Mystery brake problem - servo?

[orpheusvw]

Hi,

I have a problem with my '71 vans brakes and hoping someone more knowledgable than me can help me out, I've searched the forum but can't find anything relating to the same fault.

My problem occurred today when I went to reverse the van from the garage after a few months of not moving, after a few feet the brakes appeared to seize up and stop the van, no matter how many rev's the van wouldn't move, the brake pedal was rock hard. When I turned off the engine the brake pedal appeared to soften and the van could be pushed freely! When I started the engine the same thing occurred the brake pedal went hard and the van wouldn't move, I disconnected the vacuum pipe in the engine bay and the van drove normally but with harder to work brakes than normal (as to be expected with no vacuum pipe attached)

When I first got the van I replaced most of the brakes with the servo being a new German Ate one at great expense!!

I'm stumped as to what is happening and hoping someone has an easy answer, clearly the fault appears to be servo related but I thought when they failed your brakes got harder to work, I can't seem to figure out why it's firmly applying the brakes?

Thanks in advance, and sorry for the long post...

 

[Trikky2]

Sounds like your right, its the servo.

First thing to check is that the brake pedal is returning fully. There's a spring that should pull it back. If its sticking then the servo will operate.

If your sure the pedal is returning fully to its stop (check by pulling the pedal back) then next you have to check there is free play (see the manual).

If that checks out as correct then its time to examine the servo itself. A faulty seal/valve or dirt on the seal's seating can cause this fault.

 

[orpheusvw]

Hi thanks for your reply regarding my servo, things been hectic with work so not been online for a bit,

I've managed to check the pedal last night and it all seems to be setup correctly, so I think ill strip down the front of the servo to see if I can see a problem, the Bentley manual mentions replacing the seals every time it's touched, looked in the usual places and can't see a repair kit??

After further investigations I've realised that the servo vents into the front arch, which is where I've been poking out some rust at the bottom of the 'B' post where it meets the cargo floor ready for welding up, will this hole being there cause a problem or is it likely some rust been sucked into my servo and knackered it?...


Cheers

 

[Trikky2]

Hi thanks for your reply regarding my servo, things been hectic with work so not been online for a bit,

I've managed to check the pedal last night and it all seems to be setup correctly, so I think ill strip down the front of the servo to see if I can see a problem, the Bentley manual mentions replacing the seals every time it's touched, looked in the usual places and can't see a repair kit??

After further investigations I've realised that the servo vents into the front arch, which is where I've been poking out some rust at the bottom of the 'B' post where it meets the cargo floor ready for welding up, will this hole being there cause a problem or is it likely some rust been sucked into my servo and knackered it?...


Cheers

You may be onto something there. If there is no filter on the end of the inlet pipe in the wheel arch then it is indeed possible that the rust you disturbed may have got inside.

If a flake of rust is causing the problem then removing the entire unit from the vehicle may enable you to get it out once its on the workbench.

 

[orpheusvw]

Thanks for your advice,

I'll start at the wheel arch end and work towards the servo, hopefully I can clean it up using an airline and giving the seals a good clean, can't afford to be buying another new servo!!

Cheers,

Paul

 

[gvee]

You may be onto something there. If there is no filter on the end of the inlet pipe in the wheel arch then it is indeed possible that the rust you disturbed may have got inside.

There should be a filter on that pipe, eh?
That I did not know. Will have to see if I can source something for mine.

 

[gvee]

You may be onto something there. If there is no filter on the end of the inlet pipe in the wheel arch then it is indeed possible that the rust you disturbed may have got inside.

There should be a filter on that pipe, eh?
That I did not know. Will have to see if I can source something for mine.