I have the exact same problem. By "cowl" do you mean the firewall? It appears, possibly, that this area of the firewall is removable.

How do I remove this, or get into this area so that I can replace the hose?

Thanks

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1994 C280, dark green metallic
105k miles

1991 190E 2.6, Black
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(sold to another forum member)

2003 Chevy Tahoe LT, Redfire Metallic
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1989 Mustang GT Cobra Convertible
43k miles