Unknown humming sound?

[mabryt]

Hi Oscar,

Thanks very much for the attentive reply.  I'm taking the Green Goddess into the shop tomorrow along with a print-out of your comments.  I'll report back with an update.  As for locating the sound, it actually DOES sound like it's coming from under the hood.  I admit, however, that I have no idea what is meant by a "Brake Booster."

Much appreciated, Oscar!

[oscar]

what is meant by a "Brake Booster."

This thing, right in fornt of the driver and usually painted black, not custom rust like the one shown.   Good luck

[mabryt]

Ah hah!  That's what I call the brake servo, but actually I think brake booster sounds much cooler.  Thanks for the pic- worth a thousand words.