hi driving my 1988 107 sl my brakes suddenly failed after pumping the peddle they resumed to proper order..anybody had this problem.....thanks

 

WELCOME to the forum.
Sure sounds like an item is by-passing.
Fluid level is full?
Check the brake master cylinder as well, you may see brake fluid between the BMC and brake booster.
If it were my car, I'd replace the brake master if I found no other leaks.
To find a problem that no longer exists is tough but with brakes you need to be sure you've isolated the issue.
I like to install a block at junction points and test until I no longer get a by-pass at the pedal...of course you have to have a failure while testing...