How long should a brake servo hold / store vacuum? Driving along today at normal speeds I brake for a car turning right in front of me. No problems with braking. Once the car has turned off and is out of my way I gun it through 1st, 2nd and into 3rd. At this point I notice a farmer potentially about to pull into my path out of a gateway so I hit the brakes. For a moment, there is no / very little assistance. Upon rapidly releasing the pedal and re-applying (once), full braking force is achieved. Is this normal, or have I got a split somewhere leading to the servo? In normal driving I spend a lot of time in vacuum, so it may have always been like this, and only now, when requiring the brakes after a full boost run have I noticed it. Thoughts? Edit to add - BAM, 2003 S3. It still retains the original 1 way valve at the bulkhead, plus the additional one I installed months ago at the inlet mani.