[350zwelgje]

Originally Posted by genpk

thanks mate, so your saying its just a normal state of affairs?!!
If so, great- ill move onto the next issue- brake dont have the bite they use to have, had new rotors 14k ago, pads look like theres still plenty of meat on them??

There is a valve in the brake booster. Think in haynes you can find a description for that and there is a also a one way valve in the vacuum line to it. Perhaps something is sticking/blocking. My son had this on his ZT190 and no braking. Checked/cleaned those valves, pushing the brake pedal a couple of times very hard and the issue went away. All ok now for a couple of months and a few thousand miles. Boosters can fail, master cylinders as well...

Another is that the brake fluid could have too much water content, but you probably would have had vibrations while braking hard before it got worse. Replacing brake fluid can never harm.

Rob