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?
1994 C280, dark green metallic
1991 190E 2.6, Black
(sold to another forum member)
2003 Chevy Tahoe LT, Redfire Metallic
1989 Mustang GT Cobra Convertible