I have a 99 TH Magna Wagon and have discovered soon after I purchased it that the heater core is not connected. This is something that people tend to do to stop their feet getting wet if the core has corroded. Since then I have heard that it is very difficult to replace the core requiring the dashboard to be completely removed. Has anyone attempted to fix this issue in their cars and, if so, how hard did it turn out to be?

BrisbaneLad

Hey mate.
First of all, welcome to AMC. I've seen you only have two posts, I hope to see you around more.

In regards to your post:
My heater core did the same thing as yours about 2 months ago. Basically, the whole thing was leaking coolant into my passenger foot-well. It almost killed my ECU, I was pretty lucky haha.
Now I called up Mitsubishi and some other service centers, and received quotes of $700+ to get it fixed, some of them PLUS PARTS. I ended up taking it to Mits-fix, which is a business run by one of the admins on this forum who is also a mechanic. Probably the best mechanic for Magnas in the whole of Australia. He quoted me $550 to replace the core, including labor which was a hell of a lot cheaper than everyone else. He let me hang around the whole day whilst he did it and it was a hell of a job.

You need to talk out the whole dash (including steering wheel, airbags, etc). After that you have to take out your climate control/air con, stereo, center console and a LOT of mounting brackets to actually get at the heater core. Once you take it out, you need to replace it with a new one (which you'd have to order from Mitsubishi or, for a cheaper price Mal (the owner of Mits-fix).
To be honest, unless you are very comfortable taking your car apart, and are willing to not be able to drive it for a day or two (depending on how much time you have to spend) then I'd look at getting a professional to do it. Unfortunately I can see you're located in Queensland, Mits-fix is in Victoria. So unless you're down here anyway, probably wouldn't benefit you too much haha.
My advice is to just call around a get some quotes, then make a decision.
If you think you can live without a heater in winter, then don't even worry about it, just make sure that when the previous owner has bypassed the heater core, they've reattached the pipe securely.

Hope that helps!