Fox Mustang Heater Core Issues-Stop-leak work?

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As some of you may know, the Fox Mustang (79-93) is notorious for broken heater cores. The job of replacing them is very tedious. Dash, seats and center console have to be removed. Before attempting to tackle the job, would it be worth it to try some sort of a stop-leak like product?
 
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I'll probably catch some heat, not pun intended, but yes I would try a stop leak product if you don't have the time, money, or desire to do the job. Bar's makes some good products. I'd also look for a lower pressure radiator cap [if available for your application} and use it along with the stop leak product. Just make sure to run the engine with the heater on full blast if you use a stop leak product. Having said all that as you probably know, replacement of the heater core is always the best way to go.
 
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I know people that have used stop leaks and......at best it bought them some time.
 

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It does not require removing the dash, I've done two of them without doing so. I also would NOT try a stop leak product. Where they leak is usually at the solder joint where it goes into the core. That will eventually (and sometimes spectacularly) let go. Stop leak isn't going to prevent that. If you want me to detail the process of doing it without removing the dash, I can do so.
 
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I'm interested in the no dash removal procedure also. My friends got an 89 Mustang GT with a weeping heater core.
 
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A quick and dirty fix if you dont have the time or inclination to go through with what could be an awkward job is to locate the feed and return lines to the core in the engine bay before they go through the firewall, and use a tube or pipe of the correct diameter to link the two hoses together, removing the heater core from the cooling circuit. Its not correct but it'll do the trick in a pinch, probably better overall than adding some unknown hoop to the coolant given previous comments about the soldered joint letting go under pressure. I know a guy whose heater core burst and he still has the scars on his feet and legs.
 

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Originally Posted By: wymi516
I'm interested in the no dash removal procedure also. My friends got an 89 Mustang GT with a weeping heater core.
OK, this process takes about an hour or so start to finish. 1. Remove the glove box. 2. Remove the kick-panel on the passenger side 3. Remove the bolt holding the dash frame to the body beneath that kick panel 4. Remove the first couple of dash screws on the passenger side. You should now have a bit of wiggle room with the dash frame on this side. Switch to under the hood now 5. Remove both coolant lines from the heater core. 6. Remove both large washer/nut assemblies which hold the heater box assembly in. You should now have two almost threaded-rod looking things sticking into the engine bay Return to inside the car 7. Reach through glove box opening and pull/wiggle heater box assembly back, it should come in and you should be able to push it down toward the floor quite a bit. The bolts that go through the firewall will come inside the car. 8. Reach in through the glove box opening with a 1/4" drive flex handle ratchet and remove the bolts that hold the top onto the heater core. This is TIGHT. Be patient. 9. Remove the bolts and pull the top out through the glove box opening. 10. Remove heater core through glove box opening. 11. Install new heater core. 12. Install lid 13. Wiggle heater box assembly and heater core coolant lines back through their respective holes. This may take some cursing/swearing but it will go. 14. Reinstall heater box retaining nut/washers. 15. Reconnect heater lines 16. Refasten the corner of the dash frame with the screws and bolt. 17. Reinstall glove box. You are golden. It is a TIGHT job, but saves a MASSIVE amount of time over removing the entire dash.
 

Striker

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Maybe I am too particular, and I am not doubting your method. I'm concerned that with moving the dash board apart only from the passenger side, would it not bend/risk breaking something because the drivers side is still connected to the car? I know that if the car is NOT an A/C car from the factory, it is much easier as the evaporator isn't in there.
 

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You reach up with a wrench and take them out. They are accessible when you remove the glove box but you need to have the frame on that side loose in order to give yourself enough wiggle room to remove those and to lower the heater box assembly down. Forgive me from omitting those from my "guide" I posted earlier, it has been several years since I did the one on my buddy's '88.
 

Striker

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Lol you take payments in the form of beer and pizza?? Just kidding man, I appreciate the help. I'm just worried about the dash still being bolted down on the drivers side, and possible damage once being pulled forward. I will tackle this sooner or later as the rest of the car first needs to be scrubbed of undercoating.....I've never used more mineral spirits in my life.
 

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I love beer and pizza! LOL! Send me a PM, I don't like to divulge my exact location on a message board but we may be relatively close to each other. The dash is thin plastic and quite flexible, don't be concerned about damage, it will be fine. You only actually need to move it out an inch or two to give enough space to move/remove things. The biggest obstacle is getting the heater assembly out and down where you can get to the top of it, and then it is very tight to get the bolts out of the cover. A lot of blind work and you need a small 1/4" flex handle ratchet, but it saves so much time, as long as you can be patient and work with it, it isn't an issue.
 

Striker

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I have the whole winter so time is no issue lol. The center console will have to be removed too from what I read online. Not a big deal. I want to see what the deal is under the carpet. This car is a time capsule, almost too much of a survivor.
 

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Originally Posted By: Striker
I have the whole winter so time is no issue lol. The center console will have to be removed too from what I read online. Not a big deal. I want to see what the deal is under the carpet. This car is a time capsule, almost too much of a survivor.
I didn't remove mine, FWIW, LOL wink
 

Striker

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Ahh. If they don't have AC it is much easier to remove because there is no evaporator in the dash board/HVAC box. I took off my compressor too but the evap is still in there. Forget, either evap or condenser. One is in the engine bay.
 

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Yes, one is in the way and makes the job a bit more difficult. It is a lot easier on the non-AC cars. I think on the A/C ones you'd need to disconnect the lines, which would be a no-go with functional A/C. but since yours is not functional, perhaps it isn't as much of an issue, LOL smile
 
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