When i first get into my 98 E430 and step on the brakes they are hard. i think they should have reserve vacaum in the booster. is the small round device in the line going to the booster unit a 1 way valve. if so, how do i remove it to test it. could there be some other problem?

Is it hard after it sit's for awhile or right after you turn the engine off?

had not thought to check that. Thanks.