze. When reconnecting lines with new o-rings wet them with antifreeze & they will snap on easily. Watch the youtube video & print out the instructions you can find on FTE. Go to ford & get the o-rings & clips for the lines & shop local auto parts for the core. Got mine at advance auto with the $10 coupon from fatwallet.com for $43-$10=$33.00 And the o-ring kit @ ford costs $31.00 (crooks). One more thing!!! Get a case of beer to lure a mechanically inclined buddy to help with this little project.
Or budget permitting just fork over a grand & drink all the beer on the couch watching a ball game. Today I get to replace my alternator 3 days after the heater nightmare. And fix my rattle before I go postal listening to it.

 

I don't think the pump seal would put any smell in the cab. IMHO

 

I beg to differ. Any AF leak is potent enough to be drawn into the fresh air intake when the blower is on. It is more noticeable in the winter because the windows are usually up.

Also, he said, "It can also be smelled in the engine compartment." That being the case, a leaking heater core doesn't produce an odor in the engine compartment because the direction of the air flow is into the cabin.

 

And likewise, the core leaking & dripping from the condensate could be "smelled" outside the truck. Don't know how hard the water pump is to replace, but hope he doesn't have a leaking core. My kuckes are still a bloody mess from pulling that dash.

 

"that horrible rattle by my glove box that must be from the one screw I had left over"

Why are you arguing with me when you admit you have a screw loose somewhere. LOL

 

Of course I do, but like my favorite writer with sand between his toes said, "If we weren't all crazy, we'd go insane"

BTW, wow what an easy alternator to replace. Almost makes up for the heater core R&R from hell(16 hrs and a pint of blood).

Hey pdqtimetrialer, you find the info you needed?