Bleeding brakes - what am I doing wrong?

[gatsby989]

Greetings all,

I'm trying to bleed the brakes after replacing both rear cylinders. I've read and searched several threads and google. But I must be screwing something up somewhere, because I cannot get a good solid brake pedal. I can pump it up and get pressure, but there is way too much travel, and after a few minutes I'll have to pump it again to get pressure. The brake pedal was nice and solid before, so I'm doubting it's anything to do with the master cylinder.

I've tried bleeding them with shoes adjusted up as tight as I can, and also with shoes adjusted up tight, then backed off until drum no longer binds. No difference either way. Handbrake is off.

Here's my procedure. I've done this both with just a piece of flexible fuel line and a clear tube with a one-way valve. Neither works, so it must be something wrong with my technique.

1. Put tube on bleed nipple. Put other end submerged in glass jar of fluid.
2. Open nipple about 1/4 - 1/2 turn.
3. Push brake pedal down normal to quick speed.
4. Slowly let pedal back up.
5. Repeat Steps 3 and 4 five or six times.
6. Close nipple.
7. Remove tube and put it on the next one.
8. Open master cylinder filler plug. Fill up to neck. Close master cylinder.
9. Repeat process for the next wheel.

I'm going from rear passenger side to rear driver's side, to passenger front, then driver's front. I've done it numerous times now, and I've got nice clean fluid, but can't get a good pedal. What am I missing? What am I doing wrong?

[charlie_morris_minor]

Greetings all,

1. Put tube on bleed nipple. Put other end submerged in glass jar of fluid.
2. Open nipple about 1/4 - 1/2 turn.
3. Push brake pedal down normal to quick speed.
4. Slowly let pedal back up.
5. Repeat Steps 3 and 4 five or six times.
6. Close nipple.
7. Remove tube and put it on the next one.
8. Open master cylinder filler plug. Fill up to neck. Close master cylinder.
9. Repeat process for the next wheel.

the order is incorrect..

1. Put tube on bleed nipple. Put other end submerged in glass jar of fluid.
2. Push brake pedal down normal to quick speed.
3. Open nipple about 1/4 - 1/2 turn.
4. let bubbles + fluid out
5. Close nipple.
6. let pedal back up.
7. top up the master cylinder as you go
8. Repeat Steps 2 and 7 until you have no bubbles coming out.
9. Remove tube and put it on the next one.

Repeat process for the next wheel.

i know other people have other ways of doing it so this will be last post on this subject..
if you have any questions please pm me, i am not interested in getting into another discussion on this with certain people

[bmcecosse]

Hahaha..(@ charlie..) Your own method should work well enough -I can't see anything wrong with it. But if you have a 'helper' then yes the 'charlie' method is fine too.
on the handbrake - it's not just a matter of it being 'off' - it's better if you slacken off the cables, then adjust up the shoes in the hub, then nip up the cables again to put the lever where you want it . And yes - leave it off when doing the bleeding. You don't have a servo - do you??

[charlie_morris_minor]

OK i have bitten..

the reason why i do not believe that the first method works is

1. Put tube on bleed nipple. Put other end submerged in glass jar of fluid.
2. Open nipple about 1/4 - 1/2 turn.
3. Push brake pedal down normal to quick speed.
this pushes the fluid and air out.. which is what you want
4. Slowly let pedal back up.
this will suck the fluid and air you have just pushed out back in to your system

by pressuring the system, prior to releasing the nipple, it ensure that speed of fluid is great enough to take any and all air bubbles with it. by closing the nipple before releasing the pedal it ensure that the fluid and air bubbles can not be drawn back into the system

[bmcecosse]

It's the normal way of doing things - the 'suck back' should be bubble free, since they will rise to the surface away from the submerged tube end, but of course there is that risk. Not much option if you don't have a 'helper' to hand.
Of course - gravity can do the job for you..........

[Alex'n'Ane]

You can buy "one man bleed kits" which basically have a little valve at the end of the tube, to stop any suck back, imo a good investment for a few quid.

[mike.perry]

If you are not experienced at bleeding brakes then get a pedal pusher, it is the most reliable method.
If you still feel that there is air in the system after chasing round three times then leave it overnight to settle down and chances are the pedal will be firm. It worked for me on both cars.
What ever happened to automatic bleed valves? I had them on my Mini and brake bleeding was a doddle

[charlie_morris_minor]

It's the normal way of doing things - the 'suck back' should be bubble free, since they will rise to the surface away from the submerged tube end, but of course there is that risk. Not much option if you don't have a 'helper' to hand.
Of course - gravity can do the job for you..........

in my experience I have never expelled enough fluid to expel all the air out of the tube hence the bubbles are just going in and out of the nipple.

[bmcecosse]

A mug of coffee - sit back and watch the pretty bubbles.......

[beero]

Got to agree with Charlie there BMC. It was the way my old man taught me and he was a garage owner and I have never had a problem. Not saying it doesn't work for you, with all your undoubted experience.
Besides, my wife likes it when I invite her into the garage for some "up down up down up down" fun !!

[drivewasher]

The OP says he's useing a one way valve. Personally I don't like them. We use an ezibleed type air driven bleeder for 1 man bleeding.

[bmcecosse]

Nothing wrong with that method - IF you have a helper. But many don't........ In fact - my preferred method if the brakes are being 'difficult' is to pump up the pressure - then the helper quickly opens and closes the nipple - just a very short blast - and then the pedal is lifted again. Repeat as necessary. Never fails.
And yes - one way valve is well worth having too.

[Neil MG]

Possibly you are not doing anything wrong. It sounds like it may well be the master cylinder seal. If you can get a good pedal by pumping up and down a few times then just keep the pressure on with your foot. If the pedal starts to move then you know it's time for a new master cylinder. Of course if the bore is still good you can just change the seals.

[gatsby989]

Thank you all for the responses. I gave Charlie's method a try, as far as I was able by myself. I pumped up the pedal, then wedged it down with a piece of wood, and then opened the bleed nipple for just a couple seconds, then closed it. Repeat a few times before topping up the MC and going to the next wheel. At first I seemed to be making some progress, but after going around a couple times, the pedal is still not as solid as it should be.

With all the bleeders done up, if I pump it up, and keep pressure on the pedal, it remains firm. But if I let the pedal off for a few minutes, then the next time I press it, it goes almost to the floor before there is any real resistance.

I will try to get someone to help me and give it one more go. Arrg, this is really frustrating.

[mike.perry]

For the cup of tea method of bleeding the brakes the bleed nipple needs to be below the height of the master cylinder so that once it has been pumped it then gravity feeds. You therefore have to lower the supporting trolley jack as far as possible

[charlie_morris_minor]

The OP says he's useing a one way valve. Personally I don't like them. We use an ezibleed type air driven bleeder for 1 man bleeding.

the problem with the currently available ezibleed system is the kit will not fit the moggy master cylinder.

and as Neil Mg has said if you have good brake pressure after pumping, which then goes it does suggest a master cylinder problem

[chickenjohn]

OK i have bitten..

the reason why i do not believe that the first method works is

1. Put tube on bleed nipple. Put other end submerged in glass jar of fluid.
2. Open nipple about 1/4 - 1/2 turn.
3. Push brake pedal down normal to quick speed.
this pushes the fluid and air out.. which is what you want
4. Slowly let pedal back up.
this will suck the fluid and air you have just pushed out back in to your system

by pressuring the system, prior to releasing the nipple, it ensure that speed of fluid is great enough to take any and all air bubbles with it. by closing the nipple before releasing the pedal it ensure that the fluid and air bubbles can not be drawn back into the system

I agree with Charlie. The danger of method one is that air bubbles may be sucked back into to the pipes. You only need a few bubbles to be compressible and thus give a soft pedal.

Even better is the pressurised method using an "Easy Bleeder" air pressure bleeder system and a modified master cylinder cap.

[kennatt]

are you 100% certain that you are adjusting the brakes properly,badly adjusted brakes will give you the exact symptoms you are describing,air in the system usually feels like a soft pedal at all times.

[Neil MG]

If the car has been standing for a while and there were no brakes before then it definitely sounds like master cylinder. One other possibility is a brake hose swelling up like a small balloon. That's easy to see. Pump the pedal up, wedge it down like you did when bleeding and have a look at the hoses.

[drivewasher]

My feelings on useing a one way valve as he is, is that air can be drawn in on the oedal upstroke between the bleed nipple and the threads/tapered seat