I'm pretty sure the pump(s) are on the outside, towards the right side of the tank. You should be able to hear them hiss when operating.
You're not having a vacuum going on inside of your tank, are you?
Are your filters clean?

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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