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Thread: Brake Misery

  1. #1
    Join Date
    Apr 2007
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    Perth WA
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    Brake Misery

    Hi All - thanks for all the valuable info guys :-)

    My Vacuum pump blew in the old 95 300TDi (non ABS) about 4 months ago. Brakes still worked if you pushed hard, so I drove it while waiting for the vacuum pump to arrive.

    Installed new Vacuum pump, Servo was hissing when brakes pressed but no power brakes, still required hard push to stop.

    new Servo, backed the adjuster nut on the servo 1.5 turns in making the rod shorter. Brakes work really well when you first start , lots of power assist boost, then after 10 to 15 minutes driving the brakes don't ease off after braking, and the car needs more and more power to maintain speed - down to 3rd gear on flat ground barely able to get 65km/h.

    If I stop the motor and pump the brakes it all seems to reset for a few minutes and stops dragging. When I stop all of the wheel rims are very hot and theres a lot of brake smell.

    I can stop at the lights with a steep uphill grade and the car does not roll back without hand brakes or foot brake pressure. If I disconnect the vacuum hose the brakes issue does not continue, and the car is back to being nippy and rolls down hill, but also I don't have power assist.

    Can anyone suggest a fix please, this is driving me even nuttier than usual.
    Last edited by lenleggo; 9th November 2014 at 11:08 PM. Reason: adding

  2. #2
    Join Date
    May 2009
    Location
    Tatura, Vic
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    A lot of cars have an adjustable push rod coming from the booster into the master cyl. Make sure it is not over adjusted.
    Dave.

    I was asked " Is it ignorance or apathy?" I replied "I don't know and I don't care."


    1983 RR gone (wish I kept it)
    1996 TDI ES.
    2003 TD5 HSE
    1987 Isuzu County

  3. #3
    Join Date
    Oct 2006
    Location
    canberra
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    Push rod adjustment or faulty booster

  4. #4
    Join Date
    Apr 2007
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    Push Rod adjustment

    Ok, I have the answer on this;

    Turns out it was my error....

    The Servo comes with a preset push rod in place, I thought it was preset to the correct length,,, its not. When you install you should check how far the old servo push rod is from the face plate, then set the new push rod to the same setting as a start, then check and adjust as required.

    The big trick to all of this is that the push rod inside the servo unit has a 7mm brass nut on the end of a threaded rod which screws into the body of the push rod. The entire push rod turns if you put a socket spanner on it, and there is no adjustment of the push rod length.

    I was able to show that by putting a small 150mm metal ruler inside with a small piece of metal held across the servo face giving a very accurate depth reading. The new servo came with a push rod depth setting from the face of 21mm, the old one was set at 24mm. All my previous attempts at adjustment had not changed the depth at all.

    To adjust get a pair of long nose pliers and firmly grasp the base of the push rod below the thread, then insert a 7mm socket and wind it clockwise, 2 full turns got it down to 24mm and I took it another half a turn to make sure, now 25mm.

    The brakes dont come on until I depress the pedal 30mm, they then perform very well with extremely sharp braking that is superior to my Hyundai i30 business car with all round discs. The steadily increasing brake pressure without me touching the pedal is gone, the power is back and the car does not smell like hot brakes when I stop. Also the car will roll down hill happily at any time.

    At some point when I can be bothered, I will probably remove the Master Cylinder again and wind the push rod back to say 24mm so that it starts the braking at 15mm brake depression, but for now I'm just stoked the old girl is working properly again and the brakes are good.

    Thanks to all for the help and advise on this, and I hope this helps someone else to avoid the misery my lack of knowledge subjected me to.

    I will try and post some pics on this as well

    Many thanks to the guys at ROVERCRAFT Bayswater for all their patience and help.
    Attached Images Attached Images

  5. #5
    Join Date
    May 2009
    Location
    Tatura, Vic
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    In another life I worked as a brake specialist. All we used to do was offer the master cyl to the booster and then feel for any pressure against the master cyl spring.

    We would then when necessary adjust the booster push rod to give about .25 to .5 mm clearance.

    All you need is clearance, the less the better to maintain a good pedal.
    Dave.

    I was asked " Is it ignorance or apathy?" I replied "I don't know and I don't care."


    1983 RR gone (wish I kept it)
    1996 TDI ES.
    2003 TD5 HSE
    1987 Isuzu County

  6. #6
    Join Date
    Oct 2006
    Location
    canberra
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    I fit boosters and m/c on a daily basis I haven't had one yet that I have had to adjust from factory except dodgy eBay generic booster and master cyl combos for Disc brake conversons on chevs so I find it a bit odd. But I have had to make and adapt push rods in boosters to suit different applications and changing bolt patterns to suit different masters. I have a basic tool I use to measure and set pushrod adjustment ile take some pics when I get a chance not hard to make one at home. It could come in handy for some one. One day.

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