Long Brake Pedal

[Badshotbob]

Hello All, recently my Moggy started to pull gradually more and more to one side. Investigation showed that one front cylinder on one side was seized, and one was leaking slightly on the other side. So, replaced all four front cylinders and replaced the shoes and drums at the same time.

Prior to changing the cylinders the pedal was firm and braking was predictable and pretty efficient, albeit one sided.

After changing the cylinders and shoes I bled the system. But the pedal is now very long and a tad spongy and braking is very poor.

I'm assuming I haven't bled the system properly.

I started at the furthest corner, pumped the pedal until there were no air bubbles visible, closed up the nipple and moved on to the next furthest.

My method has always been to move to the next corner as soon as I stopped seeing air bubbles. But maybe that's a bit premature?

Should I pump the pedal until I notice a change in the feel of the pedal? Or stop as soon as I don't see air? In other words, could you do 1 pump, see air, another pump, no air, another 2 pumps, air again, then another pump no air? In which case, how do you know when to stop? Pedal feel? 10 pumps?

Pretty basic stuff I know, but just stopping as soon as I stopped seeing air bubbles has always worked for me in the past - but it feels like maybe I've just been lucky previously?

[Andmurph]

I had a similar issue the first time I replaced all the wheel cylinders on the pickup. It turned out to be air trapped in the rear cylinders. I pre filled the rear cylinders carefully before fitting them to the car and then bled the system again. It did the job!

[svenedin]

I don't claim to be an expert in brake bleeding but I have actually just done it last week and got a good result without unexpected trouble (rare on a Minor).

I am sure you have read the very extensive discussions that have been had on brake bleeding in this forum over many years........


What were you using for bleeding? The most basic way of a tube on the bleed nipple with the end submerged in brake fluid in a jam jar or something more sophisticated?

Did you have an assistant?

You can bleed the brakes easily without an assistant using one of these: https://www.halfords.com/tools/hand-too ... 21141.html

Are you sure that there are no leaks after you changed the cylinders?

The biggest annoyance with bleeding the brakes on a Minor is the small capacity of the master cylinder and its inconvenient location. You must make sure that the level does not drop below half full or more air can be drawn in. I worked out that it needed topping up after roughly 6 to 8 foot to the floor of the brake pedal.

I just attached the Vizibleed and then had an assistant push the brake pedal to the floor as I opened the bleed nipple. The assistant holds the pedal to the floor until you have done the bleed nipple up and then lets the pedal back up. Then you repeat until you can see no air in the clear plastic tube. Then you move to the next wheel remembering that you need to keep checking and topping up the master cylinder. You can of course use the Vizibleed single handed and as it has a non-return valve you don't really need to do the "down, hold down, up" instructions if you have an assistant but I preferred to do it that way and actually watch for bubbles in the plastic tube.

Stephen

[oliver90owner]

A long brake pedal is different to a spongy one. A long pedal, but solid, is generally a matter of brake shoe adjustment. Spongy is usually entrained air. Do you have both? Bleeding is most effectively carried out with the shoes tight to the drums.

[Badshotbob]

Thanks for the replies. The method I used was the 'old fashioned' tube into a jar of fluid while someone else presses the pedal and watches the fluid level in the M/C, while I open and close the nipple and watch for air in the tube.

There were no visible air bubbles after just two presses - but I have a feeling that maybe there is more air in the system that needs more than a few presses to show itself?

Also, regarding shoe adjustment, I'm not sure if I'm getting expected behaviour. When I adjust the cams so the shoes are tight to the drum - first observation is it takes a lot of notches on the cam - which for new shoes I wouldn't have expected - doesn't leave much adjustment left to compensate for wear. The other oddity (or maybe it's correct), is, when adjusted tight to the drum, if I pump the pedal, then the drums (front) run free again. I can turn them another notch, they go tight again, pump the pedal, drums spin freely again. I would not have expected that either - unless there was air knocking about still, which after a few pumps was allowing the cylinders to retract a little?

I've bled brakes countless times on other classics, but from what I read on here it seems it's a bit of a black art with Moggys?

[svenedin]

It's true that some Minors can be difficult to bleed for reasons that aren't obvious. The trouble is that you only tend to find posts on forums from people having trouble and you don't hear from people where it all went fine. I suspect most Minors actually bleed pretty easily. Mine does.

Is your brake system completely standard? Drums all round, no servo?

I cannot really explain the odd behaviour when adjusting the snail cams. Of course the shoes may be new but if the drums are worn they will need quite a few clicks. It is also possible that at some point the adjusters from the rear have been mixed up with the front (this only applies to 8" front and 7" rears). The rear adjusters are too small. It is normal for the shoes to require centralising and this only happens once the brake system is bled and operating properly. Once the shoes centralise by applying the pedal hard they may need another click because when they weren't centralised they were locking the drum just at one point.

Sometimes the bleeding problems are caused by master cylinder problems and no end of going round in circles will work until the MC is overhauled or replaced.

Stephen

[myoldjalopy]

" Sometimes the bleeding problems are caused by master cylinder problems and no end of going round in circles will work until the MC is overhauled or replaced."
Yes, that is true. A few years ago, I replaced all wheel cylinders because they seized up after having to drive through a ford and immediately parking up for several days in a row. Basically, they started going rusty But I could not get a firm pedal. I tried on my own with a suction kit more than once, then the ordinary way with a pal. No good. I asked a classic car garage to look at it and they bled it but still no firm pedal. They advised it was the MC at fault and - all was good after that replacement! Why it failed I don't know, except I noticed topping up the old MC while bleeding caused cloudy muck to well up inside it and maybe some of that compromised the rubber seals. So a reminder to change the brake fluid before it gets too dirty, I guess

[Bill_qaz]

Try getting assistant to pump and hold hard pedal, then open a bleeder . When pedal on floor lock bleeder. This gives a stronger push of fluid to bring out trapped air.
2nd option is buy or borrow a vacuum bleeder which pulls fluid to each bleed point.
3rd option is to reverse bleed use a new unused pump oil can, filled with fluid, attach with bleed pipe to bleeder and pump fluid up to master cylinder, with cap removed and pedal released.
You will need to wrap paper towel around mastercylinder as it will over flow.
Is mastercylinder clearance set correctly so you are using full stroke?

[stuffedpike20]

It's true that some Minors can be difficult to bleed for reasons that aren't obvious. The trouble is that you only tend to find posts on forums from people having trouble and you don't hear from people where it all went fine. I suspect most Minors actually bleed pretty easily. Mine does.

Is your brake system completely standard? Drums all round, no servo?

I cannot really explain the odd behaviour when adjusting the snail cams. Of course the shoes may be new but if the drums are worn they will need quite a few clicks. It is also possible that at some point the adjusters from the rear have been mixed up with the front (this only applies to 8" front and 7" rears). The rear adjusters are too small. It is normal for the shoes to require centralising and this only happens once the brake system is bled and operating properly. Once the shoes centralise by applying the pedal hard they may need another click because when they weren't centralised they were locking the drum just at one point.

Sometimes the bleeding problems are caused by master cylinder problems and no end of going round in circles will work until the MC is overhauled or replaced.

Stephen

I fitted new drums, shoes and lockheed cylinders and the correct front snail cams and the adjusters clicked round to maximum with no more adjustment possible.
I think it is the thickness of the shoe linings. I remember in the past having to hammer the drums on after fitting new shoes with the adjusters on minimum, and having to file the edges of the linings too.
I think Mintex shoes were the last ones to have the thicker linings; but I don't think they are available any more.

[Bill_qaz]

" Sometimes the bleeding problems are caused by master cylinder problems and no end of going round in circles will work until the MC is overhauled or replaced."
Yes, that is true. A few years ago, I replaced all wheel cylinders because they seized up after having to drive through a ford and immediately parking up for several days in a row. Basically, they started going rusty But I could not get a firm pedal. I tried on my own with a suction kit more than once, then the ordinary way with a pal. No good. I asked a classic car garage to look at it and they bled it but still no firm pedal. They advised it was the MC at fault and - all was good after that replacement! Why it failed I don't know, except I noticed topping up the old MC while bleeding caused cloudy muck to well up inside it and maybe some of that compromised the rubber seals. So a reminder to change the brake fluid before it gets too dirty, I guess

Its caused by mastercylinder stroking to a part of the bore it doesn't normally travel to, when brakes are bled the travel is the full stroke, so seals can be damaged by bore corrosion.