Soft Breaks with Servo

[SimonBanks]

I have a 1964 MM traveller with a break servo fitted. I have overhauled the breaks replacing the parts where necessary. I have also bled the breaks several times. The problem I have is that when you first try the brakes after the car has been standing the pedal goes down to the floor but any subsequent use they are fine. Anybody got an idea of what is going on and how I might cure it. It is the only thing holding me up putting the car in for an MOT

[SimonBanks]

Sorry Brake not Break

[ASL642]

Sounds like you've got air in the brakes. You need to bleed them.

[Trickydicky]

Are you getting fresh clean fluid through when you bleed the brakes? if not it does appear there is air still in the lines. Continue bleeding untill you get fresh fluid at each cylinder.

Richard

[robedney]

A couple of things I vaguely remember: Is the servo mounted correctly? There may be something about mounting to avoid an air lock, or something on the servo itself you need to bleed separately. Secondly -- has it ever worked correctly? There's something about removing the "top hat" in the master cylinder when a servo is fitted. Others will know more about this, and you might try searching the forum.

[bmcecosse]

NO - leave the top hat in place.... Are you sure all the brakes are adjusted right up? Just sounds like poor adjustment to me. Remember to slacken the handbrake cables before doing the rear brakes - then tighten the cables up to put the lever where you like it.
And actually -the original spelling of the thing that stops the vehicle was BREAK - so it's not so wrong!

[brucek]

Don't do what I did many years ago - and when I was a mere novice! Fitting my shiny new disc brakes and servo I managed to get the calipers on the wrong sides - i.e bleed screw was at the bottom not the top. Couldn't work out for hours why I wasn't getting a pedal! Staring at it, after three hours of frustration, .with a cup of tea in hand, all suddenly became very clear. Well, you gotta learn somewhere!!

[welshrat]

As usual watching this thread as I have had a simular problem for the last 12 months. My minor had been sitting around for several years and I needed to replace the rear cylinders for MOT, prior to replacement I had really good brakes, I now have scary first stop, OK thereafter but not what they were before changes. Hand brake is also not what it was. There are several things I need to check out when the weather is a little better, first is check if air is trapped in the cylinders as had not considered where bleed nipples are located (read this on another thread), also aware that there is a possiblility of servo failing and fluid leaking internally.

[kennatt]

brake pedal to the floor on first application is the classic sign of poor adjustment,everybody goes down the air in the system route,air in the system gives a soft springy pedal,if the pedal is firm after the first push as bmc says adjust the brakes.air can be compressed hence springy pedal, fluid can't hence once the first push has got the shoes out to the drums then you get a hard pedal

[IslipMinor]

You could try to adjust the brakes up 'tight', that way there can be no movement and then bleed the brakes until no air appears. Start with the LH rear, then RH rear, then LH front and finally RH front. Do you have a bleed nipple on the servo? If so this one is last. Then re-adjust the brakes afterwards.

The top hat valve, or more formally the 'residual pressure valve' is defintiely required for drum brakes, with or without a servo, and defintiely not required when front discs are fitted, again with or without a servo.

How are you bleeding the brakes? The most reliable way is with 2 people, and is to open the bleed nipple, slowly press the brake pedal down then tighten the bleed nipple before letting the pedal return. Repeating until clear of air. Unless of course you are using any of the pressurised systems, when it is normally a matter of going round the bleed nipples in the right order a couple of times, making sure there is always fluid in the master cylinder.

[Alex'n'Ane]

Try bleeding the servo with someone putting some pressure on the brake pedal.

[SimonBanks]

Thanks All
Have bled the brakes again
Also re adjusted rear brakes.
I appear to have lost the soft pedal but now the rear brakes stick on after running only a short distance (rear axle on stands) but release shortly after stopping. grrrrr

[Alex'n'Ane]

Try bleeding the top servo outlet again, I had a similar issue.

[bmcecosse]

Get rid of the silly servo..........