No Brakes

Ok well there is some…

I have a mk1 1.6 cab and my brakes are shocking!!
My pedal is extremly spongy! Under braking in need to pump the pedal to stop or else it slowly pushes right to the floor. If i am stationary, e.g at traffic lights by putting my foot on the brake pedal slowly but surly it pushes right to the floor. If i then take it off for a few seconds it frims up again.
I in the last few months i changed the rear shoes, and recently replaced the non-return valve from the servo to inlet manifold. A while back i bleed the system as the mot guy reconed there was air in it.
Would i be on the right lines thinking my servo has had it?..(Although taking off the vacum pipe to it, there is a release of air)
Is there a way to check the servo?
And if i change it, is there an up rated one which fit directly on???

Any help muchos appreciated!!!

Cheers guys  

There's a section in the Haynes manual on checking the servo is working corectly.  If I remember rightly you pump the brake pedal a few times with the engine stopped, then start the engine with your foot just resting on the pedal.  If the servo is working correctly you should feel the brake pedal pull itself down slightly as you start the engine.  Would check the manual for you but I'm in london and its with my Mk 1 in Bristol (which made it though MOT this week )

Cheers

Ian

Unlikely to be the servo, but if you want to test it either way, proceed as follows:

With engine off, pump the brake pedal a good few times, to exhaust any remaining vacuum in the servo.

With right foot on the brake pedal, start the car - the pedal should sink a little as the engine provides vacuum to the servo, and it assists your leg in pressing the brakes.

NB: with your other problem, the pedal will probably be sinking anyway, so this test will have to wait until you sort that out.

The sinking pedal symptoms you describe are typical of having bled the rear brakes with the rear axle hanging down (car jacked up). If the axle is hanging, the rear brake compensator, attached near the LHS of the axle beam, restricts fluid flow to the rear brakes - you think that you've bled them properly, but they're still full of air.

You need to bleed them with the restrictor open, like the axle is level. One way of doing this is to disconnect the spring/lever of the restrictor from the axle beam, but the fastenings around there are usually stiff/rusty/siezed, so I just lower the car (without its rear wheels) onto large blocks of wood, placed under the bottom of the rear shock-absorbers. This levels the axle while providing easy access to the rear bleed nipples. Bleed the brakes as normal (start with the wheel furtherst from the master cylinder, and finish with the wheel closest to it), and then replace the wheels, and it should be ok. If the pedal is still songy, and you have no fluid leaks, then you may have a knackered master cylinder, but this is fairly rare.

Did all the mk1 have rear brake compensators, cos i had the rear axle hanging off the other day when i cleaned out my petrol tank and im pretty sure there wasn't one there! I know my mk2 had one! Some other guy suggested a knackered master cylinder!

ricrhind said

Did all the mk1 have rear brake compensators, cos i had the rear axle hanging off the other day when i cleaned out my petrol tank and im pretty sure there wasn't one there! I know my mk2 had one! Some other guy suggested a knackered master cylinder!

AFAIK, all cars with the big-block engine have one (1.5, 1.6, 1.8 ), but what year is your cabby - perhaps other cabby owners can confirm…

If you don't have one, or re-bleeding doesn't help, the it might well be the master cylinder    , but it's worth checking the compensator angle first, as it's a lot cheaper.

I had this trouble on my very first Mk1 about 8 years ago. Turned out that the rubber seals on the piston in the master cylinder were shot. replacing them all worked a treat.

Mike,

thanks all for your help
Ill check for the compensater, then have a look at me MC.
Cheers guys