Brakes

[barrysib]

Hi recently got an mgb..the brakes are treadful i renewed the front brakes but they keep collapsing. So next step is the brake servo. Im just double checking if the servo is piped up correctly. Thanks

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[Ian F]

I think that looks OK, but there are a few questions:

#what do you mean by "collapsing"?
# what did you renew so far?
# that master cylinder looks ancient and may need replacing
#the airline to the servo also looks very iffy, and has perhaps been disturbed recently?

I would probably start with that master cylinder unless you have refreshed it already

Ian F

[barrysib]

I've renewed the brake servo disc's pads and calipers. Front brake lines and flexi pipes and vacuum pipe. I've bled all 4 corners. The brake pedal is nice and firm but after a few minutes it goes to the floor.

[Ian F]

Thanks for the reply. You have replaced that servo since you took the photos I guess?

Does the pedal firm up again if you pump it several times? This might suggest air in the system. Do you get more bubbles of air if you bleed the brakes again?

Are you confident that all the joins in the brake lines are sound and not allowing air into the system.

If the master cylinder is allowing the pedal to go down to the floor it can only be two things assuming no leakages:

# the seals are allowing fluid past and therefore producing no pressure
# there is air in the system which is compressible.

I would definitely replace the master cylinder, I do think the most likely issue is the seals in the master cylinder, assuming the master cylinder reservoir is remaining full and not allowing air to be drawn into the hydraulics.

Ian F

[Jim Gibson]

Well, some of that piping ( and other things ) looks rather messy, but ...

I'm not familiar with the layouts on the various 1800 versions, and a quick search isn't finding much.

Can you post any further picture(s) of the piping layout ?
Ideally to join up the two you have so we can see what connects to what/where.
Particularly between the master cylinder and the servo.

Jim

[Not_Anumber]

Its likely to be a shagged master cylinder or there is an almighty amount of air trapped in the system which has repelled all attempts to purge. My money would be on the former.

I spent ages repeatedly bleeding my brakes a few years ago and each time it reverted to the same result you have described with the pedal going to the floor and only recovering some compsure after several more pushes. This cannot be used on the road.

Once i bit the bullet and bought a new MC it took only minuites to bleed the system and it's been fine ever since. Come back to let us know how you get on