if your brake booster is bad and is replaced, does the master cylinder need to be replaced also?

Asked by brown200 Jun 08, 2015 at 05:17 AM about the 2007 BMW 5 Series 525i Sedan RWD

Question type: Maintenance & Repair

My brakes became stiff and hard and I was told that the master cylinder was bad.  They replaced the booster and not the master cylinder.  When I picked up the car the pedal went all the way to the floor.  The shop leader said it was because the brakes needed changing.  I changed the brakes only to find out that did not fix the problem.  I took the care back to the shop only to hear that the master cylinder is bad.  Should they know this when they replaced the booster and why did they not replace the master cylinder as they said they were going to the first time?

4 Answers

23,920

These are all very astute questions. I really feel, after reading them, that you have multiple problems in hindsight. a hard pedal can be caused by pads effectiveness, Their lining condition, material makeup. and condition of rotor surface A hard pedal can be caused by caliper issues. It can also be caused by a failed brake booster, leaking booster, or insufficient vacuum or vacuum volume, a failed vacuum check valve, The fluid can leak from the master into the booster. Why did you have a loss of pedal after the booster was replaced? instead of the hard pedal you had before? perhaps boost was restored, and your symptom's feel changed. perhaps they opened the hydraulic system allowing air to enter? You would have to test each time you changed something or received the car from them. Worn linings, if that's what you found, needed replacing. they can cause low pedal. Bleeding the brakes after is normal maintenance to have fresh fluid and getting the old "wet" fluid out. That should restore your pedal if air is trapped. If your system requires a bleed tool for ABS, you may want them to continue till they have a pedal, or replace the master and bleed it to restore a good pedal. When you have that....You can trust your brakes. You always have the option of a German car shop or a brake shop to verify the findings told to you. The circumstances seem strange the way you describe them... but you have to get your facts at that moment, to draw any conclusion. We cannot do that from here.

1 people found this helpful.
23,920

The one other anomaly, is allowing the pedal to bottom out, during parts replacement. That can hurt seals. pedal bleeding would have just been needed if they were replacing the part you say is now failed but was not replaced. so, did they maintenance bleed it? we cannot see that either.

10

I'm having a problem with my 745 BMW someone please help it's telling me that my brake liner is broken so I checked it out is this the reason why my vehicle doesn't start

1 people found this helpful.

2008 750Li. Had a yartd ech help, or tutored while he made the attempt, repaired several other things meanwhile. Brake peddle locked. Can't start unless I pull the pin from the peddle to the booster. Sensor move's, car starts. What did the kid do wrong? Is there a keepr not takene off, what do I check for? Bleeding the abs?

Your Answer:

5 Series

Looking for a Used 5 Series in your area?

CarGurus has 321 nationwide 5 Series listings starting at $4,500.

Postal Code:

CarGurus Experts

  • #1
    Michael Branan
    Reputation
    1,400
  • #2
    Robert Charlson
    Reputation
    1,050
  • #3
    apbimmer98
    Reputation
    950
View All

Find great deals from top-rated dealers

Search

Related Models For Sale

Used BMW 3 Series
71 Great Deals out of 1,176 listings starting at $1,995
Used BMW M5
56 listings starting at $26,800
Used BMW 7 Series
9 Great Deals out of 119 listings starting at $5,995
Used BMW X5
47 Great Deals out of 1,134 listings starting at $3,995
Used Mercedes-Benz E-Class
30 Great Deals out of 496 listings starting at $5,700
Used BMW M3
8 Great Deals out of 90 listings starting at $15,995
Used Mercedes-Benz C-Class
98 Great Deals out of 1,455 listings starting at $3,799
Used BMW 6 Series
5 Great Deals out of 63 listings starting at $6,800
Used Mercedes-Benz S-Class
15 Great Deals out of 227 listings starting at $8,977
Used Dodge Charger
38 Great Deals out of 645 listings starting at $4,888
Used BMW X3
43 Great Deals out of 1,013 listings starting at $4,995
Used Audi A6
5 Great Deals out of 117 listings starting at $3,950

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use. Content will be removed if CarGurus becomes aware that it violates our policies.