Question about the power brakes on my '72 164e. Here's what it does sometimes...

Brake hesitation basically... I'll step on the brakes, and they don't do anything (as if the motor was not running) for a half second or so. Then they catch up, and work fine.

When it happens... Its happened only 3 times in the last month and a half. Every time was when I parked the car at a restaurant for lunch, so it was shut down for about an hour to an hour and a half. Always nice weather...but never too hot out, nor too cold. The first two times was at the same diagonal parking place on a highly arched road such that the passenger side front was way lower than the driver's side rear. The third time, the car was parked on a level surface.

My diagnostics... I only tried to figure the trouble out the first time. I figured it was a leaky one way air valve, or a vaccuum leak in the hose. Neither were the case. I pulled the hose to the booster and the engine revs jumped. I plugged the hose, and it fell to normal again. Then, after it ran for a couple minutes with the hose attached, then shut the engine down...then pulled the hose at the booster. Lo and behold, there was still vaccuum there. With the hose disconnected, I can blow or suck one way, but not the other...so the one way air valve seems to be fine.

So, my thoughts would indicate that the booster itself isn't leaking, nor is the line, nor do I have a vaccuum leak elsewhere. It always fixes itself after a couple stops (that is...motor of, then back on).

Because of the seemingly total inconsistancy of this, I'm at a complete loss. Seems like if something were going bad, it would do it all time. At least to some degree. But, as it is....it either works fine, or it has those symptoms...and fixes itself.

Any thoughts?

-Matt