> I have a '73 Datsun 240Z and am having some
> trouble with the brakes. Without the vacuum
> assist the brakes are VERY heavy but work
> fine, about like brakes should work without
> vacuum assist I guess.... The problem comes
> with the assist hooked up. The pedal is as
> light as a feather, it travels half way to
> the floor without doing anything, and then
> in about a 1/2 inch travel the brakes nearly
> lock up! Very annoying. I put a new master
> cylinder on have bled all of the brakes with
> no improvements in my problem. Any ideas out
> there?
Hey there. Well I am having just about the same problem. My pedal had no feedback or resistance. When you push far enough, it almost puts you through the windshield. I changed my master cylinder and bled the system to death as well. I suspected a faulty booster, but was told by a reliable source it is probably the proportoining valve. I have not had time to try this yet. Also, make sure your brake lines are in good condition. If they are old, they may expand and cause similar problems.
Good luck,
Jason