Brakes

I resently started getting a problem with my brakes, I think it is related to the brake booster but I am not sure.

my brakes have become hard and is not braking properly, normally this happens when the car is not running because the booster needs rotation from the engine to work, I am getting this even when my car is running, intermediately it comes back and then it's hard again....my brake fluied is fine....

Any ideas how to fix this, normally I would think bleeding the brakes would work but in this case I am not sure it would?

This on the ZX?

Maybe an air leak in the vacuum hose from the booster to the manifold, Also, there should be a 1 way valve, if thats stuffed then you are boosting into the brake booster.

what would the symtoms be if the check valve is not working properly....would the result be that the brake stiffens up, would the brakes fall away(brake paddle compress further than usual)?

I am trying to think what would make the brake paddle feel stiff and not able to compress?

What would the symtoms be if there is a leak in the booster pipe(vacuum pipe)?

Does the car idle higher when you press the brake paddle?

No...

Good then atleast the diaframe inside the booster is intack.

Are they sorted now?

it looks like it, there are 2 places on my plenum that allows vacuum, the one where the vacuum to the booster was connected seems not to have suffisiant vacuum anymore, so I shifted the vacuum to the second vacuum outlet, I am still going to remove the plenum to check why the previous outlet is not working anymore.

I tested the booster according to the manual and it seems that the booster is fine, but I have noticed now that it is working that if I compress the brake the idling goes up very slightly.

In older cars its is normal(not nessesarely right) for the revs to go up very slightly as long as it doesnt climb by hunderds of rpm.