Brakes not working

[bmcecosse]

Yes - that' s a well known Mini 'fail ' - I used to advise on that pretty much weekly on the Miniforum!

[panky]

Failed again

[kennatt]

[quote="stag36587 No difference whether both or either side clamped - I wonder if the 3 way union is faulty![/quote]

Clamp the rear flexy see what that does.(90% of the fault you have is usually down to poor adjustment)

[les]

Time you called someone in!

[bmcecosse]

I dunno who that 'someone' would be - because it's all been tried - or at least reported as having been tried.... I've probably asked before - but when adjusting the rear brakes - were the cables slackened off, then the cylinders cranked up on the adjusters (to dragging point) and only then - the cables re adjusted ? Have ALL cylinders been renewed? If so then it really MUST be down to the mastercylinder. Jono (in another place - but surely time we forgave and forgot and invited him back here..) reports FAULTY brand new mastercylinders..... So - if you plug off both outlets - is the pedal firm then ??

[stag36587]

Pedal was lovely and firm with front blocked off. Rear brakes are fine. All brake components are brand new. All unions checked and double checked, system bled correctly several times with adjusters up tight. Checked rod into the master cylinder/pedal travel etc. Fluid pumps through the front pipes well when pedal pressed which would suggest master cylinder is ok. Still must be air getting in somewhere.

Anyway what I really need is an uninterrupted day or two when I can lock myself in the garage and go through everything yet again. Either I've missed something really obvious or there's a faulty component. I'll also try rotating the drum on the flex hose as someone has already suggested.

Just one thought - the bleed nipples on the front cylinders are a different spanner size to the rears, i.e. 10mm front (surprised it was metric) and 7/16in at rear. Is that right?

Can someone please confirm right fluid level in the master cylinder? It's up to the bottom of the filler neck at the moment,

Thanks everyone for your suggestions, much appreciated.

[bmcecosse]

Hmm - so when you push the pedal down - do any air bubbles appear in the bleed jar ?

[stag36587]

Eureka! I think. I didn't expect to have any time to work on the car today but thought I'd at least get the front up on axle stands so that when I did have some time I wouldn't have to do any prep first.

I decided to look to see what happens when pressing the brake pedal with the drums removed. I adjusted all cylinders up tight. Curiously, on the nearside both cylinders opened an equal amount but on the offside, the front cylinder opened wide but the rear hardly at all. Then I noticed a tell tale puddle on the floor - it appears that the front cylinder is leaking but only when able to move out unrestricted by the drum.

Does this help to narrow down the problem and (another) new cylinder will fix my problems once and for all?

[bmcecosse]

Indeed! The seal may be faulty and drawing in air! Are they 'genuine' cylinders (which have the bucket seal) - or repro which only have an O ring.... ?

[stag36587]

Indeed! The seal may be faulty and drawing in air! Are they 'genuine' cylinders (which have the bucket seal) - or repro which only have an O ring.... ?

I paid extra to get the genuine ones

[bmcecosse]

Quite right - the repros don't seem to last..... However - what did you actually get ?????

[DAVIDMCCULLOUGH]

If its the genuine ones you could just order a seal

http://morrisminorspares.co.uk/shop/pro ... cefaa71b60

If your in any doubt though order a full cylinder.

Hope your getting there!!

[stag36587]

They were Lockheed from ESM. I'll get a complete replacement for, hopefully, peace of mind.

[bmcecosse]

Fingers crossed for you.... And they say Triumph Stags are troublesome........you've certainly had your trials with your Minor !

[bmcecosse]

Double post for some reason...

[stag36587]

Thanks Roy, the brakes have held up the restoration for months but hopefully I can now get on with things a bit faster. The Stag has had its moments too over the years, though the brakes seemed really easy to replace.

Now, more important things: Happy Burns night. The Haggis and cranachan tasted so good today

[bmcecosse]

As a TR7 owner - I can appreciate the 'fun' you have with your Stag. Although in fairness - my TR7 has been very good to me - so far.......

[kennatt]

Eureka! I think. .

I decided to look to see what happens when pressing the brake pedal with the drums removed. I adjusted all cylinders up tight. Curiously, on the nearside both cylinders opened an equal amount but on the offside, the front cylinder opened wide but the rear hardly at all. Then I noticed a tell tale puddle on the floor - it appears that the front cylinder is leaking but only when able to move out unrestricted by the drum.

Does this help to narrow down the problem and (another) new cylinder will fix my problems once and for all?

Totally confused as to what you have done ,its impossible to adjust the cylinders up tight with the drums off.theres nothing to adjust up to I suspect all you have done is to turn the cam and its pushed the shoes out away from the cylinders,this is not adjusting if you see what I mean.
with the drums off when you press the brake, yes the cylinders will work,and if you continue to press the brake again it will throw the pistons right out of the cylinders and loose all the fluid and introduce air into the system. Its common for one piston to move and leave the other in place ,its because the system is trying to ballence the pressure across all pistons,and is looking for the brake drum to stop that one so that the other one can move.
This is how all systems work ,untill at least one piston touches a drum,front or back ,non of the others will move(They do slightly but will not be pressured up onto the drum) when all,in the case of a minor,6 pistons are in contact with the drums,then the pedal will go hard and equal braking on all drums will ballence out.Thats why all the shoes need adjusting up close to the drums to prevent a long pedal travel. In the minor there is a built in valve(in the master) to hold a slight residual pressure to hold the shoes close to the drum. This pressure drops after standing and its again common to get a long pedal stroke first thing and then for the pedal to be hard for the rest of the day.
The fluid on the floor is 100% a result of one piston being pushed too far out of the cylinder.IE the front upper that moved right out. If it was leaking before there would have been signs of fluid on the inside of the drum when you took it off. You have now I suspect let a lot of air into the front of the system and will need bleeding again. Thye way to check that pistons are free,is that you must make up a clamping system (Wire round the cylinder) to limit the free movement of the piston and stop it from being pushed out and to act as a temporay drake drum. You can not check by just removing the drums.
sorry if You are aware of this but looks like you are struggling with the basics of how the brakes work,no offence intended.

[stag36587]

No offence taken Kennatt, if me and others can learn through this thread then that's useful. I've bled quite a few brake systems over the years but never had this trouble. I was aware of danger of pushing the cylinders out too far, what surprised me in this instance is just how easily and far the one cylinder moved (on one push on the pedal only) compared to no movement on the other one. At the same time, both cylinders on the nearside had moved out slightly and evenly.

So assuming you are right I am still left with pedal travel that firms up after 2-3 strokes but goes long again after about 30 seconds.

[bmcecosse]

Can you clamp the shoes together to replicate the drums - but so you can see what's going on - and try bleeding them like that... ? Obviously don't press the pedal too hard...