Master Brake Cylinder

[Kitten]

Hi All,

I think my beloved Golf GT TDI has become jealous that I got a work car for a month. I left her on the driveway for 10 days, come back and the brakes felt awful!

When I pressed the pedal the car, the pedal moved up and down under my foot when I was braking lightly, so I had my friend come over and have a look. After a couple of emergency brakes the juddering stopped, but then started again but only when I really pressed the pedal.

My friend showed me that if it was air in the system you could pump the pedal and then it would become hard, however with my car after you have pumped the pedal, if you rest your foot on it the pedal sinks to the floor, and my friend has deduced that the master brake cylinder has gone. My lovely little car has done over 180k mileage so I'm a bit worried about what else may start to go wrong now?

Has anyone had their master brake cylinder changed and if so can you give me a rough ball park figure of how much I am looking at? And does it sound like the master cylinder?

Thanks,
Ali

[boldybutch21]

im guna watch this as ive just fitted a new rear brake caliper and now have weird brakes and sinks if you hold your foot on the brakes got all air out of the system aswell so i think we both need master cylinders....

[kenney]

Hi kitten This is an extraordinary thing which happens on most diesel,vehicles without anything being wrong.I remember the first time i experianced it,replaced the master cyl,replaced each caliper,one after the other,only to find it was just the same,i.e with the engine running and your foot on the brake the pedal,will floor.I was a bit wiser when i tried the same thing on other vehicles,when i found out they were the same.How ever if the pedal floors without the engine running,then there is something wrong.Regarding the pedal juddering,i think maybe one of the discs could be warped

[Crasher]

Be aware that changing the master cylinder on a Golf 4 means having to bleed the brakes in basic settings using a diagnostic computer, two people, a battery charger and preferably a pressure brake bleed unit. It is a real pain on ABS Mk20 systems with ASR or ESP as you must follow a 17 step process dictated to you on screen, if the process is not carried out correctly, the ABS light comes on and you cannot delete the fault code. Non ASP/ESP Mk20 and Mk60 systems are slightly less tedious.

[Kitten]

Thanks for that wonderful information Crasher! :P I am sincerely praying it isn't.

As I said it is my friend's diagnosis so I've got it booked in to see the mechanic on Monday so I'll let you know what he says. Here's hoping boldybutch it's good news!