I just used the ciggarette butt trick to fix my tach but I did it with some foam from a shipping container. Anyway after i did this i took a look at my ALDA and There was a metal tube filled with some goo stuff that had hardened. This didn't look like it was meant to be there. anyone know what this is?

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W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.