huh???? Engine rev up/down when I hit the break

[Guest xbangu]

Hi,

I got a 240Z with a 280zx turbo engine it in. First thing first, it took half a tank for a 10 (ten) miles trip. Found out that my return line leak and sprayed all over the engine compartment. Got that fix.. then suddenly, when I "hit the break" the engine rev up and dow between 1.4 to 1.7 huh??? any one have this problem before??? Does the break have anything to do with the air intake???

 

PLEASE HELP!!!!!

[Tim240z]

Look for vacuum leaks at the brake booster.

[Guest xbangu]

Also, when I hit the brake from sitting in the driver side.. I can hear a hissing sound of air leaking and my brake take more distance to get in a complete stop. What does this sound like, could this be the master brake cylinder bad?? or just one of the hoes is leaking???

[Thumper]

It is either the brake booster vacuum line or your brake booster itself leaking. While you are at it make sure your one-way check valve is working correctly. Check these three things out b4 you try anything else.

[Tim240z]

It won't be the master cylinder, but rather the booster.

Take out the vacuum line that goes into the booster and plug it. Retest brakes with engine running (they will be harder to push because of no boost assist). If there is still a rpm change and 'hissing' sound then the tube is broken. If not then you need a new booster....

[Guest xbangu]

thanks for all the help guys, I replace the booster and now my brake is workign good.. maybe need a bit more leaking to get it at it best.

 

once again thanks!

[Guest PEOPLES805]

Thanks tim i just searched for this Exact problem and confirmed what i thought. I didnt event think of the ideat to pull the vacuum line from booster . thanks again