I recently found a nice dash for my 300td, and I've been thinking of any while-I'm-in-there work I should do. I've had a heater core fail on me once, and it was miserable to clean the mess and do the R&R, so I thought I'd replace the heater core in the 300td before it fails. It has 328k miles on it.

I just looked through a few online vendors and it's apparently NLA. What can be done? I tried searching here but didn't find much. I guess w123 heater cores don't really fail that often? I read a couple times about circulating stop-leak through the core as a quick fix, but I'm more interested in an actual replacement.

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'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo