5 replies to this topic

[AC&SONS]

Looking to change the brake fluid on my son's 1977 Mini 1000. It is a single-circuit braking system, and I have read elsewhere about the pressure-limiting valve at the rear; does this affect bleeding the system? Planning to buy an easy-bleed kit - any ideas how much fluid it takes to refill the system?

Any tips or hints would be appreciated.

Thanks

[SA MINI]

I can't remember how much fluid I used.
But I did have issues with the pedal turning soft .

I bought one of the easy bleed kits of eBay & that done the job perfectly.

[tiger99]

You can do this without problems with the PRV, or getting air in, or making a mess. You do need an Eezibleed and lots of fluid, a piece of clear tubing that will fit the nipples, and a container for used fluid, also some kind of syringe,

First, suck all the fluid out of the reservoir with the syringe, to avoid diluting the new fluid. Then fill it right up with fresh fluid. (You can suck it out and refill again, to make it even cleaner.)

Fill the Eezibleed, and apply to the reservoir. You will need a source of air, a tyre deflated to the correct pressure is ideal, so let some air out of the spare. (Don't forget to reingflate afterwards!). From memory it is 20 psi max for the Eezibleed. Fit the tube to a rear nipple, end in the container, and open the nipple for a while. If someone is watching the fluid level in the Eezibleed, you can keep going until fresh fluid emerges. The colour difference is quite obvious. If not, stop and check periodically, refill each time. If the reservoir becomes empty at any stage you have a far worse problem, of bleeding, not just changing fluid.

When you have fresh fluid at one rear nipple, fill up again and do the other rear, which will not take long as there is only the pipe run from the limiter to the wheel cyliner to flush.

Fill up again, and do front right, and again for front left. Job done.

Note that the Eezibleed pressure is way below the setting of the pressure limiter so it will not activate, and fluid will pass through to the rear brakes freely. Do not be tempted to press the pedal at any stage, it is not needed for a fluid change, and might activate the limiter.

The sequence of doing the nipples in a fluid change is not necessarily the same as when bleeding. The idea is just to flush out the old fluid with new in as economic a way as possible. Getting trapped air out is rather different.

[dklawson]

On the other hand, you can do this without the Eezi-Bleed.

The method used to flush brakes without an Eezi-Bleed is what I have used for years to both bleed and flush brakes. It requires..
Two people,
a catch jar,
lots of clean brake fluid,
clean,clear plastic tubing,
a wrench for the bleed nipples, and
teamwork.

Start by topping up the master cylinder reservoir with fresh fluid.
Start at the bleed nipple furthest from the master cylinder.
Fit the clear tubing to the first bleed nipple and place the other tubing end in the catch jar.
From under the car you open the bleed nipple 1/2 turn.
Once open you call to your assistant "Down".
You assistant SLOWLY presses the brake pedal down. SLOWLY.
When the pedal reaches the floor your assistant hold the pedal in place and calls "DOWN" back to you.
Once you know the pedal is down, you CLOSE the bleed nipple and call back to your helper "RELEASE".
Your assistant releases the pedal so it rises to the top.
When the pedal is fully up your assistant calls "UP" back to you so you know to re-open the bleed nipple.

Repeat the above steps about 4 or 5 times, then check the level of fluid in the reservoir.
It is VERY important not to let the reservoir fluid level drop too low. You do not want to suck air into the system as this forces you to repeat what you have already done. Make sure to keep the reservoir nearly full.

Bleed each nipple (corner of the car) this way while you watch the color of the fluid passing through the clear tubing. Once you see the dark old fluid replaced by fresh clean fluid you are done and can move on to the next wheel. Work your way from the wheel furthest to the master cylinder to the one closest to it. After you bleed the last wheel make sure you re-check and top up the level of fluid in the reservoir.

When the system is already full of brake fluid, the rear proportioning valve does not have to be a problem. Follow the steps above keeping in mind to keep the reservoir nearly full and press the brake pedal down slowly. If you take those steps you will be able to flush the system without the Eezi-Bleed.

[tiger99]

That will work perfectly well too. Only minor snag is that it needs two intelligent people. Sometimes Eezibleeds are easier to come by, in parts of the UK at least...

Key thing, as you say, is to tighten the nipple while the pedal is down. A lot of junk is sold to facilitate bleeding, such as one way valves, and, like snake oil, none of them work, because on the return stroke air is drawn in around the thread on the nipple.

A vacuum bleeder, currently fashionable, which just sucks from the nipple into a jar, might work too, however I have some doubts about them, because the wheel cylinder seals have a wedging action under pressure, but under vacuum they might let air in around the edge, unless the rubber exerts sufficient pressure by itself. OK on discs though, the square section seal is a tight fit and in any case will made a good seal on either face of its groove.

[bmcecosse]

I wouldn't worry about the syringe - just run the level down with bleeding then fill with new JUST BEFORE the fluid runs out in the reservoir... I just use gravity to do my bleeding for me .......