My mechanic has just been putting in a reconditioned brake booster in my WB van. He is going to take another look on Friday as he didn't have time to finish the job completely yesterday.

When the brakes are applied via the pedal, it has the feeling of a notch in the actuation about 2/3 of the travel of the pedal.

Any ideas to what this might be? The issue wasn't there prior to new booster fitment? Just trying to troubleshoot it.