68 mustang - replacing the heater core
 

Hey folks,
I'm trying to search the web to figure out the process for replacing the heater core.... my 68 starts blowin moisture out of the dash shortly after it warms up. I have the new core, I just cannot figure out how to get at it in the dash.

I have the glove box out, but that's as far as I got, lol. If anyone has tips/tricks/how-tos on doing this fun little project, I would greatly appreciate your time to help point me in the right direction.

I'm fairly adept at projects like this, as long as I have something to follow for the first time, lol. car specs are below if it matters, I can post photos if needed of the dash area:

68 mustang fastback
289 V8, 3-spd manual
no A/C

Thanks in advance.

No AC means it'll be easy. Although if it was a factory AC '68, it's almost the same, with the excption of having to also disconnect the evaporator core, meaning evacuating the A/C system, then detaching the hoses as needed for that, then proceeding as shown below.

Disconnect the hoses from the firewall side. However you manage to do that and not leak coolant about... a bucket is advised. :)

There are 3 or 4 nuts in a squarish pattern about the fan motor on the right side. Take those off, they are literally all that's holding the heater plenum in the car.

The plenum is then attached to a few cables for temperature, inlet, and bypass control (floor or windshield, that). Disconnect these, be mindful if they're close, perhaps color coding which is which on the plenum and cables.

The plenum otherwise just slips on out. The heater core is inside the plastic plenum, and the plenum is held together with a bunch of clips.

BE CAREFUL with the clips when you take them off. If you damage the plastic, you will never get a good seal with them. Take your time. A large screwdriver positioned just so will spread the clip apart so that it may be pried off without much pressure otherwise.

You'll see how the old core is in the plenum. Orient the new core in there, and be sure to replace any weatherstripping/padding/? in there too.

Installation is reverse.

More instructions are out there, Google is your friend.

Good luck!

Thanks Houtex for the quick reply, I'll follow up with a status as soon as I get to take a look with your directions.

much appreciated!

There is one more fastener holding the heater box up to the cowl. Look inside the glove box opening up to the right. It's a 2" long sheet metal screw with a 3/8" head. Remove this or you'll end up breaking the box trying to force it out.

Oooh, good catch, Ken. Sorry about that! Memory's a bit... spotty I guess is the word... been a while since I done this thing myself.

Just be gentle, p. No gorilla like force is needed in any of these doings. Be sure it's all loose and not binding up somewhere. :nice:

well I made a little progress tonight, lol... would still be out there but the darn mosquitoes got the best of me! anyway, I was able to get the housing loose, and took forever to find that under-dash fastener... because it wasn't there!

Anyway, all that's holding the box in now are the hoses... I'll get those off this weekend....

Thanks for the tips everyone, everywhere I called for this quoted $350 to replace this thing... glad to know I can do it.

Thanks again

They want $350 for this?! :shame:

Then again, if it was Pep Boys or something like that, then... yeah, makes sense. :p

/Bad experiences at one.
//Others weren't bad, but that bad experience was a heater core, and they *tore my dash and console up* in my '87 Mark VII.
///I had them replace it and give me a rent car for a month while they repaired their gorilla actions. So they made good, but still.

not a pep boys, I had quote from pretty much everywhere within a 30mi radius, from dealerships to small town shops. It's really hard to find a trustworthy shop anymore.

finishing my coffee and off to finish the core job.

Thanks again for all the help.

Discovered the holes in the box don't line up well with the lines off the heater core, and looks like the person who did this previously had the same issue, as the plastic lip/edge of the box is broken around the area of the holes. I can get the core lines in there, but they're pushing on the broken plastic a bit.... bummer.

putting all the new seals on everything now, hopefully when I put this back together I can place the clips carefully enough to help reinforce this area.... at least until I can afford to get a new heater box.

After a few interruptions, I finally have everything back in place :banana:

silly me, I forgot to make note of how the hoses hookup in the engine bay.... can somebody tell me how these should hook up, or does it matter since it's really just a loop?

Thanks

You're right, it's a loop, it's going to go in and out either way. Make it look pretty/right in the engine bay, and you're good! :nice:

You've probably already done it, though. :) Did ya have fun with it? And... well, I'm just curious. Do you think it's worth $350? :heh:

thanks for the confirmation Houtex, yes I tightened everything back up and went for a test run, no more leaks and fog! Big thanks to you and Kennyg.... if anybody is deciding whether they can/should do this or pay for it, all I can say is do it. The hardest part was putting the box back in position and getting the bolts back in the firewall holes, since I didn't have anyone to help eye it up from the engine bay side.

anything that can be done and save a trip of putting my car in the hands of others is worth the time and effort :) and I can take my wife out with *some* of the money I saved, (the rest of course can find a way back into the mustang) lol.

The way I always remember which way the hoses go on a 289 is top to bottom and bottom to top. I also loop the full length of hose and push it through the firewall and connect it to the heater core, then cut the hose when I'm ready to hook it to the engine. I flow diagram in the service manual shows the routing I described. FYI