drdantheman1

Hey everyone, quick question. I just had my brake booster replaced (due to an airhorn type sound) and per my SA, they had to bleed the brakes along with it according to the mercedes manual. Since then, the pedal feel is about 10-20% softer than before. Just wanted to know if that's something normal to expect with a new brake booster, or if that's just a result of a poor/rushed brake bleeding. Any input is appreciated.

Thanks!

KEY08

Mud

^^agree, worth mentioning to SA.
From the description the old booster was leaking air and therefore the pedal would feel harder to push but you were used to that.
The new booster is providing more pedal assistance, something you are not used to yet. However final pedal "limit" so to speak should be firm and not spongy.

drdantheman1

I went back to the dealer ( on a rainy day) and the tech did a test drive and activated the ABS system. He then bled the system again afterword. He said that in his opinion, the brakes not only feel normal, but actually better than most of the E-class that he works on. In my opinion, the brake pedal improved every so slightly but still feels different than before. Prior to the new booster/fluid flush, the brakes felt firm and high. After reading a bit online, it seems that's actually one of the symptoms of a bad brake booster. Now, the brakes feel a little longer and more progressive (less grabby/touchy).

Does your e-class brake pedal feel the same?

Mud

Well its subjective but my brakes are progressive but not grabbing. Pressure feels firm and then at full stop pedal stays firm. Bear in mind I've installed new pads, rotors and I've re built the calipers plus fresh fluid. So I expect good braking!
I think your brakes should be ok just different feel. Boosters have a rod that connects pedal to master cylinder, even a mm or two can cause different pedal feel/height but braking effectiveness would be fine.

drdantheman1

Just to close up the thread, I actually ended up taking my car to an indy tech after the dealer visit. The owner used to be a service tech from the SAME MB dealer I use for my car for 15 years, and knew exactly the service/procedure they had done. Basically he told me that even though they have the right tools, on occasion, they can rush through the bleed procedure and not adequately get all the air out. About an hour later, he had the brakes adequately bled and now they feel great!

Arrie

KEY08

Arrie

Just a comment here...

There is something going on with the timing of the posts. When I wrote the above reply there was no post from the OP where the solution was explained, which is exactly what I posted about, i.e. poorly bled brake system. In fact, I posted my reply a day earlier than what the date stamp says.

Not a biggie but makes me look like an *** with a post dated later than what the OP posts was the solution.