Jump to content


Pressing brake pedal increases RPM

Jon, the BIG boy

Recommended Posts

Got a brake problem, probably vaccuum.

'72 240Z

Brakes work OK--plenty of pedal. But all braking power assist is gone. When pressing brake pedal, I notice an low hiss (like a leaking air hose) under the dash and the RPM kicks up by 1000 RPM. Opened hood and noticed liquid (brake fluid?) just below the master vac brake cylinder.

Has anyone had this problem? Trouble shooting section of manual says nothing about the increase in RPM. I'm guessing I'll have to replace the master vac, but will await any suggestions from this illustrious group.




Link to comment
Share on other sites

I would check the vacume line that runs from just below the master cylinder on the master vac. It runs (or at least should) to your balance tube on your intake manifold. Mine was pretty worn and needed replaced.

Have you done any mods? Not all the balance tubes have the same diameter for this vacume tube. Check it. Fluid you say? Possible you have a bad master cylinder or master vac but I doubt it. There is the possibility that brake fluid is leaking and geting hear the carbs, which I'm told WILL increase RPM. It is, after all, a combustible substance.


"Go into emptiness, strike voids, bypass his defences; hit him where he does not expect you" -Lao Tzu

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Who's Online   2 Members, 0 Anonymous, 169 Guests (See full list)

  • Create New...

Important Information

By using this site, you agree to our Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.