Date:         Wed, 19 Jul 1995 15:54:05 CST6CDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         "Dan Houg" <fairwind@northernnet.com>
Subject:      brake break-in

John says:
> One other thing - while test driving and test braking I noticed that a
> rapid series of hard pumps on the brakes seems to disable the front disks.
> Hard stabs at the pedal about a second apart gives seriously degraded
> stopping on the third shot.  Lots more pedal pressure required as well.  Is
> this fade? (shouldn't have had time to get hot, and if I ran for a few more
> seconds and then hit the brakes once hard, the front brakes work fine)
> What could be making the front brakes quit working?

Hold on there, pardner!  Under ideal conditions, brakes should be 
given a slow break-in period to bed shoes/pads to their friction 
surfaces.  Too vigorous application too soon can cause (now for the 
worriers in the group) resins to boil out of the friction material.  
Freshly surfaced drums/disks and new pads have extremely high 
coefficients of friction and generate lotsa heat.  Bed new brake 
components by gently slowing down from 30 mph and allowing a minute 
or two between doing this to cool things off.  repeat many times.

Now, i don't know anyone that does the above, including me.  After 
putting new brakes in i mash on the pedal to see how 'good' they are. 
 Don't worry, you haven't done any real damage.  Just had to make you 
worry like the rest of us!

Sounds like your brake booster is leaking vacuum upon application.  
when you give it a few seconds, it has time to regain vacuum.  i'll 
try to see if i can find an earlier post i'd made re: diagnosing 
boosters-- watch for it.

-dan