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Working on a friend’s car, has low brake pedal.

Home Forums Stay Dirty Lounge Service and Repair Questions Answered Here Working on a friend’s car, has low brake pedal.

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  • #581535
    TexarkanaTexarkana
    Participant

      The vehicle in question is 2002 Oldsmobile Aurora 3.5 V6.

      Last week I replaced the driver side CV Axle, and in the process of dis-assembly I found the top caliper guide pin bolt to be cross threaded, and while using a breaker bar to remove the bolt the outermost threads came out with it.

      Yesterday I replaced the caliper, pumped the pedal to set the brake pads and the pedal sinks all the way to the floor. I also heard a hissing noise as the pedal sank, although the pedal is stiff and doesn’t sink when the engine isn’t running so I figure the brake booster is working properly. The fluid was Ford’s green brake fluid, but due to contamination it came out looking like chocolate. I bled the breaks, RR, LR, RF, LF, until I got green fluid and no bubbles to come out.

      Took it for a test drive, the pedal sinks almost clean to the floor before the vehicle will stop. I took it out on a straight-a-way, and when braking from 30mph the car stopped fine despite the low pedal. The brake fluid reservoir was full before working on it so there’s no internal or external leak.

      I’m guessing I won’t be able to diagnose this, sounds like a job for a pro shop. I’m just wondering if it’s due to all the contaminants in the system destroying seals or if the master cylinder is bad.

    Viewing 10 replies - 1 through 10 (of 10 total)
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    • #581730
      Aaron AbajianAaron Abajian
      Participant

        Hello. Your problem could be one of the things you mentioned or several other issues. After reading your concerns, I reminded me of of one of the first repair jobs I ever did very early in my career as a mechanic. I was replacing both front calipers on a Ram pickup truck. Unfortunately, I got the left and right sides mixed up and switched them. Everything bolted up nicely and I proceeded to bleed the brakes. With the calipers on the wrong sides of the car, the bleeder valve ended up at the lower portion of the caliper and would let clear fluid out with no bubbles. This left a large pocket of air at the top of the caliper. I checked online for pictures of the calipers for your car and it looks to me from the bolt pattern, that it is possible to bolt them on either side. If the parts guy sent you the wrong side by mistake, this could be your issue. A quick glance could rule this out. If this is not the case, I would definitely check the master cylinder for leaks… Are you losing fluid anywhere? Good luck!

        #581765
        TexarkanaTexarkana
        Participant

          Yes, the front and rear calipers on this vehicle are interchangable on either side.

          As far as I can tell there are no leaks in the system, the bleeder valve is in the same place as the old caliper so it went on in the proper position.

          My best guess at this point is the master cylinder is bad, but I don’t have a scan tool to cycle the ABS system to completely remove all the old fluid out of the system.

          #581780
          college mancollege man
          Moderator

            Is this car 4 wheel disc or drum rear? If drum they must be adjusted
            correctly to firm the pedal. if disc does the pedal firm up with the
            pedal pumped and the car off? If the fluid condition was as bad as you
            say.I would suspect the master cylinder. Open a bleeder and pump the pedal
            does fluid shoot out?

            #581789
            TexarkanaTexarkana
            Participant

              Yes, 4 wheel anti-lock disc brakes. Pedal is firm and doesn’t sink when the engine is off. Bled the brakes until clean fluid and no air bubbles came out and it still has low pedal.

              #581793
              college mancollege man
              Moderator

                [quote=”Texarkana” post=88520]Yes, 4 wheel anti-lock disc brakes. Pedal is firm and doesn’t sink when the engine is off. Bled the brakes until clean fluid and no air bubbles came out and it still has low pedal.[/quote]

                The pads have good meat left?

                #581801
                TexarkanaTexarkana
                Participant

                  Thicker than a nickle so enough meat to pass inspection. If I had to guess about a 1/4 inch.

                  #581893
                  college mancollege man
                  Moderator

                    [quote=”Texarkana” post=88526]Thicker than a nickle so enough meat to pass inspection. If I had to guess about a 1/4 inch.[/quote]

                    That could be a factor for the soft pedal due to the pads being so worn.

                    #585708
                    TexarkanaTexarkana
                    Participant

                      Well I saw her about a week ago and she (my friend) said the pedal doesn’t feel any different than before I worked on it. My pads are low at the moment (about an 1/8 inch from the squealers) and my pedal isn’t dropping to the floor like her’s is so I’m pretty sure it’s the master cylinder.

                      #586029
                      EricTheCarGuy 1EricTheCarGuy
                      Keymaster

                        Mixing different types of brake fluids like that can be problematic. It can effect the entire system. That said, it may be a master cylinder problem as you suspect. You might try this first however.

                        Also more info here.

                        http://www.ericthecarguy.com/faq/solving-brake-problems

                        #586035
                        kylekyle
                        Participant

                          this car 4 wheel disc or drum rear?

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