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General => The garage => Topic started by: stew8vmk2golf on 21 August 2003, 11:20

Title: brake servo.
Post by: stew8vmk2golf on 21 August 2003, 11:20

hi there i have swapped the engines over in my car, and i also swapped all of the braking over, I had to lengthen the rod that comes out of the brake servo, and attaches to the pedal. Anyway now the unit is all back in my car when i press the brake pedal i get a loud hiss from inside the car. Have I buggered a seal and is it easy to repair or shoould i get a new servo? (how much) Finally if i need a new servo would one from a mk3 fit as the local scrappy has one? My car is a 1989 mk2 8v golf gti.

Title: Re:brake servo.
Post by: stew8vmk2golf on 22 August 2003, 16:56

it seems that there is nothing leaking just the white plastic tube rubbing on the rubber. The only proble is that my brakes are really spongy when the engine is running, i've bled the brakes and its still happening, any ideas?

Title: Re:brake servo.
Post by: mk1 on 22 August 2003, 20:09

Sounds like the servo is leaking vacuum when the brakes are pressed, does the engine run different when it does this ?. Cant comment on the mk2 - mk3 compatability, any one?.
Spongy brakes sound like there is still air in the system, bleed the brakes again, pay attention to the rear callipers, Steve.

Title: Re:brake servo.
Post by: stew8vmk2golf on 22 August 2003, 23:42

no the engine runs exactly the same when the brakes are pressed, that is what is so confusing. I've bought a second hand servo from a scrappy and still having the same problem.

Title: Re:brake servo.
Post by: richandhazel on 23 August 2003, 11:40

When you bleed the brakes are you making sure the rear brake bias valve on the rear subframe is fully open? Just a thought  ???.............

Title: Re:brake servo.
Post by: stew8vmk2golf on 23 August 2003, 16:21

oh s  :-X :-Xt, I completly forgot about that bit. Dont i have to pul the leaver totally towards the rear axel???

Title: Re:brake servo.
Post by: richandhazel on 23 August 2003, 16:53

Can't remember which way, but it's which ever way it would go if you loaded up the rear of the car and made it heavier.

Title: Re:brake servo.
Post by: golfvr6 on 23 August 2003, 16:57

Jack the rear of the car up HIGH, leave on axle stands overnight. The air bubbles should then settle up at the rear axle as long as you have jacked it high enough. Bleed the rears with the the rear regulator clamped. This should get rid of any annoying air bubbles stuck in the system.

Title: Re:brake servo.
Post by: richandhazel on 23 August 2003, 16:59

Just cut this out of the service manual:-

On models equipped with the load-sensing pressure regulator, the actuator lever must be held toward the axle beam (toward the rear of the car) when bleeding the rear brakes to allow maximum fluid flow


..........so you're right, towards the rear axle.

Title: Re:brake servo.
Post by: richandhazel on 23 August 2003, 17:02

I'm sure you are well aware of the correct sequence, but in just in case, this may help too:-


For the best possible results, bleeding by any method should start at the wheel farthest from the master cylinder and end at the wheel closest to the master cylinder. Thus, the correct bleeding sequence is as follows:

1. Right (passenger-side) rear
2. Left rear
3. Right front
4. Left front

Good luck.

Title: Re:brake servo.
Post by: golfvr6 on 23 August 2003, 17:02

Depends on model as i have seen some different ones. I think as a general rule if you clamp the thing so it is compressed then that will do the job. Works on mine anyway!

Title: Re:brake servo.
Post by: stew8vmk2golf on 23 August 2003, 17:17

thanks for the advice, i will wait till my g/f gets home and get her pressing the pedal, should see her moaning about a sore leg for the next two weeks.  ;)