50 replies to this topic

[garysmoc]

Sorry unsure what the yolk is. I didn't do this bit of the job but mini specialist said with roll pin and Clevis pin fitted, the pedal was fine.

The fluid comes through to rears until bullhead valve restricts it, which seems to be about 6 inches along clear tube on bleed nipple. When you press the pedal, it really stiffens up until you stop and then it goes slack again. I think the bulkhead valve is doing what it's meant to here. This seems to be only time pedal give any resistance. The brakes are worse in reverse than forwards so sure the bulkhead valve is plumbed correctly.

The gunsons eezibleed manual mentions 3 cars only in it instructions and say for the mini, you must fill the cylinder with fluid before fitting. This didn't happen and it went on dry. I am suspicious there is an air pocket in the Pistons in the master cylinder which moves a bit during use and then finds its way back to the top again.

I think I may remove master cylinder and fill with fluid and then refit and try bleeding again.

[Stu.]

The Easy Bleed pressure for the spare tyre should easily be adequate to push the fluid though the rear brakes.

 

You must make sure the master cylinder is full, and do not allow the level of the fluid in the Easy Bleed container to get below minimum or you'll just be dragging more air in.

 

I still think its air in the system.

[garysmoc]

The cylinder was filled to the brim and I never let the easy bleed bottle fall below half way. I agree is probably is trapped air. I have a volunteer to help to tomorrow who has had the same problem on a similar mini recently and cured it.

[garysmoc]

After rebleeding all brakes using easy bleed and also pressing pedal no air came out, although small black floaters seem to be coming out of one rear wheel cylinder.

I have had a breakthrough, the pedal if fully released and the pressed goes straight to the floor. If you pump it a couple of times it comes back to half way and holds the pressure. If you slowly release pedal there is a click and if you let pedal go above this and then depress it goes to floor again. I managed to drive it using left foot braking and not letting pedal rise above click and brakes are really sharp. Release pedal and repress and hits floor.

The replacement master cylinder is different to original and looking at a exploded diagram the Clevis pin is longer on the old obsolete type that the new one. I think the pedal is coming back too far and allowing a gap to,form in cylinder, which once pumped closes.

All the part suppliers state this cylinder is the correct replacement for the type which had the nut on top, but given the pedal travel seems to be related to this, I am not sure.

Does anyone have any more thoughts on this?

[Ivor Badger]

sounds like it needs new rubbers in the master cylinder

[garysmoc]

The previous master cylinder, which had been replaced by former owner had exactly the same fault. This was the same type as I have used this time.

[garysmoc]

Since my last post I have made a temporary fitting to extend piston where it fits to pedal. This was not successful as the angles became wrong to work brakes properly. Quite by accident I left a bolt in the cavity where the brake pedal comes back down and the brake pedal did not return to usual height. The brakes then worked fully with no air or sponginess. I have cut a piece of wood and placed in cavity and test driven car and the brakes are really sharp, with no pulling, sponginess, fade or issues. However with amount of travel to make them work is just a couple of centimetres and the pedal is being held 1/2 way down.

My conclusion is the issue is definitely a problem that when the pedal returns to normal height, the question is why and how to overcome it. To save reading the whole thread, every element of this split front rear non servo drum brake system has been replaced, except the lines and flexible hoses.

[Dr s]

To get a good pedal I always bleed with an eezibleed then using a bit of wood against the cross member and pedal wedge the pedal down over night. I don't know why it works but it seems to.. I assume it lets any bubbles left percolate back up and out of the master

[Ethel]

The pedal just pushes against the piston, it isn't physically joined. Jacking it up to see if all brakes, front & rear, may tell you something. It does sound like it may be Master cylinder.

[carbon]

Another suggestion as a bit of a long shot, the adjustment of the front brake shoes is pretty critical on the twin leading shoe brakes as they are large diameter cylinders and can take up a lot of fluid if they are slack.

 

Take front drums off, check the eccentrics are correctly positioned on the shoes, and make note of which direction it needs to be turned to take up slack. Put drums back on, then adjust both shoes on both sides to the point where the adjuster can't move any further (ie solid), then check if this has made anyu difference to the pedal travel.

 

You may have have done this already...

[garysmoc]

Thanks for all suggestions. I have tried two brand new genuine ap master cylinders and also adjusting brakes to maximum and that all four wheels are locked and still pedal hits floor on first press and then subsequent ones are half way. The pedal stays solid at half way but if you ever fully release, the next press hits floor. All brakes have also had hoses clamped off one by one and this makes no difference. There is no fluid loss anywhere. The master cylinder, front rear bias valve and all cylinders have been bled three times using easy bleed with 20 psi, so confident no air.

One suggestion by email is that the new front back plates may have been supplied without small coil springs, so will check this.

[sledgehammer]

now running out of ideas - I would blank the master cyl off , bleed it , then check pedal 

 

if good - problem is some where else

 

can you take a pic of the master cyl & pipes around it ?

 

another idea is to bleed individual unions (have a rag to stop fluid getting on paint work) , may get more air out that way

 

stick with it - it's something simple , just we haven't thought of it

Edited by sledgehammer, 12 July 2015 - 10:35 AM.

[Dr s]

You are adjusting both front adjusters? There is a top and a bottom one from memory?

If you are happy it's bleeding properly then I'd be swapping out the hoses, it can't be much else?

[garysmoc]

I'll try and take a pic when I next work on car at weekend. Pipes are correctly plumbed for later cylinder. I have tried bleeding unions with a rag, but no air was present.

Both front adjusters have been adjusted, but there may be some work to do here, so will remove drums. Check all springs are present and then see what happens.

With a block in the rear circuit and individually clamping of each of the front flexi hoses, it makes no difference to pedal travel

[garysmoc]

I have left a block of wood under the brake pedal to stop it returning to full height for a week. I have also taken drums off and checked all springs are in place and shoes are seated correctly. I have readjusted each of the adjusters and now I have half a pedal again. I forgot to remove block of wood before adjusting, so can't tell which action caused this improvement

Separately I think I have over adjusted the adjusters, one on each side as the now seem quite loose. Is this possible and how do I rectify. They seem to adjust up, but then you can add several more quarter turns, which I am sure is not correct. They are brand new backplate set ups.

I am still not happy with half a pedal and not sure it will keep it, As achieved this twice before and then it faded upon driving.

Any more comments would be appreciated.