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post #4 of (permalink) Old 19th January 2013
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Re: Flipped Seals on master cylinder - Megane

In my experience I have never actually seen master cylinder seals flip although it would be great to see a photo of such.

With the servo empty how much brake free travel is there in the brake pedal and is it firm when pressed?

It may be the caliper pistons keep retracting and not remaining in position against the back of the pads. If you clamp the front flexi hoses and the pedal improves then this would prove if the problem is at the master cylinder or at the caliper.

I have came across this problem on a few occasions. Once on a Megane and another on a Honda Accord. I dismantled the master cylinder on the Megane numerous times but could find no fault. I them clamped each flexi-hose and the pedal was fantastic. I then got someone to fully depress the brake pedal and then clamped the hoses and got them to release the brake pedal slowly and watched the brake level drop. I repeated this 3-4 times at each wheel and the brake pedal returned to normal. This had the effect of preventing the caliper pistons retracting.

You can use a pair of vice grips as a clamp as long as you use a heavy piece or cardboard or the like in the jaws to prevent damage to the rubber pipe.
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