Hey fellas, what is that horizontal black metal tube along the firewall in the W123 300D? It's about three feet long and about 3/4 inch diameter.

I dropped my car off for a state inspection and mechanic said that tube looks like it's leaking coolant. I didn't think that tube had any coolant in it. I'd go look at it but I'm 200 miles away lol.

I figure the coolant has come from somewhere above or forward of that tube and dripped or blown onto it.

But the I realized I had no idea what that tube does.

Thanks!

Jim