coolant leak under glove box....

Sorry to say, but it is not a one time thing. It's most likely you have a leak in the heater core. If memory of my '67 serves, the hoses go through the firewall before mating up with the connections on the heater core, so I guess it is possible that you have a leak in the hose or at the junction. But I believe you are still stuck with removing the box to investigate.

I recall it being a Saturday morning project, but that was 12 years ago.

Yeah you definately have a heater core leak. It will probably only get worse. Its actually not that hard of a project and is a cheap part.

Heater Core

black_demon said:

so i was working on the stang today, and when i was done i sat inside and enjoyed the rumble of my exhaust... as i rev it up i notice a greenish fluid on my passenger side floor mat and watch drips of it coming from the heater box under the glove box... i watch if for a few more seconds and it stops... a few minutes pass and nothing more.

Can i pass this off as a one time thing or do i have a more serious problem on my hands???

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On my '67, the hoses go through the firewall and connect to the heater core inside the cockpit of the car. You didn't say what year your car is, but if it's in this forum, it's probably about the same vintage.

Depending on when you last replaced your heater hoses, you could be lucky and just have a worn out hose or loose hose clamp. Look up there with a flashlight while it is running and you should easily be able to tell. If the leak is coming from the fiberglass box, it's the heater core. If it's coming from the hose connection, you'll just have to replace the hose.

Good luck!

yah, its the heater core, but it just might be the hoses. You should try to fix it asap; cause that fluid doesn't drain anywhere, after it comes in, it soaks in the into the carpet and maybe stands till under the carpet onto the floor pan.

Edit:
It's not hard to take out, its a little more challenging to put it back in though. (assuming it is a vintage) I had to have my brother help me. MustangsMonthly has a great article on it.

If you do get the box down to look at the hoses, go ahead and replace the heater core anyways. They are fairly inexpensive and you will be assured of many more years of leak free performance, plus better winter heat.

The job is not difficult, UNLESS you have factory indash AC.

One of my many bad driving experiences while driving my 66 couple over bridges or causeways during the 70's was a sudden heater core leak of fluid and steam into the interior of the car. This happened on the 10+ mile long San Mateo-Hayward bridge near San Francisco. I had to continue driving a couple of miles until I reached an emergency turnouts. Luckly, I had one of those system flush fittings (a Prestone product) inline of the heater hose and was able to use this to bypass the core. I left it that way for a long time. +1 for tool kits.

Change the restrictor (the angle fitting that comes out of the top of the intake manifold). I bet it's corroded away to nothing and no longer functioning as a restrictor.

The heater core swap is fairly easy. Disconect the hoses at the engine, pull the four nuts off the inside of the engine compartment that hold the heater box (the ones around the fan motor), unplug the two motor wires, unplug the underdash plug to the heater box, unbolt the one bolt at the cowl vent, disconnect the control cables, remove as one assembley. You can do it in about twenty minutes if you don't have AC if you're slow. You can do it in five after you've done a couple.

CraigMBA said:

Change the restrictor (the angle fitting that comes out of the top of the intake manifold). I bet it's corroded away to nothing and no longer functioning as a restrictor.

The heater core swap is fairly easy. Disconect the hoses at the engine, pull the four nuts off the inside of the engine compartment that hold the heater box (the ones around the fan motor), unplug the two motor wires, unplug the underdash plug to the heater box, unbolt the one bolt at the cowl vent, disconnect the control cables, remove as one assembley. You can do it in about twenty minutes if you don't have AC if you're slow. You can do it in five after you've done a couple.

Click to expand...

This is all very good info from CraigMBA! The job is not hard, but allow a couple of hours to do it since you haven't done it before.

Also, once the assembly is on the workbench you will need to snap the 10 or so metal spring clips off the box in order to separate the 2 halves to get at the heater core. Not hard with a screwdriver, but be careful as the heater core box assembly is fiberglass and can be broken if you are not being careful.

You may find that the seals in the heater box are bad and you may want to replace them too--available through most Mustang vendors as a kit.

Once you have the box back together, install and clamp your NEW heater hoses to the heater core BEFORE putting the heater box back into place under the dash. You can match the length of your old hoses, if they look right, or add slightly longer hoses and cut to length on the engine compartment side once the heater box has been reinstalled. The hoses are 5/8" in diameter. Buy a good brand of heater hose from Napa or other trusted source. Don't use the crap hose-in-the-bag from Advance Auto as it is thin and will certainly lead to premature failure. I also recommend using good screw clamps vs. the original factory clamps, especially on the heater core since they are nearly inaccessible once the box has been reinstalled.

I tested my new heater core before installing it. I went to a local bicycle shop and asked them for an inner tube from a 10 spd style bike. They guy gave me one that had a hole in it. I cut it up and connected the cut ends to the tubes of the heater core. Taking my trusty bicycle pump I pressurized the core while it sat in a bucket of water. No bubbles and no leaks.

You might consider having extensions soldered to the core, you could have the tubes extended enough that the clamps could be in the engine compartment rather than inside the car.