I'll bet you've got air in the system somewhere, and it is finding the high point in the system, which is the upper radiator hose (which sits higher than your expansion tank on that car). I did the exact same thing with my C last summer, I had my indy replace every radiator hose under the hood. Before he sent me away he basically "burped" the system for me to make sure it didn't have air in the lines. You might have to get this done. I didn't pay close enough attention to see what he did, so I can't tell you. Maybe someone else here can offer some advice on that.

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Jonathan

2011 Mazda2
2000 E320 4Matic Wagon
1994 C280 (retired)