I noticed that this was missing on my '85 when I did the water pump, and then promptly forgot to look for a replacement till now. My temps are fine how important is this to the efficiency of the cooling system?

Breather tube, cooling system (water pump to head)
MB# 115 200 00 58

I'm ordering this part when I can find the crush washers. My search skills are weak on Peachparts.

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1985 300D-189k The 'UD', Ivory and Pinkamino
1979 300D-211k Dark Gray, Parchment
A 1980 Harley-~166k and
A 1994 Ford diesel pickup-349k and
A 1990 gasser Volvo wagon-145k