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Brake bleeding issue

Discussion in '308/328' started by gt500blue, Mar 31, 2020.

  1. gt500blue

    gt500blue Formula 3
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    Oct 18, 2006
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    Hi all,
    I had my brake booster rebuilt (by power brake booster exchange - the did a fantastic job from the rebuild to finish and even steamed off the original label and returned it at a VERY reasonable price). The booster seems to work fine.

    Problem is that my master cyl sat in a ziplock back for over a year before I did some other work and found the time to put it in this weekend. Now all seems to work well with the booster. However, I cannot get the front two calipers to bleed. They only dribble fluid (clean fluid coming out).

    I tried with my motive pressure bleeder which I have used multiple times with no issue in the past. Rear calipers bled fine. Pedal still sinks to the floor as if there is air in the lines. Yet I do get braking pressure on the disc when applying the brakes, but only when I depress the pedal completely. But the pedal does not get stiff from pumping (leads me to believe I have a ton of air in the line still).

    I'm wondering if my master cyl is gone from sitting so long or if I have a problem with the differential pressure switch. Since taking the master cyl off is a PITA, I thought I would ask for opinions before I do that. I also hear that the differential switch is no fun to get to as well. :(

    I probably should have made the effort to rebuild the master cyl since I had it off the car for so long.

    Thoughts?
    Thank you!
    GT
     
  2. ferrariowner

    ferrariowner Formula Junior

    Feb 21, 2014
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    Mansfield, TX
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    Ron
    I would try dissembling the master cylinder and see if there are any pits. As I recall you can get a rebuild kit from Superformance for around $20. If the master is pitted, you will need to replace it or get it sleeved (Whitepost). Good luck.
     
  3. johnk...

    johnk... F1 Veteran
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    Jun 11, 2004
    7,905
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    Did you prefill the master cylinder?
     
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  4. gt500blue

    gt500blue Formula 3
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    I did not. I had the reservoir off to assemble the booster and master cyl. The back screws are difficult to get to with it on the master. I cleaned the master with brake clean and put the reservoir back on and filled it. Thought the pressure bleeder would fill it once I opened the bleed valves on the calipers. It worked fine for the rear brakes. Front brakes dribble. Why would the brake fluid travel to the rear circuit, but not the front? Maybe I should pull the reservoir off and try to prime it.

    Thanks!
     
  5. gt500blue

    gt500blue Formula 3
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    Yes, thank you. I'm trying to avoid taking it off first, as it's a PITA to unbolt it from the booster. But if all else fails with trying to bleed it, I'll have to do that.

    I'm pretty sure if there is air in the line, the brake pedal will just be mush and travel all the way to the floor. That is what it's doing, so I'm assuming it's air in the line. I suppose if there are pits it could have ripped the seals on the piston and fluid is not compressing for the front circuit. I may end up tearing it down unfortunately.
     
  6. thorn

    thorn F1 Rookie
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    Aug 7, 2012
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    Did you bench bleed the master cylinder?
     
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  7. gt500blue

    gt500blue Formula 3
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    No.. I thought it would bleed both circuits with the pressure bleeder. Maybe I should have done that.. Would have been good sense. So it is possible that I still have air in the MC for the front circuit? Since I was getting fluid dripping out of the front calipers, I thought the MC was full. But maybe there is still air in the MC.

    I suppose I can do this with it installed and put a pan and tons of towels under the port (disconnect the brake line) and pump the brake pedal slowly to see if I get fluid coming out. Make sense?
     
  8. gt500blue

    gt500blue Formula 3
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    I could then put in some MC plastic plugs and see if the pedal gets firm. If not, then I know I have a MC seal issue. If firm, probably good to try and bleed the lines agian.
     
  9. fatbillybob

    fatbillybob F1 World Champ
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    Aug 10, 2002
    18,212
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    Bleed master. disconnect outflow at the MC run a line from outlfow back into the MC reservoir and pump it to bleed the master. Then reconnect and bleed brakes. Consider not going full stroke on an old master. It is possible going full stroke on not great maintained mc scratches the seals to wall interface and then ruins the seal. Then only recourse is new or rebuilt MC.
     
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  10. gt500blue

    gt500blue Formula 3
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    Yes, thank you! I read that previously. Probably too late as the pedal was pushed to the floor several times while my son was trying to help me bleed the front when the pressure bleeder didn't seem to work. I didn't want to pump the pressure beyond 5 to 7 PSI. So the pedal was pushed to the floor. We'll see, damage may already be done and may have to rebuild if the piston/plunger is not too pitted. I'll report back.

    Thanks to all for your help. I didn't do the procedure right, so time to pay the piper I guess.

    Much appreciated!
     
  11. fatbillybob

    fatbillybob F1 World Champ
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    We all learn. Still cheaper than taking it to Ferrari mechanic and you learned a lot. I look at automechanics as part of the hobby.
     
  12. waymar

    waymar Formula Junior

    Sep 2, 2008
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    Wayne
    I had my MC rebuilt and sleeved by a ‘reputable’ supplier. Could not get any pressure..... turned out the supplier put the wrong seals in the rebuild. I swapped them out with a SF kit and bingo..... no more issues...... just saying....
     
  13. gt500blue

    gt500blue Formula 3
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    SF Kit? I'm looking for a rebuild kit now. What is the SF kit? Thank you!
     
  14. gt500blue

    gt500blue Formula 3
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    Well.. thanks. I have pulled this engine out of this car, do my timing belts, rebuilt all the fuel lines, electrical, clutch, final drive seals, radiator R&I, distributor, plugs, wires, replaced fuel injectors, Warm up regulator, window motors (no fun), Suspension bushings, etc. Just finished an engine rebuild for my son's Nissan 350z with JWT cams, H-beam rods, Carillo pistons, etc. Love working on my cars. But this is really embarrassing :) LOL!
     
  15. dinonz308

    dinonz308 Formula Junior
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    Wish I had the skill and confidence to do those things. Right now I'm scared to pull out my dash panel to ground the volt meter. Feel a bit intimidated by my cars.
     
  16. dwhite

    dwhite F1 Rookie

    I had a problem last week with my rear brakes. They were not working after a fluid change and rebleed. Loosened line at master to see if there was pressure, unfortunately not much.

    Had the master rebuilt in 2013 and it was resleeved. Back then I removed the master with the reservoir, what a pain. This time after reading years ago to pull the resv. first, that is what I did and it was out in 20 mins tops including sucking out as much fluid first and pushing the front out with the pedal as it is the side which fills from the top crossover from the back tank.

    Lucily brought it to the place, Apple Hydraulics, who originally rebuit it and they pulled it apart and replaced all the seals as I waited about 15 mins.

    Used the motive power bleeder to bleed system and had no problems. Brakes work great.

    Good luck.
     
  17. fatbillybob

    fatbillybob F1 World Champ
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    We have all been there and revisit there regularly.
     
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  18. 2NA

    2NA F1 World Champ
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    Dec 29, 2006
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    5-7 psi is probably not enough. I typically pump my Motive bleeder to 15 psi. Try that first.
     
  19. johnk...

    johnk... F1 Veteran
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    Jun 11, 2004
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    Porsche recommends 2 bar, so 30 psi.
     
  20. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    Dangerous on a lot of masters with a reservior held in place by rubber bushings. I have seen many get blown off the car.
     
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  21. gt500blue

    gt500blue Formula 3
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    THanks... last time I did it I went to 15psi on the gauge and I was leaking at the seal around the tank nipple that enters the top of the MC. I did remove the tank the other day and checked the seals. Looked fine, so I was a bit hesitant to go higher. I may try that first before pulling it out to see if I can get it bleed. We'll see tonight.
     
  22. waymar

    waymar Formula Junior

    Sep 2, 2008
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    IMHO.... if ‘bench bleeding’ does not work, check internal master seals, mine were wrong from the rebuilder, simple job. I have had great success over 15 years with my 308GTSi by gravity bleeding the system each Springtime.
     
  23. gt500blue

    gt500blue Formula 3
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    Understood... thank you. I'm already searching on a good rebuild kit. If you have any ideas as to brand and distributor, I can rebuild it.
     
  24. fatbillybob

    fatbillybob F1 World Champ
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    Aug 10, 2002
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    It is incredibly difficult to find consistent reliability in the rebuilding space especially because everything today is so throw away get a new one.
     

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