MGB Register Forum

Last year I fitted a reconditioned v8 servo to my 76 1.8 roadster.

Since then when I press the brake pedal until the brakes start to bite then hold the pedal steady the brakes firm up and it's as if I am pressing the brake pedal. If I lift off and re apply the brakes the pedal goes much further down and they are not as effective, as if servo isn't working.

Any thoughts as to why this is happening?

Evening Gordon.
Presume you have a remote servo. Servos have a different "assistance ratio" depending on what car they are designed for and it may simply be that the V8 one is not suitable for the 1.8 braking system.
Just a thought.
. Vic Butler

Sure it is not air in the system somewhere ?
I am having this issue at the moment, following the move of my servo from where somebody put it on the o/s inner wing to the normal remote servo position on the n/s scuttle ledge.
It was perfect before the change, so in my case, it can only be air. A number of attempts at bleeding seems to be improving matters...just doing it at present actually !
Paul.

Hi Gordon
The fitting of the servo needs careful attention to a few criteria, so make sure you have followed these. All the info you need is in here:
http://www.lotuselan.net/forums/downloa ... hp?id=5904 (thanks to the Lotus Elan website)

The angles and the positioning of the Air Valve reduce the amount of air that can be trapped in the servo when you bleed the system, so pay particular attention to these. As the angle of the servo increases it can be lowered on the mounting plate, but re-drilling the holes will be needed.
If you have to take the servo off the car, give it a shake and listen for fluid inside the 'drum' part of the servo. There shouldn't be any! If there is it is a sign the seals in the slave cylinder of the servo have failed.

It is worth pointing out that fitting a servo does not make the brakes better. This is dictated by the pads, discs, drums and brake shoes. It does reduce the effort needed to push the brake pedal down to achieve a level of braking. As the MGB and MGB V8 have essentially the same braking system, then the servo will be the same (Part No GSM125 is listed for both in the catalogues of the main suppliers). V8 pads are slightly larger than the MGB pads and fitting them to the MGB (they do fit the caliper) gives a slight improvement in braking.

Hi Gordon
I agree with Peter and Paul that your servo problem is Air related. It is important that the hydraulic slave cylinder outlet port inclined upwards between 25° and 45° from the horizontal plane. Just checked the angle on my 74 b with factory fitted servo and it looks like the angle is about 25degrees. Hope this help sort the problem.
Best Regards
Mike Barclay

Sorry my earlier post wasn't any help as my BGT has an integral servo but I do know that the angle referred to is crucial to successful bleeding.Have you tried pressure or vacuum bleeding?
. Vic Butler