Sybill the SDL does a similar whoosh at cap removal but I drive that car so infrequently that I've been unable to determine if it is vaccum or pressure...I was thinking it was pressure but, on further reflection, that doesn't make any sense. It would almost HAVE to be a vacuum.

There's SO much wrong with the SDL...

Lilly the 300D apparently had a plugged breather but I never knew it until I pulled the tank recently for anti-fungus scrubbing and treatment. Lord only knows where it was equalizing the pressure...the cap probably.

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Never a dull moment at Berry Hill Farm.