Servo - working or not

[hansaxl]

Hi everyone,

my S4/Sprint still has the servo fitted. However, I doubt that it works, as the pedal force is quite high, even with soft compound brake pads, and there is no feel whatsoever of the servo "coming in", which had been bery pronounced on the Plus 2 I drove before.

So, is it possible at all to have a dysfunctional servo and at the same time brakes that perform as if there was no servo at all?

I think I could test this by disconnecting and plugging the vaccum hose, correct?

If it does not work, I will probably get rid of it. On the other hand, here we have a typical case where originality and layiness form a very nice combination, don't you agree?

Thanks for your comments,

Cheers,

Hans

[Quart Meg Miles]

Yes, yes & yes. What were the questions?

My S130 servo filled with fluid and the brakes were simply heavier but perfectly driveable so the lighter S4 should be fine without it. In fact, because the car was so over-servoed (at about 3:1) and the clutch so heavy I seriously considered moving the servo to the clutch. The vacuum is the power source for the servo so disconnecting it eliminates any servo action. I don't recall a servo delay on my car and I was still driving the S2 at the time.

Originality is in the eye of the beholder! As yours already isn't, just messing about with the brake servo shouldn't offend too many people but you can leave the defunct unit in place, complete with pipes, to create the illusion of originality.

[oldelanman]

Hi Hans,
There is a whole page in the Workshop Manual on how to test the brake servo and diagnose faults. If you don't have a manual let me know and I will see if I can scan the page and post it here.

[hansaxl]

Thanks for your answers.

Well then, looks like a nice half day messing about with the brakes. Thanks for offering to scan the workshop manual, but this is not necessary. I got one, just did not think about it, as usual.

Cheers,

Hans

[UAB807F]

Hi Hans,

The way I used to test mine before the annual MoT was to press the brake pedal several times without the engine running to remove any residual vacuum and get a hard pedal. Then start the engine whilst holding the pedal firmly down and you'd feel a slight give in the pedal if the servo was working. That's the way the garage checks them, or at least how they used to do it.

Brian