Post Number: 36
|Posted on Wednesday, 10 June, 2009 - 15:32:
Wondering if anyone could assist with a braking issue?
My Cloud II - dual master cyl - does not appear to be getting it's full servo assistance when doing long braking actions. What I mean by this is for example if I am braking quite a distance back from the traffic lights, the brakes at first feel normal. Then half way through the braking (my foot has not come off the pedal) the pedal suddenly feels very hard and the car is not getting the same braking power.
The servo has a new lining, is correctly adjusted and the master cylinders were serviced last year.
I'm thinking the following could be possible - would anyone agree?
- There may be air in the system?
- Some kind of failure in a master cylinder?
- The pistons in the master cylinders need to be adjusted (their length)?
Would very much appreciate any suggestions you may have!
Post Number: 1123
|Posted on Wednesday, 10 June, 2009 - 16:52:
Jeff/ Assuming the systems have been properly bled - the detail is all in the librrary, my money is on a failed master cylinder(s). There is an impression among worshippers that having two master cylinders gives two separate braking systems. This is not so. As you know the two are activated by a toggle which by design apportions the braking efforts appropriately between the front and rear wheels. When one fails that piston goes to the bottom of its stroke and the other just sits there.
When you apply the brakes the first pressure is the rear brakes being applied manually. The servo then winds up and drags the master cylinder trapeze and the pistons into their cylinders and all is right with the world. As one or both of the cylinders leaks its fluid past the pressure seals and back to the reservoir, the servo continues to push until there is nothing left to push and the front brakes and rear brakes come off and all you are left with is the equivalent of pulling the hand brake on!
I note you have had the cylinders overhauled. They should have been sleeved with stainless steel. If that was done they may not have sleeved the bridge piece at the front of the cylinder. If this is not done the piston can wiggle somehow and release pressure even with new seals.
The best way to test for this problem, is to stop the car on a steep slope and hold it firmly with the foot brake. If the master cylinders are leaking you will find that after amoment or so the car will start to move despite the application of the pedal. Re-application usually gives instant brakes again.
Dr. Omar M. Shams
Post Number: 25
|Posted on Thursday, 11 June, 2009 - 02:57:
in the old days when I had an S3 I remeber having the same symptoms as Jeff and Bill's assessment is spot on.
Also, my problem was compounded by having the wrong hoses fitted that had constricted considerably on the inside (a la colesterol). I had to replace all the hoses on that car. Good luck Jeff.
Post Number: 37
|Posted on Thursday, 11 June, 2009 - 14:32:
Thank you very much Bill and Omar. I will check this out the next time I drive the car.
Many thanks! Jeff