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Replaced Brake vacuum line, pedal pulsing.

Old 10-19-2011, 04:21 AM
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Replaced Brake vacuum line, pedal pulsing.

1978 280Z. Stock front discs & rear drums.

So, I've been going through little by little replacing "suspect" parts. My brakes seemed very soft through about half-travel then gave good resistance from there. Car stopped fine, could lock brakes even.

Due to the fact there were four pieces of line, a pressure (why, no idea, didn't read anything) gauge making up my brake vacuum line, I thought it was worthy of replacing. Vacuum line ran from the rear-most intake tract to the MC, new line follows same path.

Now, I can feel distinct intake pulses from the intact tract in the pedal. Feel is more linear than before throughout pedal travel. Am I supposed to feel the intake pulses? Should the vacuum line pull from more than just the one intake tract to smooth out feel?

Thanks for the input folks!

JM
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Old 10-19-2011, 10:08 AM
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Intake pulses??? Unless your motor is running really rough, and the rpms are jumping all over, it's not "intake pulses".

Do you have slotted or drilled rotors? Are the rotors new? Does the steering wheel vibrate when braking?
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Old 10-19-2011, 10:49 AM
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No vibes when braking. Sitting still, I can feel each time the engine draws on the #6 intake tract. Rev the motor, I can feel the pulse get faster until it's so rapid you can't feel it any more. Running standard discs too.

After a little research, it seems I could have removed a check valve somewhere when I pulled the old line off. I've got to check on that when I get home. I'll report back if that was the problem.

JM
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Old 10-19-2011, 11:50 AM
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Ah yes... there is a ball check valve that must be on the line, otherwise the booster would just leak down. Good find.
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Old 10-19-2011, 01:49 PM
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That was the problem. I'll be putting that back in now.

Drove to work this morning, it was definitely the check valve missing causing the pedal to pulse!

JM

Last edited by the_journeyman; 10-20-2011 at 04:15 AM.
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