basic brake bleeding advice
Discussion
hi ,just need a little advice, I've been trying to bleed my brakes with no luck.
my friend is helping me by operating the pedal whilst I loosen and tighten the bleed nipple accordingly.
I've noticed that after I've cracked the nipple undone and he has pressed the pedal down , fluid is displaced into my bleed pipe as expected but then within a few seconds it all disappears back into the wheel cylinder , even with the pedal held down? this is confusing me .
the car is a classic mini with drums all round and front to rear split with a yellow tag master cylinder. everything has been replaced bar the compensator on the bulkhead .
cheers
my friend is helping me by operating the pedal whilst I loosen and tighten the bleed nipple accordingly.
I've noticed that after I've cracked the nipple undone and he has pressed the pedal down , fluid is displaced into my bleed pipe as expected but then within a few seconds it all disappears back into the wheel cylinder , even with the pedal held down? this is confusing me .
the car is a classic mini with drums all round and front to rear split with a yellow tag master cylinder. everything has been replaced bar the compensator on the bulkhead .
cheers
bruteforce1 said:
hi ,just need a little advice, I've been trying to bleed my brakes with no luck.
my friend is helping me by operating the pedal whilst I loosen and tighten the bleed nipple accordingly.
I've noticed that after I've cracked the nipple undone and he has pressed the pedal down , fluid is displaced into my bleed pipe as expected but then within a few seconds it all disappears back into the wheel cylinder , even with the pedal held down? this is confusing me .
the car is a classic mini with drums all round and front to rear split with a yellow tag master cylinder. everything has been replaced bar the compensator on the bulkhead .
cheers
So what exactly has lead up to you wanting to bleed them ?my friend is helping me by operating the pedal whilst I loosen and tighten the bleed nipple accordingly.
I've noticed that after I've cracked the nipple undone and he has pressed the pedal down , fluid is displaced into my bleed pipe as expected but then within a few seconds it all disappears back into the wheel cylinder , even with the pedal held down? this is confusing me .
the car is a classic mini with drums all round and front to rear split with a yellow tag master cylinder. everything has been replaced bar the compensator on the bulkhead .
cheers
If fluid is coming out as normal, and steady whilst pedal is being depressed and no air, then close the nipple as this happens. Do not wait until the end.
Or use a pressure/vac bleeder as others suggest. But if you have 2 people it should be easy.
You can get various contraptions designed to stop fluid draining out of the bleed pipe and letting air back in, but the easiest way I've found is to connect a couple of feet of pipe and feed that up into a container that is higher than the caliper. I actually sit the container next to the master cylinder so I can see the state of the fluid coming out from the driver's seat, but it isn't essential for it to be that high. That will solve the worst of the problem. The tiny amount of residual pressure this puts on the system will also prevent it from sucking air in past the threads of the bleed nipple. It's still good practice to close the nipple while the pedal is moving down so the system is under pressure when you finished bleeding to eliminate any chance of sucking air back in.
Since you have replaced major components of the brake system you could easily have air trapped in it. You will need to look at the orientation of the brake lines and components and work out where the air pockets will form, especially in the calipers but also in the bias valve and any pipe runs that include uphill sections.
Since you have replaced major components of the brake system you could easily have air trapped in it. You will need to look at the orientation of the brake lines and components and work out where the air pockets will form, especially in the calipers but also in the bias valve and any pipe runs that include uphill sections.
the car has been sat for quite a few years since my dad passed away, brakes were seized on, wheel cylinders leaking and corroded brake pipes etc, basically it's had all wheel cylinders, brake shoes, various pipes and a new master.
I used a ezebleed to start with, got no visible air in my bleed pipe but had no pedal pressure at all after bleeding, even with pumping the pedal.
tried the up/ down two man method, locking the nipple between strokes.
we bled the cylinder first to make sure it was pushing fluid out, then went onto each wheel cylinder in the correct order.
this was when I noticed the fluid drawing back from my bleed pipe and back into the cylinder, have never had this before, and because of this I can't bleed them via the pedal.
the master is obviously displacing fluid and pushing it out of the nipple but as soon as the pedal cones to rest at the bottom the fluid draws itself back in before I get chance to lock the nipple off .
I used a ezebleed to start with, got no visible air in my bleed pipe but had no pedal pressure at all after bleeding, even with pumping the pedal.
tried the up/ down two man method, locking the nipple between strokes.
we bled the cylinder first to make sure it was pushing fluid out, then went onto each wheel cylinder in the correct order.
this was when I noticed the fluid drawing back from my bleed pipe and back into the cylinder, have never had this before, and because of this I can't bleed them via the pedal.
the master is obviously displacing fluid and pushing it out of the nipple but as soon as the pedal cones to rest at the bottom the fluid draws itself back in before I get chance to lock the nipple off .
If the car has not been moved for some time and the brake pedal has seen full travel on bleeding the chances are that the unused part of the bore has gone rusty and taken out your seals.
If I were you I'd be tempted to price up the master cylinder and replace it. Otherwise you clearly have a major leak elsewhere.
If I were you I'd be tempted to price up the master cylinder and replace it. Otherwise you clearly have a major leak elsewhere.
bruteforce1 said:
I've noticed that after I've cracked the nipple undone and he has pressed the pedal down , fluid is displaced into my bleed pipe as expected but then within a few seconds it all disappears back into the wheel cylinder , even with the pedal held down?
It's what you'd expect.You press the pedal. Fluid flows down.
You hold the pedal down. No more fluid flows.
The fluid in the bleed pipe runs out of the bleed pipe, replaced from the bottom up by air.
It's not "disappearing back up" - it's just running out of the pipe and not being replaced.
Open nip, as the pedal starts to go down. Just as the pedal gets to the bottom of the travel, and fluid stops actively flowing out, close the nipple. Then and only then, pedal up.
TooMany2cvs said:
It's what you'd expect.
You press the pedal. Fluid flows down.
You hold the pedal down. No more fluid flows.
The fluid in the bleed pipe runs out of the bleed pipe, replaced from the bottom up by air.
It's not "disappearing back up" - it's just running out of the pipe and not being replaced.
Open nip, as the pedal starts to go down. Just as the pedal gets to the bottom of the travel, and fluid stops actively flowing out, close the nipple. Then and only then, pedal up.
For once I agree with this.You press the pedal. Fluid flows down.
You hold the pedal down. No more fluid flows.
The fluid in the bleed pipe runs out of the bleed pipe, replaced from the bottom up by air.
It's not "disappearing back up" - it's just running out of the pipe and not being replaced.
Open nip, as the pedal starts to go down. Just as the pedal gets to the bottom of the travel, and fluid stops actively flowing out, close the nipple. Then and only then, pedal up.
In addition to what I said regarding getting into the 'unused' bore area I almost never bleed the brakes from the bottom.
But, if you are having issues with the Eezibleed as well it does sound like your master cylinder is toast. With the Eezibleed you only need 20PSi for it to do the work.
SebringMan said:
But, if you are having issues with the Eezibleed as well it does sound like your master cylinder is toast.
He did say that it's a new master...I've not tried an eezibleed, but I have had less-than-overwhelming-success with a mitivac, to the point that last time I tried it - I gave up and went back to gravity and a borrowed foot.
Seems this chap had the same problem:
https://www.pistonheads.com/gassing/topic.asp?h=0&...
This also worth a read:
http://www.theminiforum.co.uk/forums/topic/119038-...
https://www.pistonheads.com/gassing/topic.asp?h=0&...
This also worth a read:
http://www.theminiforum.co.uk/forums/topic/119038-...
Edited by paintman on Tuesday 11th July 09:13
hi again.
in answer to a few questions, yes it's a new master cylinder, most of the braking system is new.
no leaks etc but no pedal pressure either.
have tried everything I can think of
have previously read those links, have looked at most posts I can find on bleeding brake trouble.
thanks tho
in answer to a few questions, yes it's a new master cylinder, most of the braking system is new.
no leaks etc but no pedal pressure either.
have tried everything I can think of
have previously read those links, have looked at most posts I can find on bleeding brake trouble.
thanks tho
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