Wednesday, 22 February 2012

Brake Replacement: Master Cylinder Troubleshooting for Brakes!

Are you feeling a bit uneasy when your auto mechanic recommends a brake replacement because the master cylinder on your brakes has failed? How can he tell? Or is he just trying to sell you an add-on job to the other repairs on your car. How do you know if he is doing his job correctly and looking after your best interests and your safety, rather than taking you for a ride with a brake replacement?

If you are looking for expert mechanic Princeton MN your search can be over with our Rum River auto center Princeton MN. Find us for vehicle suspension Princeton MN and vehicle maintenance.

Master Cylinder Troubleshooting Tips:


One sign that a master cylinder is starting to fail is that you will notice a soft or squishy feeling when you press down on the brake pedal. As constant pressure is maintained on the pedal (like at a stop light), it will begin to sink to the floor as the brake fluid leaks internally to the master cylinder. This is called "extended travel." You may have to "pump" the pedal to regain normal pressure and keep the car from moving forward as the brakes slowly release. The red warning dash light should come on to indicate low fluid, or excessive movement "travel."

The fluid level alone isn’t an indication of a good or bad master cylinder. Typically, the leak is internal, leaking past internal O-rings, so there is no obvious external sign that the master cylinder is "bad."

What is another sign of a possible faulty master cylinder? An external fluid leak could be possible, and would be visible to a mechanic during an under-hood inspection. The master cylinder usually has a plastic reservoir that holds the fluid, mounted with rubber grommets. The grommets allow for some movement caused by the pedal and fluid pressures. These grommets can develop a leak that can be seen with the naked eye.

Another sign of a possible faulty master cylinder is that the metal lines attached to the master cylinder can leak fluid at the threaded connections, or from the internal O-rings. When this happens, the fluid will drip down the power brake booster (the booster is what the master cylinder is bolted to). Brake fluid will dissolve paint rather quickly, so this kind of leak usually leaves a tell-tale sign of blistering, bubbled paint.

If you experience any of the symptoms explained above, check the following:


  • Check the fluid level and add more as needed;
  • Make sure the cap fits snug and is not leaking or shows obvious signs of past leakage;
  • Visually inspect for external fluid leaks;
  • Wipe away accumulated dirt and debris for ease of future inspections;
  • Have your brakes inspected if more than 1 or 2 ounces is needed to top off the reservoir;

Are you looking for professional advice on your brakes? We will be glad to help you. Contact our ASE-Certified Technicians today for transmission repair and advice today by calling (763) 389-3811, or go on-line at http://www.rumriverauto.com/ for more information. Since 1997, our auto repair shop has served vehicle owners in Princeton, MN, and in the surrounding areas of Milaca and Zimmerman, MN.

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