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348 Brake issues

Discussion in 'Technical Q&A' started by 968cs_red, Mar 30, 2005.

  1. 968cs_red

    968cs_red Rookie

    Aug 27, 2004
    24
    UK
    Full Name:
    Matt H
    Hi - this is also posted on the model specific area,
    =======================================

    Hi there,

    I have a 348 and I've been having a few problems with the brakes. A couple of weeks back I fitted new front discs (grooved) and new stainless braided brake lines all round, new Mintex pads up front too. I then bled the brakes, replacing the fluid with ATE super blue stuff. After the new pads and discs bedded in there was a definite improvement in the braking from before... more bite and a firmer pedal. But the pedal then, over a period of a few drives and 100 miles or so started too feel slightly softer than before.. it felt like a small amount of air in the system.

    I re-bled all four calipers again (x2 bleed nipples) starting from the one furthest from the master cylinder and working my way to the nearest. I did this, as before, using a pressure bleeder (the type you connect to a spare tyre set to 20 psi max.). All seemed to go well and no air bubbles seemed to be present. I ran another ~500-750 ml through. I used around 1 litre the first time.

    Again, after doing this the pedal felt nice and firm and as I would expect with the goodridge lines and new fluid... however after a couple of hundred miles over a week... the pedal now feels noticeably softer again!

    The only thing I noticed during my work which concerned me was when I disconnected the pressure bleeding line from the reservoir after finishing the bleeding, a lot of brake fluid from the reservoir on the car seemed to get sucked back into the bleeder reservoir quite quickly and looked like it was quite airated ? Can't remember if this happens usually when I have used this bit of kit on other cars.

    One other thing was after bleeding, with the brake fluid reservoir cap on etc, I tried the brake pedal... nice and firm... but pressing the pedal didn't seem to apply enough force to the rears (I had car on axle stands)... I turned the ignition on and repeat the pedal press... this time the rears calipers were being activated properly. I guess this has something to do with the servo but I'm not properly clued up on this system yet.. ? Should I bleed with the ignition on?

    Would really appreciate any thoughts or suggestions or possible causes of the pedal going a bit soft.

    My next plan at the moment is to bleed again without the pressure bleeder using the traditional pedal pressing method.

    cheers, thanks in advance!
    Matt
     
  2. Ken

    Ken F1 World Champ

    Oct 19, 2001
    16,078
    Arlington Heights IL
    Full Name:
    Kenneth
    From your discription, it seems you're introducing air in the system. This is typical of either a master cylinder or servo failure. If you are losing fluid I'd suspect the servo. Keep in mind I have a Lotus, not a Ferrari so your mileage may vary! I had a bad servo that sucked all my fluid out over time; when I refilled it and bled the lines I managed to turn a seal on the MC. Like you, it would be a good pedal for a few days and then deteriorate.

    Ken
     
  3. 968cs_red

    968cs_red Rookie

    Aug 27, 2004
    24
    UK
    Full Name:
    Matt H
    Thanks for the reply Ken, I'll have a look into it.

    I heard yesterday from someone that the system on the 355 is 'self bleeding' and all is needed is to have the ignition turned on and the system is pressurised - then all that is needed is to bleed from the calipers as normal with no brake pedal pumping etc required ... he thought it may be the same on the 348 - can anyone comment on this?

    thanks,
    Matt.
     
  4. ernie

    ernie Two Time F1 World Champ
    Owner Lifetime Rossa

    Nov 19, 2001
    21,869
    The Brickyard
    Full Name:
    The Bad Guy
    As far as I know you have to bleed the breaks on a 348. The breaks will self adjust, but i haven't heard of "self bleeding". Try bleeding your breaks the two man method, just as you said. Now if that doesn't work, I would check the connection of the new lines for any signs of leakage. If you don't find anything leaking, and all the air is out of the lines, then the only conclusion is that either the MC or the servo is bad. So make a very close inspection through out the system for leaks.
     
  5. Ken

    Ken F1 World Champ

    Oct 19, 2001
    16,078
    Arlington Heights IL
    Full Name:
    Kenneth
     
  6. maserati424

    maserati424 Rookie

    Apr 11, 2004
    29
    Berlin, Germany
    Full Name:
    frank gablenz
    ATE Mark 2 ABS systems are"" self bleeding",because there is a highpressure pump for the system.
    With ignition on you can bleed the system with the pressure of the pump.
    You should not let the pump run to long,an let it run out of fluid.
    The system is also the brakeservo.
    Mondial t and 355 haveit ,and as far as i know the 348.
     
  7. ernie

    ernie Two Time F1 World Champ
    Owner Lifetime Rossa

    Nov 19, 2001
    21,869
    The Brickyard
    Full Name:
    The Bad Guy
    Well blow me down! You learn something new every day. So what is the technique for bleeding the breaks using the system pump?
     
  8. fatbillybob

    fatbillybob F1 World Champ
    Owner Consultant

    Aug 10, 2002
    16,945
    socal
    Not true on the self bleed. There is no such thing. The FBB method reported here many times is the only way to reliably get a hard pedal with a 348. I have tried all the other methods they all work just not as well. I proved this to myself on the racetrack not the street and I theashold brake and trail brake so I beat them up good. YMMV so try it yourself. Also, speed bleeders on 348s suck been there done that or perhaps I'm an idiot. Running pump with out bleeding at the screws only presurrizes the system. The air is still in there. The pump will self-bleed but not the rest of the system.

    here is the method:
    1) key on so so pump can run. Becareful this does not mean engine on which may need to be done on some cars. This is the most critical thing to do with any ABS system. You can bleed without the pump but the pressure helps you get a rock solid pedal and it purges crappy fluid out of the pump valves. That saves you money in the long run.
    2) two man bleed at claiper farthest from reservior first
    3) if and when pump starts to run shut off bleed screw at caliper and only bleed again when the pump stops
    4) repeat for all coners then bled your clutch if you want
    5) make sure to top off reservior as needed
    6) note the clutch inlet is higer on the reservior so watch this before you bleed the clutch. Dumb design? Maybe not. If you leak fluid you loose the clutch before you loose the brakes. I'll take that trade off
    7) when changing total fluid with starting from a dry master cylinder just suck out the old say ate glod and put in the ate blue. Then bleed until you get blue out the screws and you are done. pumping our all the fluid then pouring new fluid in means you have huge air in the ssytem and need to prime the master before you can effectively get all the air out even with a high pressure system like the abs.
    8) if you start from a totally dry master then prime your master on the bench before you install it. Then add fluid to the reservior and bleed it.
    9) IMO it is just better to bleed brakes and change fluid reguarly and that prevents so much crap from building that you have to do a whole flush to dry system clean out.
     
  9. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    25,515
    Austin TX
    Full Name:
    Brian Crall
    If you have self bleeding ABS you better tell Bosch and ATE, they've never heard of it.
     
  10. ernie

    ernie Two Time F1 World Champ
    Owner Lifetime Rossa

    Nov 19, 2001
    21,869
    The Brickyard
    Full Name:
    The Bad Guy
    Okay good, for a second there I though I was going crazy. LOL
     
  11. 968cs_red

    968cs_red Rookie

    Aug 27, 2004
    24
    UK
    Full Name:
    Matt H
    Thanks for the replies, chaps.

    Pretty sure I'm not losing any fluid - well not from anywhere that I have checked so far. I've inspected all the joins at the new brake lines, at the caliper and the joins to the hard lines. Also checked all the caliper bleed screws and all are dry with no sign of leakage.
    Don't appear to be losing any fluid, the level in the reservoir has not gone down.

    My theory is its something to do with the brake fluid rushing back into the pressure bleeder reservoir when I disconnect from the spare tyre.... also the fact that I didn't realise its best to have the ignition on when bleeding won't have helped.

    I'll try again with ignition on, without using the pressure bleeder and see how it goes!

    cheers :)
    Matt.
     
  12. maserati424

    maserati424 Rookie

    Apr 11, 2004
    29
    Berlin, Germany
    Full Name:
    frank gablenz
    Sorry was my mistake.
    You can use the pressure of the system, you must open every screw at the calipers to let the air out of the system.
    Selfbleedind means only you don´t need a second person to push the break pedal or using a speedbleeder.
     

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