Help Needed With Mk 3 Golf TD 1994 Braking System - Master Cylinder

[tsam19]

In connection with an earlier thread as listed below:

http://www.vwaudiforum.co.uk/forum/s...ad.php?t=76118

I want to know if its possible to 'bleed the master cylinder' on a Mk 3 golf td
or bleed anything else to get the brakes to work as stated in my above thread, the brakes are non existent & the pedals really sloppy even after a lot of work carried out.

As Ive heard some master cylinders can be bled.


No ABS - front discs - rear drum only.

Just wondered if there was anything else to bleed?

Whats in the vacuum pump body ,is it brake fluid or oil ,does that need purging?

When I replaced the cover it was only half full of fluid.


When the engine is on the brake pedal is sloppy, but gets a temporarily firmer when you pump the pedal fast a few times, but firmness disappears again when pedal fully pressed in.

Not sure what could be causing it ?

The valve in the vacuum pump cover works properly now as this was replaced.
The pipe from the servo to the vacuum pump was changed due to a split.
The master cylinder was changed - not the servo.

Brake fluid is getting to all the bleed valves as noted when bleeding the system.

A lot of air came out of the front right valve both on the up & down stroke of the pedal, but then stopped eventually.

Pedal was firm after bleeding the system, its only when engine was turned on that the above occurred.

Does it matter how fast you pump the pedal when purging the system, if so what effect will it have on the system after.

Also are you meant to lock off the bleed valve with the pedal in the midway position ?


I noticed that the servo serial number from the donor car was slightly different at the end to the one thats on my car, probably because it was a newer model by a couple of years, but the servo design was basically the same & so was the vacuum pump cover design & fit.

I changed the vacuum pump cover as the one way valve in mine was not as it should be, air would go in both ways instead of just one way.

New brake bleed valves all round too.

I bled the brakes from rear right,rear left,front right then front left just as the manual states & the pedal man stated the pedal was getting firmer all the time.

The engine was off whilst doing this.

The brake reservoir had the correct amount of brake fluid in all the time during the process.

All the air was removed from the system.

With the engine off the pedal did seem as it should be, firmer to the touch with your foot.

However upon starting the engine & testing the brakes there was nothing, foot to the floor again ???

No brakes again !!

Can anyone help ?

Have I missed something out ??

Could these symptoms be a faulty SERVO itself ????

[Golf Loon]

Have you got a vacuum leak between the servo and the engine?

Check the hard plastic line and the non return valve and flimsy plastic vacuum connectors.

can you hear a hiss when you push the pedal??

[tsam19]

I replaced that pipe that connects the servo to the vacuum pump.

As it was split at the servo end & there was a hiss when I got out of the car after driving.

I replaced the vacuum pump cover as the valve in that was letting in air both ways.

I tried a different way to bleed the brakes, which seems to have improved the braking.

Open bleed valve as pedal is pushed to the floor, then lock it off.
Let pedal rise & follow the above procedure again a few times.

I think the problem was the way I originally bled the brakes.

Also someone suggested that the back shoes could cause the sloppy pedal too especially if they weren't set correctly when fitted in 2006.

All in all the brakes seem to work now, so I'm happy with that.

Thanks for replying back.