Brakes wont keep pressure

[Danny Roff]

hi,
just replaced all brake cylinders including master all shoees and even though i can build pressure in the system it keeps failing....
found and fixed all leaks
bled system 4 times

after a few pumps pressure builds but then on next pump pedal hits the floor?

tried shouting and swearing and spilling brake fluid on myself....this didnt work

please help

[bmcecosse]

Not using silly silicon brake fluid by any chance ?
There must be a fault in the master cylinder - or you aren't managing to bleed all the air out of the system.

[Neil MG]

Definitely not caused by the type of brake fluid used!

It does sound like your master cylinder needs new seals (or replacing) or you do still have air in the system. Did you use an eezibleed, highly recommend if you have a spare cap to adapt. If you are doing single handed by pumping the pedal, air can get sucked back through the bleed nipple threads.

BMC trains his cars to bleed themselves while he drinks tea!

[bmcecosse]

The silicon fluid is renowned for being difficult to get a 'hard' pedal - although this does sound worse than that.

[Danny Roff]

my master cylinder is brand new.... i do have the old one so i will look into making my own ezbleed fitting....thanks for the advice


round 2 this evening.....will let you know how it goes

[Alec]

Hello BMCE,

"The silicon fluid is renowned for being difficult to get a 'hard' pedal"

That is only believed by people who have never used it.

Danny,

it sounds as if you till have air in teh system, did you bleed the longest line first, i.e. nearside rear, moving shorter each time and ending with the offside front?

Alec

[beero]

Have you adjusted up all the shoes?

[Danny Roff]

hi, spent another evening on it last night and found the following

1, some drums spinning too easy --- so i adjusted shoes inside using little screw through hole in drum
2 if i didnt let the pedal return fully it maintained pressure????? so using two spannes i adjusted the length of the plunger rod making it longer and giving me a pedal


admitedly the pedal is a little spongy so another blled is on its way but i have all wheels stopping


gonna run her up the yard tomorrow to see how well they stop while driving but hopefully its there

just fix the horn then MOT tuesday (fingers crossed)

thanks for your advice

btw i used DOT 4 fluid

[Kevin]

hi, spent another evening on it last night and found the following

1, some drums spinning too easy --- so i adjusted shoes inside using little screw through hole in drum
2 if i didnt let the pedal return fully it maintained pressure????? so using two spannes i adjusted the length of the plunger rod making it longer and giving me a pedal

admitedly the pedal is a little spongy so another blled is on its way but i have all wheels stopping

btw i used DOT 4 fluid

There may be a bit of a clue in what you say, the shoes may not be centralised properly, and your post suggests that you had not adjusted them in the first place.
Try spinning the wheels with a second person pumping the pedal to make sure they are centralised and then adjust them, if you find they are still not coming full on you may have to file the leading edge a fraction as they may only be biting on the leading edge, this is not unusual as most drums have a bit of wear in them.
I assume you didn't overdo the rod as you should still have a bit of free play on the brake pedal otherwise you may get some binding.

[MarkyB]

The type of fluid used is of no consequence beyond allowing some hobby horses to be ridden.

There must be some play in the pedal/ pushrod with the floor fitted too!
Hearing a noise when turning the road wheel is fine, any significant resistance, turn back a click.
It's quite hard to get the shoes in the right place without using the brakes a bit as Kevin says.
Invariably new brakes need at least one revisit after they have had a chance to bed in.

[bmcecosse]

[Sam_Finlay]

Can anyone enlighten me as to how one makes an " eezibleed "? Does it involve an elevated remote reservoir connected via an adapted master cylinder cap?

I have fitted new shoes, cylinders and pipes all round plus a new master cylinder and have spent all afternoon trying to get a firm pedal using the advice from various posts on the forum but to no avail. Have bled them twice and got as many bubbles running up into the clear plastic pipe connected to the jam jar via the nipple second time as I did first time. No sign of leaking fluid anywhere.

Feeling particularly clueless this evening.

[rayofleamington]

No sign of leaking fluid anywhere.

have a look in the m/c reservoir whilst pumping fluid through (being careful to avoid a face full of brake fluid from the little fountain you get at the start of m/c travel)

If you see an occasional bubble rise into the reservoir, then the fault is definately the m/c.


As for original poster - adjusting the m/c pushrod is only stopping the m/c from working properly. When it is its 'home' position the reservoir is connected through to the brake lines, and this is essential to allow the system to cope with temperature changes and wear travel. Basically preventing the m/c from reaching its trest position is like keeping your foot on the brakes, and this is masking the problem and not removing it. To remove the problem you need to remove the reason it needs to be pumped up. That can only be due to air, free travel at the cylinders or faulty flex hoses.

To get a very firm pedal, the shoes need to be a perfect match to the drums - you won't get this with new shoes! The best you can expect is a springy pedal until the shoes have fully bedded in. With the air removed and travel adjusted (maybe even over-adjust for the new shoes) you shouldn't be able to get the pedal to the floor.

A few years back I fitted new drums, shoes, cylinders, hoses, pipes, m/c and silicon fluid all in one go - despite all the warnings about silicon fluid (from people who have never used it) I had no problems.

[Danny Roff]

hi, had some friends helping me try to sort the brakes again today still having no luck

we had to top up th MC so much i ended up leaving the filler cap off

should i be concerned about the little eruption of brake fluid that squirts out?
does this indicate any issues or just normal function


im gonna strip the whole master cylinder out again i think, recheck seals and start again

any further advice would be great

[Alec]

Hello Danny,

if the master cylinder is new, i wouldn't strip it just yet.

Set the free play as it should be then bleed from the furthest wheel, one at a time. Before I had an easy bleed I never bothered with the jar and tube, just pump up the master and when firm open the bleed nipple, the pedal will go to the floor and must be kept there until the bleed nipple is closed again. Repeat the cycle until all the air is out then onto the next wheel and so on until the job is done. Really it is very simple as long as the pedal is not allowed to come up until the nipple is shut and the reservoir is not allowed to run too low. Shouldn't take more than about a quarter of an hour to do.

Alec

[bmcecosse]

Exactly as Alec describes - never failed me in the past when bleeding a car after a brake rebuild. Of course, routine work is done 'by gravity'.......

[Danny Roff]

well ive been doing that process for about 2 weeks, 5 times in total for atleast 2 hours each time

its not the method i have problems with its issolating the drop off in pedal pressure

thanks for your help tho

[bmcecosse]

Seal the two pipes exiting the master cylinder - bleed them out - is the pedal solid now ? Then connect the rear circuit and bleed it through to a solid pedal, then add in the front circuit..........

[Sam_Finlay]

I almost had a major falling out with mine at the weekend when I couldn't get a firm pedal but now think that I may have been opening the bleed nipples too much and was letting air back in via the threads.

They are fine now but only after getting someone to sit in the cab and pump & hold down on demand while I worked my way round from longest pipe length to the shortest and only just "cracking the bleed nipples open" rather than giving them a quarter turn. Took about 10 to 15 minutes with a load of air coming out of the nearside front this time.

Still don't know what an ezzibleed is though.

[Danny Roff]

thanks man

an eezibleed is a tube that screws onto your master cylinder attatched to a botlle of brake fluid attatched to an air valve
which you connect to a tyre.
the tyre air pressure forces the brake fluid through the system eliminating the need for the "friend" who presses the brake pedal

unfortunately they dont make a morris fitting for this system so i made my own out of an old MC cap

still no luck.....keep posted for saturdays trials[frame][/frame]