Q: master cylinder or brake booster

asked by on

hello, I need to know if I need to replace my master cylinder or power booster. when car is off I get a little hard pedal. when I turn it on the pedal goes to the ground. I have no brakes at all. I replaced the calibers, rotors, etc. and bled the brakes multiple times. I get good pressure from the front brakes when I bleed them and little pressure from the rear. which I am told is normal. I have no vacuum leek in hose coming from the booster. when I tried driving a short way ( I know not recommended with no brake ) I found that when I pumped the brakes real fast about 6 times I was able to stop. I have no brake line leaks either I checked that. when I disconnected the check valve in the vacuum hose I was not able to stop at all. my engine does not stall or even change in idle like someone mentioned in one of your post. If it was the master cylinder that was bad, I would think I would still have some brakes? your opinion would be greatly appreciated

If the pedal is low, there is air in the brake lines or the master cylinder has an internal leak. If your vehicle is equipped with anti-lock braking, you have to either bleed the ABS pump and valving (per Factory Service Manual instructions) or use a bi-directional scan tool to remotely actuate the ABS system during brake bleeding. Otherwise, in an ABS equipped vehicle air will remain trapped in that segment thus causing a low brake pedal. If you do not have an ABS system, the only explanation for what you are describing is trapped air, an internal leak within the master cylinder (of course look for external leaks, but you have done that already), or possibly bulging rubber brake lines. If you have a firm pedal and yet inadequate brake pressure at a wheel cylinder, that would be due to a proportioning valve fault and/or a line blockage. If you desire the brakes be bled by a certified Mechanic, dispatched by YourMechanic right to your location, please request a brake system inspection/diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. master cylinder or brake booster

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Q: Abs light on

The brake fluid reservoir is part of the brake master cylinder. It is located on the drivers side of the engine bay at the back on the firewall. The reservoir will have markings on it as to the maximum fill...

Q: Q: the engine turns over but wont start

You may have a distributor that is not giving off spark or the timing belt or chain has jumped timing and the valves are hitting the pistons. This is dependent on the vehicle and engine you have. Some are equipped...

Q: Brakes go all the way to the floor - 1998 Buick Skylark

To eliminate the possibility of air anywhere in the hydraulic braking system, you can bleed all wheel cylinders (calipers) even if you have worked on only one. Start with the longest brake line and finish with the shortest line. That's...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...