201 brake pedal suddenly hard - PeachParts Mercedes-Benz Forum

lanny · #1 05-10-2012, 06:50 PM

Hi guys, today while driving i was approaching an intersection i applied brakes as per normal the pedal got really stiff, i almost pass out when that happened, luckily my reaction was to release the pedal and apply it again. this time the brakes worked as it should.Has anyone out there experienced this happening to them? and what caused it?how to prevent it from happening again.

thanks for your input.

280EZRider · #2 05-11-2012, 12:21 AM

I don't know exactly what you are saying here, but if the fluid has moister in it, this could cause pitting and rust on the pistons and caliper seats. It's possible that enough rust or pitting caused one or more of the pistons to stick just this one time.

teezer · #3 05-11-2012, 09:01 AM

in most cases where the pedal is hard with the engine running, it's related to the brake booster ~~~ look for a vacuum leak on the feed to the booster tank, or possible booster diaphragm tear, which is inside the booster tank

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lanny · #4 05-11-2012, 10:51 AM

Thanks for your suggestion EZrider & Teezer.I replaced the brake booster in january and i know the gasket is good,for the brake caliper i replaced the left front with a used one as the original was frozen.Do you think the booster vacuum line could be the culprit then.more suggestions please.Thanks

JamesDean · #5 05-14-2012, 02:08 AM

As it was said previously, normally hard pedal = lack of vacuum. Perhaps you have a vacuum leak somewhere that come and goes?

Check on that replaced caliper, maybe it is giving you some issues.

When was the last time you flushed the brake system out?