brake bleeding again

[JaneHibbert]

it has been done to death i can see by searching but cant find the 'whole story' of how to bleed the brake system. can somebody post me a link to a simple explanationo f how to bleed or give me a short right up? thanks

[Trickydicky]

Hi,

What work have you done on the brakes? new M/C, brake pipes or wheel cylinders?

First thing to check is that there is 3/4" free play at the top of the brake pedal.

If you have replaced the M/C then try bleeding the brakes in this order untill you get fluid flowing at each corner, front drivers side, front passenger side, rear drivers side and finally the rear passenger side. Once you get fluid flowing through following this method then bleed in the order stated in the manuals just to confirm there is no air left in the system.

If you need to or have replaced a wheel cylinder or brake pipe then simply create a air lock in the system by placing a piece of plastic over the M/C screw cap and replace the cap, then remove and replace the offending wheel cylinder or brake pipe and finish by removing the plastic and bleed in the conventional way.

Also I would not recomnened using a hose clamp on any of the flexible pipes as they end up splitting the pipes especially if they are old.

Good Luck

Richard

[bmcecosse]

I agree - NEVER clamp flexi pipes.....

[mike.perry]

If the flexible pipes, two at the front and one at the back are old, it is better to change them now rather than when they fail an MOT and you have to bleed the whole system again.

[ampwhu]

or fit a NRV each side.

[bmcecosse]

Where would one fit that?

[JaneHibbert]

two new cylinders, but the brakes are very soft. you pump them for a while and it goes hard

then... after a minute it goes to the floor again... no leaks anywhere.. you say, people, 'bleed them'.

that what I want a simple explanation of...

[lambrettalad]

do you have a servo? if so check if your losing brake fluid in to it?

[bmcecosse]

Fill the master cylinder, pump up the pressure and hold the pedal down - while your assistant opens and closes the bleed nipple on the wheel where the new cylinder(s) has/have been fitted. Only allow the pedal to come up when the nipple has been closed..... In effect the nipple is just 'snapped' open/close very briefly. A tube can be fitted and led into a jelly jar to avoid mess. The brakes should be adjusted up before starting. Are the new cylinders at front or rear?

[rcharman]

The brakes should be adjusted up before starting.

I totally agree, this has to be done first. I renewed the whole brake system on my MM and was puzzled why the brake pedal was low even after doing a small adjustment. Then I realised the manual states the brake adjusters have to be adjusted so the shoes lock the brake drum, then back off one notch. My MM brakes are perfect with no brake drag (perfect for drum type with no servo fitted).

[simmitc]

If you use a piece of hose from the bleed nipple into a glass jar with some brake fluid already in it, then (a) you will catch the ejected fluid and stop it ruining the paintwork / driveway and (b) you will see air bubbling through the fluid in the jar and know when that when it stops bubbling, then you are getting fluid only and no air. You will always get some air on the first couple of pedal strokes as it will be in the hose. Always discard the fluid in the jar afterwards, do not be tempted to re-use it.

When bleeding, ensure that the mater cylinder is topped up regularly, otherwise it is easy to empty it and get even more air into the system, having to start again from scratch.

Although it is (to me) counter-intuitive, I have read some manual that give the opposite order for bleeding - rear passenger, rear driver, front passenger, front driver. This has always worked well for me. Note that you may have to go right round the car twice to ensure that all air is removed from the system.

[Trickydicky]

Although it is (to me) counter-intuitive, I have read some manual that give the opposite order for bleeding - rear passenger, rear driver, front passenger, front driver. This has always worked well for me. Note that you may have to go right round the car twice to ensure that all air is removed from the system.

It is in the Haynes Restoration Manual, in the brake replacement section. I used the steps after replacing my M/C. I could not get any fluid to flow using the conventional method and by this time the wife was getting hacked off pressing the pedal and nothing happening.

Jane, if you are getting a stiff pedal after pressing the pedal a couple of time, then it going to the floor and you are sure you have no leaks then It is air in the system.
When you replaced the cylinders did you replace them without creating a airlock in the system? (ie, placing plastic over the screw cap of the m/c and screwing the cap back on?) or did you just replace the offending cylinders?
The only way to get rid of the air in the system is to bleed it out, it may cost you a litre of brake fluid but its the only way.

By the way, do you have a manual?
Richard

[bmcecosse]

Just because the brakes 'pump up' you can't be SURE it's air in the system. It can just be adjustment.

[JaneHibbert]

They were the back cylinders, and no I didn't put platis or anything over the master cylinder, so there is probably loads of air! ill give this a go as soon as i can and report back

[JaneHibbert]

Oh, and have just got a manual now