bleeding brakes...pissing me off!
Turbo Mini Forums

Righty...the setup I have is a single line brake system, twin leading shoes at the front with a bias valve on the rear subby.

Parts ive replaced...all front and rear wheel cylinders, all brake lines, and ive now just resealed the master cylinder.

I took the car for a spin yesterday (on a private road ) and the first time I tried the brakes they worked fine, second time not so much, next time I had to pump them. I tried the pumping the brake method, then holding my foot on the pedal and it seemed to stay in the same place and not creep to the floor. I noticed some fluid around the clevis pin so I though I would replaced the seals.

When I took the master cylinder apart the bore looks perfect but when I tried the seal in the bore, it went in really easy (well compared to my clutch cylinder that I have resealed) so I thought I'd replace the seals.

On replaceing the seals, the new ones feel like a much tighter fit, so I figured that was the problem.

I have now bled the system, using a vaccum pump, but after the first go the pedal still went straight to the floor and I could hear squelching from the master cylinder. I tried bleeding them a few more times and the pedal felt better, but still not perfect. I then tried to bleed the brakes the oldchool way, opening and shutting the bleed nipple, whilst pressing/lifting brake pedal. No air came out of the front lines, but some came out of the back.

The pedal doesn't hit the floor anymore, but if I pump it I can feel it getting better, but if I wait a few seconds and depress it again it seems to take more travel to go solid until I pump it again.

There is no longer squelching from the master, and the pedal doesn't go anymore solid after about 3-4 pumps, but its still not right.

I am at a complete loss of what the problem could be, as it seems to be air in the system but I can't see how it can be getting in the system...has anyone got any ideas before I open my wrists up. lol

Cheers
Matt

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1/4mile in 13.2sec @ 111 terminal on 15psi

get some kind of pedal, and wedge a bit of wood between the pedal and steering wheel so its pressed down, and leave it overnight, it shouldnt work... but it sometimes does,

if you got std flexis mole grip them off one at a time and press the pedal once and hold it down , get someone to release the grips and see which one goes down the furthest

make sense ?

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crack open the pipe on the master and bleed the air out there (bit of a pain to do with multiple rags to stop paintwork geting brake fluid on it!), also if its an anftermarket nmaster make 100% sure its fully returning when the pedle is released

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Joe - will give that a try tonight.

100ev8 - that makes sense, will give that a try

Also trying to rule out everything...how can you tell the difference between a clutch master and brake master? Ive looked around and ive seen various different ways they are mounted (position of filler cap). The master im using looks externally the same as the as the one I removed, but as ive possibly ruled out everything else, could it be a clutch master instead of brake?

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1/4mile in 13.2sec @ 111 terminal on 15psi

Denis - will give that a try, ive got an old piece of brake line I can use to bleed it.

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1/4mile in 13.2sec @ 111 terminal on 15psi

From memory about the only difference in master cylinders is one has an internal return spring (brake), the other does not.

Also are you sure all the shoes are adjusted right up, if not this can lead to the needing to pump to get a pedal as you have 6 off slave cyl to pump out first.

Ive just disconnected the brake line from the master cylinder, connect a piece of brake line with a clear tube on it and pumped the brake pedal...no bubbles. I put my thumb over the end of the pipe on the up stroke to purge it through and still no bubbels.

I reconnected the brake line and pressed the pedal down a few times until it went solid and each pump I could see the fluid level go down. When I released the pedal I could then see the fluid slowly go back up..what does this mean?

Tom - I thought about that yesterday and tried adjusting the the shoes up the other day, Ive got them so they just start to rub on the front and rear, so there is no way of excess travel there from what I can tell!?

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1/4mile in 13.2sec @ 111 terminal on 15psi

You can't muddle up the metal canned type because one has the metal can offset clockwise relative to the cylinder and the other anticlockwise (to space the cans away from each other).

However, the internals are slightly different and can be muddled.

From memory it's not spring/no spring as Tom suggests but one has a valve arrangement on top of the spring and one doesn't. I think it is the brake one that has the valve and if it is missing/defective/upside down, getting them bled is very hard.

Schrödinger's cat - so which one am I ???

I would bet its all down to adjustment, Ive had drums all round on most of mu Minis and they are a pain to get right initially. On the front you have to get the same amount of adjustment on both adjusters on each side otherwise one of the cylinders will get more travel than the other causing a long pedal

I seriously doubt it!

Paul - Have you got any tips on how to adjust them up?

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1/4mile in 13.2sec @ 111 terminal on 15psi

Take the drum off and adjust both top and bottom adjusters off to the same position. Refit the drum and adjust both adjusters the same amount in small increments until you get the right feel when turning the drum. Give it a run down the road to remove any high spots from the shoes/drum and adjust them again.
Also make sure that if you have a lip on the inside of your drums that the shoes are sitting inside it rather than on it which would cause the shoe to twist and give a long pedal too

I seriously doubt it!

ok that makes sense.

How do you make sure the shoes are inside the lip?

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1/4mile in 13.2sec @ 111 terminal on 15psi

Get rid of the lip.

I seriously doubt it!

In that case I might just invest in some new drums.

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1/4mile in 13.2sec @ 111 terminal on 15psi

Do you have access to a lathe? you could skim them and make sure theyre round at the same time

I seriously doubt it!

I'm betting it adjustment too, I don't have drums all round but minisport 4 pots. I was in the same boat - they worked gone with the 2 pots good feel no issues, I swapped them bled them twice. Could I get the pedal right.... No! In the end out of desperation I thought I'd check the rear adjustment. I set them up and hey presto the pedal went hard.

Drums all round are notoriously difficult to set up. I think the Haynes has a good guide??

Paul - I do have a lathe but its too small to fit the drums on.

Ive had a bit of a result tongiht though! Ive bled all the brakes AGAIN after disconnecting the pipe from the master. I then adjusted all of the cams front and back so the brakes were jammed on and the pedal felt solid. I then backed the rears off so they are just rubbing, and the pedal still felt solid.

I then stripped the front brakes to inspect the drum/cam position, and the drums only had a tiny bit of rust/brake dust layer on the outer edge, so I sanded that off and underneath it was still smooth (no lip).

The only way I can get the drums to go on is to have the cams only just touching the shoe. Im guessing this is because the shoes and drum are pretty much new? I manged to get a tiny amount of adjustment before they starter to bind, but I adjusted them together.

I did notice that the cams on the offside have to be turned anticlockwise and I have been turning it clockwise, and it looks like the cam was pushing on the return spring.

Ive put it all back together, and the brake feels fairly solid from the first push, but it is noticably better on the second push. Im hoping this is due to a bit of air left in the system.

Overall its MUCH better than it was, it definitely feels more like a brake pedal instead of a clutch!

I'll take it for a drive along my stately home private driveway tomorrow and see how it feels. :)

Cheers for all the advice, will let you know how I get on.

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1/4mile in 13.2sec @ 111 terminal on 15psi

Well my brakes feel much more responsive now, and I managed to get them to lock up which is good.

Im hoping bleeding them one last time will help illiminate the slightly soft pedal on the first push.

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1/4mile in 13.2sec @ 111 terminal on 15psi