letting gravity bleed the brakes

[bmcecosse]

The master cylinder retains a residual pressure designed to keep the shoes close to the drums. If standing for a few days the pressure can drop away - and so yes that first pump will often be quite long - but should then stay firm for the rest of the day.

[lesrollins]

All wheel cylinders, master cylinder, brake lines,bleed nipples,brake shoes, springs,copper washers are new. And I have replaced all three hoses with the stainless steel braided goodridge ones as I think they don,t flex under pressure like the normal rubber ones So I don,t think any of the seals should be letting any air past unless they are faulty from new. It is not loosing any fluid as I have checked the master cylinder and all the joints are as tight as I want to go. Tried it again this morning and the pedal still went to the floor on the first push but pressed a couple of times and the pressure is good. The car is on axle stands all the way round at the moment without any wheels on so I have good all round access to everything.

[MarkyB]

Sounds like you have all the bases covered.
You could try slackening the adjusters off then give the pedal a few short sharp jabs with your foot.
This may help centralise the shoes. If everything else is working, and the car is securely on stands you could "drive" it and use the back brakes a bit.

If no more air is coming out, then the issue is one of adjustment or bedding in of all the new bits.

[lesrollins]

Will this help to put fluid in the rear cylinders, as I seem to read, because the bleed nipple is located in such a position the fluid is difficult to get into the cylinders and I just wondered if I may still have air in the rear cylinders.

[bmcecosse]

Highly unlikely - I know others have written about this - but I've never experienced it and I've changed many a rear cylinder. I really do think this is an adjustment issue then - given that you have renewed everything! Slacken back the handbrake cables and then turn all the adjusters up so the shoes are rubbing firmly on the drums - barely able to turn them - and try that.

[kennatt]

I know that air can cause these sort of symptoms but generally the problem you describe is more like adjustment,Air in the system gives a soft feeling even after several pumps,its caused because air can be compressed but fluid can't,so if the pedal is rock hard after a few pumps then there is no air in the system as you would still feel that the pedal is soft.Pumping the pedal pushes all the shoes out to contact the drums,then next stroke its hard.As bmc says the system is designed to hold a slight residual pressure to hold the shoes near to the drums,could be that the master is faulty and not doing this,how long does it hold a good pedal for,does it just go down overnight or after a few minutes,I know what I would do,although bmc will tell you not to,I would clamp up each hose in turn to try to isolate which wheel was causing the trouble,so I would know where to concentrate my efforts,In 45 years of dealing with brakes as both qualified mechanic and then as a hobyist I have never damaged brake hoses by clamping as long as you use very gently pressure,they only take a slight nip up with a clamp to seal them enough,if the hoses were to be damaged then it was long past the time they should be changed anyway,thats what I would do ,anyway its up to you

[bmcecosse]

I think it is brand spanking 'braided' hoses...........

[xpress]

the posts made interesting reading. reading the posts made me realise something. i don't know exactly what a firm pedal feels like on these cars, i know what a firm pedal is on abs cars, or servo assisted, but new to morrises. i acutally think my pedal is firm, however, it's a bit low but this could be me not being used to these brakes, but these brakes sure stop the car and lock all the wheels. and were bled properly using the pedal down, tighten nipple, pedal up, open nipple, pedal down routine as stated previously.

one thing of note, when i adjusted at the drums, i click adjusted fully so drums couldn't move, then backed off one click.

not a seasoned morris driver, but i would say that the pedal feels quite low when i press it but has never hit the floor therefore i assume the brakes are okay and the tester may not have jammed them on hard enough for the test.

if charlie is passing by sometime, maybe he can have a feel of my brakes and give his opinion of them?

[lesrollins]

Thanks for the advice Kennatt but I don,t think i,m going to go down the route of clamping brand new braided hose. I think I will be following bmcecosse advice. But it will have to wait until Sunday this is my next my next day off and I will get the wife to assist again so I will let you know how I get on.

[MarkyB]

If the pedal has never come up very high, even when it was hard I'd take a look at how much play there is in the push rod that operates onto the master cylinder.

To actually see it you need to remove the gearbox cover but, you can get a good idea by operating the pedal by hand,
For part of the movement there will be no resistance except the return spring, then contact with the MC piston, then moving that until the fluid stops it.

There needs to be some free play but nothing like as much as for the clutch because the master cylinder is fixed unlike the bite point of the clutch which will change as it wears.

[bmcecosse]

After the first push in the morning - the pedal should have short travel and effectively be 'solid'. Pushing really hard will swell the flexi pipes slightly - yes - even the braided ones - it's just a braid over a rubber pipe! There used to be 'double green band' flexi pipes available - specified for rally use on Cooper S etc - but doubt we can get them now. I personally dislike the braided ones because you can't see the condition of the rubber pipe. And I believe their effectiveness is much over-rated anyway.

[Stig]

The braided ones I fitted when I built the Sprite are PTFE, not rubber.

[bmcecosse]

Ok - well - it's still a kind of 'rubber' to me !

[les]

Are you saying the first push in the morning should be softer than the following times Roy, or have I read your post wrong? If not I'd better let some air into my system!

[bmcecosse]

Yes - first push forces the pistons out till the shoes hit the drums. The master then retains a small pressure (~5 psi I believe) in the system - this is a kind of 'automatic adjustment' BMC cleverly built-in - to hold the shoes near to the drums so that subsequent pushes are nice short travel. Overnight (or maybe even during the day) that pressure leaks away and then the long push is required. It really is a 'hint' to you that the brakes need adjusting! It is of course the bane of those who choose to fit disc brakes to their Minors - because the retained pressure causes the pads of disc brakes to drag on the discs causing overheating and fading!!!!!!! The very thing they are trying to avoid! No such problems with the fantastic Wolseley 9" drum brakes I'm pleased to report!!

[xpress]

how do you adjust the level of the footbrake? mine seems a bit low, but short travel to put the brakes on.

[kennatt]

read markybs post above

[les]

Roy, if the shoes were already 'near' the drums or in other words adjusted correctly, I presume this first push on the brake would be the same as subsequent 'pushes' ie: hard? As I have not found this first push business apparent on my vehicle since setting things up properly, I was puzzled to observe that you accept as correct, there being a soft pedal initially.

[kennatt]

if I let mine stand for two or three days then the first push goes about half way down next is at the top and hard,its allways been like this, after three or four(forget now) rebuilds its not just the position of the brake shoes,which don't move much its the fact that the pistons draw back inside the bores of the cylinders when stood inactive,hence the residual pressure built into the system from new to hold them out.

[bmcecosse]

As I said above - the 'long push' is a hint that the brakes need adjusting. If the brakes are correctly adjusted up - there will be no 'long push' . Simples!!