Series 3 Adjusting brakes

The master cylinder in normal use only travels a short distance when you bleed the system the master cylinder travels further and the seals can then sometimes fail depending on the condition of the previously un used part of the cylinder.

The vehicle has done less than 2000 miles since the master cylinder was replaced, so I would hope it wasn't worn out.

I am now wondering if the fluid level in the reservoir got too low when I was bleeding the brakes. This could have caused some air to be drawn in from the top. If that has happened, I assume it means pumping all of the fluid through yet again to get it out?

I recently had a TRW clutch master fail in 1,500 miles so I wouldn't discount it completely.

Lack of use is the worst thing for hydraulic seals.

Letting the level drop and pull air in or undoing the bleed nipple too far so it lets air suck in along the thread can lead to perpetual bleeding and drive you mad.

Am I right to assume that changing the master cylinder means bleeding all four wheel cylinders yet again?

Yes, unfortunately!

If you fill master cylinder with pipe union loose to brakes get fluid to that point then bleed nearest slave that should be sufficient as long as there is definetely no air in the rest of system.

Unfortunately I still haven't managed to get any further with this as I haven't had time to go over and work on it.

I did read in the repair manual that pressing the pedal with all three flexible hoses clamped off will help you determine if the master cylinder has failed. With all hoses clamped off, the pedal will apparently still feel spongy if the master cylinder has failed.

Does clamping the flexi hoses on the wheels other than you are trying to bleed aid with bleeding?

All of the flexi hoses were fitted new in 2015, so I would hope they are too new to damage by clamping.

With all flexi clamped the pedal should be solid , undoing them one at a time and pressing pedal should show which wheel has the air in

Will clamping off the hoses on the other wheels while bleeding help with the bleeding process?

That way all of the pressure from the master cylinder will be going to one wheel. I would hope that would be more efficient at pushing the air out.

Never found any need to clamp off hose's for bleeding Only use it for stopping fluid escape when working on a brake unit. Proper brake hose clamp will not damage the flexi.
Have you tried gravity bleeding?

Back off the adjusters to close the cylinders up, just open the bleed nipple enough to get air out but not some much air can get back in along the threads, get a good seal on the bleed tube and keep the end submerged and if you can keep the level of the fluid in the bleed jar above the nipple so it can't syphon as this can pull air in between the threads or the tube and the nipple, and its a simple job........and don't, really don't balance the jar on the leaf spring then knock the whole lot over yourself while you are wedged underneath (yes I did and it spoiled my day)

Thanks for the replies. I did try gravity bleeding but couldn't get anything to come through.

I have another master cylinder to fit, when I get round to it, which may be this weekend.

It's now about six weeks since I last looked at it.

I finally got round to installing a new master cylinder any trying again over the weekend.

The pedal now feels a lot better, but it needs to be driven on the road to properly test it. Unfortunately the MOT ran out a while back. I don't want to book in for an MOT only to find that there is still air in the system.

Jam the brake pedal down and leave overnight...helped with my 101 got a whosh of air from fronts when I bled them...

Shippers said:

Jam the brake pedal down and leave overnight...helped with my 101 got a whosh of air from fronts when I bled them...

Click to expand...

I never believed that this would work, but it solved a Fiat clutch problem for me.

I booked an MOT today as it seems that all of the air is out of the system.

The vehicle stops easily when the pedal is pressed. However it pulls to one side slightly. As far as I can tell, the snail cams need adjusting as there is no sign of any fluid leaks. Unfortunately there was no way to know that without driving it. I ended up having to phone the test centre and tell them to cancel the test as I wouldn't make it.

I now have the situation where I need to drive it to adjust the imbalance out of the brakes. However I need an MOT to drive it on the road, which it will not pass without adjusted brakes.

I did adjust the brakes as described in the manual by locking up the drums and backing off two clicks. I know that it can be difficult to tell the true state of adjustment until the vehicle is actually driven.

I reckon you've still got some air in there.

Get yourself one of these and another litre of fluid. Your friendly local Halfords should have one....

http://www.gunson.co.uk/product/G4062

I've just used one for the first time on my SIII, and it just couldn't be easier. The instructions that come with it are pretty good, but tightening the 'new' cap on the master needs to be a little more than normal, and the cap on the reservoir bottle also very tight. The tyre valve connector isn't the best I've used, but it will seal with a bit of fiddling. Do do the bit where you test it with no liquid in the bottle to check for leaks. Ask everyone in the street to be quiet while you listen.

If you can lift all four wheels off the ground it'll make life a lot better. Now start with the back left wheel, back off the adjuster completely and then bleed it until you've no doubt. Then same again for back right, front left and front right. Mine was a complete new system, and it's so easy that I went round again. Now stamp on the pedal lots of times, or nick Rob's idea above with a mallet to get the shoes centred. Finally, adjust them back up to tight and two clicks off if that's what it takes for a free spin. If one wheel needs more than that then you really ought to whip the drum off and check why.

They pull until they are bedded in, then they still pull but less. They always pull after they have been standing, especially if its raining. The drums are clean metal and corrode very quickly if not used and it takes the first couple of stops to clear it. You need to do a series of very hard stops, abolutely stamp on the brakes each time, don't start gentle as this just heats the shoes but doesn't wear them in. Do it on the way to the MOT, you can always cancell if its not improveing. Take the spanners for adjusting the brakes, you can nip them up a notch before you get to the MOT.