heaters blowing foggy air...help

Your heater core is shot. I'm surprised you haven't seen coolant on the carpet.

krash kendall said:

Your heater core is shot. I'm surprised you haven't seen coolant on the carpet.

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YUP!

Time to replace the heater core.
If you loosen off the radiator cap, that will release the pressure and probably help with the symptoms. This is OK in the winter so long as you keep a close eye on your coolent level (it will evaporate out so you'll have to keep topping it up).

But the only real fix is to replace the heater core.

I highly recommend that you don't put off the repair. Fix it as soon as possible, because that pinhole leak can become a gusher without warning. The antifreeze coating the inside of your dash, carpet and windshield will be difficult to clean.

19mustang65 said:

how much do heater cores cost? easy to replace?

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Cost isn't bad.. I believe the replacement for my 70 cost me $30.

It's a bit of a PITA to replace tho. In a 69/70 you have to remove the dash pad as well as the glovebox. Once those are out of the way it wasn't too bad of a job.

Cut the hoses and buy new hoses for the replacment, it's cheap and makes the install easier (plus you have new hoses).

If it's your 1st time, it'll probably take up most of an afternoon.

if yours is a 65(which I'm guessing it is b/c of your username), pop the hood, look at the rear of the pass. side valve cover. You will see the blower motor sticking thru the firewall and four small tinnerman nuts. Remove the nuts, go inside the car and pull the heater box away from the firewall. Reach around the backside of the box and loosen/remove the clamps holding the hoses to it. You can either remove the box entirely, or leave it in the floorboard, if you leave it in the floor you shouldn't have to remove all the cables and whatnot. There are some little sheetmetal clips that hold the front and rear halves of the box together, pop them off with a screwdriver and open the box. You'll see your leaky heater core and a bunch of leaves and stuff probably. Clean it all up, install the new core, and then reverse removal. Its pretty straightforward, I can do 'em in about 15 minutes now(I'm on my 4th core, ). You might want to lay some plastic in the floor before you remove the box to keep trash and coolant from getting all over your carpet.

Don't forget to drain your rad first. On my '65 I remove the hoses at the engine end after draining the rad. Almost all of the coolant will usually siphon out of the heater core doing it this way. Remove the heater cables and pull the box with the hoses attached out of the car. I find it much easier to deal with the inboard hose clamps this way.

Here are some other parts you may want to install at the same time. I put them in mine a couple of weeks ago and couldn't be happier.

Edit: The website is Canadian Mustang, but the same items should be on American Pony as well. If you go to the homepage a link for American customers should pop-up

Heater plennum

Cowl repair

I don't think the heater boxes are the same, so I would replace with the no-a/c core that you currently have in your car.

I don't have a/c so I can't tell you for certain.