I would like to suggest that you check the radiator cap itself. Make sure the rubber is still in good shape, and that the spring is still in good shape. I had to replace the cap on my W124 after only getting 89k mi. out of it. (I also noticed corrosion on the cap, and on the brass neck on the tank)

-Larry

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D