[honeymonkey]

has anyone an idea the cost involved and how badly your mechanic put your dash back together?
thanks,
HM.

 

[AndyEckel]

This is a broad question. You should get a a bunch of good answers with a variety of suggestions. In the meantime, I hope this general info helps:
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Replacing the heater core on pretty much any Mustang since around 1991 is generally considered one of the two most detestable jobs that needs to be performed. The other being a complete timing set replacement.
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Replacing the heater core essentially involves draining the entire coolant system and AC refrigerant system, because they are intertwined, disconnecting all the hoses in the engine bay, then removing the entire dash, center console, radio, steering wheel and all the associated components. It is time-consuming and tedious and is best done by someone who has actually done it before or by a skilled tech who has access to Ford technical procedures and knows what they are doing.
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At any competent shop or dealer, the time you will be charged to remove everything to gain access to the heater core will be 4-5 hrs of shop labor. Minimum. It is just an awful job and a lot can go wrong depending on the level of corrosion and vehicle condition. This is what it will look like.

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At this point, there are two primary differences as to which way to move forward.

1) Ford's standard procedure is to replace the entire assembly that sits inside the car, behind the firewall, on top of the transmission tunnel, just below/behind the dash, in front of the shifter. This whole assembly contains the heater core itself and the AC evaporator core plus other internal components. It is about 25 lbs and looks like this. Ford considers this entire assembly a sealed unit and "not serviceable". This is about a $500 module online.

2) Despite Ford's stated procedure, the above unit can indeed be taken apart to replace only the actual heater core inside. Note the heater core itself is only about $45 and is shown below. That being said, disassembling that entire unit requires drilling about 15-20 plastic rivets, keeping track of internal components such as O-rings, and then putting it all back together - correctly - with / or without replacing the AC evaporator core which is also inside. Hardcore enthusiast DIY'ers will take this approach. Shady shops will tell you / sell you the entire assembly for $500 and yet only replace the $45-50 heater core. You need to understand which approach they will take. This is where shop / dealer integirty and honesty enter the discussion.

Given the overall invasiveness of the entire procedure, and the possibility of something going wrong, I would not recommend just hacking it apart to replace the heater core. I would replace the entire unit. This is not a job you ever want to repeat.

3) Re-assembly of everything, in reverse order of above, is another 4-5 hrs of labor.
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All In Costs at a Good Shop or Dealer
8-10 hours of labor and $500 in parts for a job done correctly
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If you can do it yourself, you can save a $$$$ of money.

 

[honeymonkey]

Ok, this is scary stuff. Mine is not leaking much, I can just start to get a smell. Of it when the fan is turned on. Don’t notice any coolant missing. Trying some kseal may be my first move.

 

[AndyEckel]

I would personally avoid using any type of liquid sealant additive. They just clog things up and result in an internal gummy, gooey mess.

I would, however, try some UV dye in your coolant to help you pinpoint the leak source. It could just be a hose fitting right at your firewall. This stuff is like $10 a bottle and many people have success with it. Make sure you pick up a UV flashlight.
Auto Pro USA Antifreeze and Coolant Leak Detector UV Dye 1oz (autozone.com)

A pressure-test of your system might also be of help.
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In other words, I would do everything possible to disprove it being the heater core leaking. Good luck

 

[Cobrajet67]

has anyone an idea the cost involved and how badly your mechanic put your dash back together?
thanks,
HM.

Ok, this is scary stuff. Mine is not leaking much, I can just start to get a smell. Of it when the fan is turned on. Don’t notice any coolant missing. Trying some kseal may be my first move.

Like mentioned, the leak could be from a heater tube connector that's leaking in from the engine side of the firewall and then down into the heater box. The connectors are only made of plastic and seal with an o-ring which have been problematic on other areas of the cooling system that use these plastic parts. I'm pretty sure that I've read of someone on here complaining about that exact scenario with an S197(2005-14) leaking right at the firewall connection.
I also totally agree NOT to use any kind of sealer if this is a heater core leak. It will clog up your radiator and heater core, etc and can foul up the thermostat, coolant passages, and sensors. It will likely make much more of a problem than you have now. Though the labor will be expensive it's the only way to properly deal with this problem. The coolant leak will get worse as time goes on.
Genuine Ford Evaporator - Ford Parts Giant

 

[AlloyPony]

Wouldn't it be awesome if the leak was found outside instead of inside? Man that would make me smile if I were in your shoes.