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I hate brake jobs!!! Help me
https://www.ausmini.com/forums/viewtopic.php?f=2&t=79742		 Page 1 of 1
Author:  estapol [ Mon Dec 31, 2012 11:29 am ]
Post subject:  I hate brake jobs!!! Help me
Hey all,

Right!
I have to get the braking system working for car removal.
It all looks good, all the lines are in and tight and the master cylinder is in there
(single circuit system btw).
When I put brake fluid in the reservoir and pump its just a slack pedal, even after 20,000 pumps. And yes the pedal is connected to the cylinder.

So I pulled off the master cylinder and rebuilt it.... no avail still not pumping fluid..... If I put the pipe coming off the cylinder in a bottle of fluid and pump it, it pulls and pushes fluid!!!I don't understand whats wrong with it? Probably something retardly simple.

What should I do???

Thinking there might be a block in the reservoir to cylinder hole or something??

Thanks in advance
Hoba
Author:  Mike_Byron [ Mon Dec 31, 2012 12:02 pm ]
Post subject: 
You probably have numerous air locks. You cant actually do any bleeding until you have pressurisation in the lines.

There are two ways to handle this. The first is to open all the bleed nipples on the wheels. Stick a tin under each nipple so you dont have a big mess and just let gravity do its job until you have fluid in each line all the way to the bleed nipples. May take 24 hours or more though. The you bleed in the normal way.

Or

You can bleed in stages. Make the master cylinder is pumping firstly by cracking the pipe connection at the top of the master cylinder. Then again at the junction where the pipes separate and then repeat until you get to the wheel cylinders bleed nipples.

The correct way is to back off the brake adjustment. Bleed the passenger wheel first, the the drivers rear wheel, the the passenger front and the drivers front is last.

Just remember that brake fluid is viscous and takes a second or two to fill in the master cylinder so pump the pedal slowly and pause at the top of the stroke and at the bottom. Pumping furiously and quickly just frothes up the brake fluid.

See how you go

Mike
Author:  peterb [ Mon Dec 31, 2012 4:11 pm ]
Post subject: 
If it's pushing fluid back and forth, it could be blocked in tiny holes into cylinder from resivour, the ones in piston or assembled wrong. Try puting 3/8" unf bolt in where pipe goes, then try pedal, should be rock solid. if it isn't, fault's in m/c, if it is then it's air in rest of system.
Author:  MattE [ Mon Dec 31, 2012 8:05 pm ]
Post subject: 
Thanks to advice recieved on ausmini, I've had good success recently with gravity bleeding initially, then (if you can), letting the system rest for a day or so before bleeding normally. I like to have my assistant apply pedal pressure, to let the fluid that is draining drop the pedal to the floor. Close off the nipple before repeating (slow pedal operation like Mike said) on each of the other corners. After that (time permitting), you might like to repeat after a day or so. I think air bubbles work their way up through the master cylinder, or down to the calipers/wheel cylinders.

Another thing I was taught once was the idea of bleeding a new (read: dry) m/cyl on the workbench. Not sure how applicable it is to the simple mini system though.

One thing seems certain in all of this though - pumping the life out of it is no good for a master cylinder, and you are probably just creating teeny tiny bubbles which will never bleed out!

One other thing to mention is that an incorrectly built (or rebuilt) master cylinder can wreck everything. In my case, a ring in piston from some other assembly blocked the compensating port, so was never going to work properly.

Here's a pic - I forget which one was the correct one.
Image

Good luck.
Author:  Timbo [ Mon Dec 31, 2012 9:14 pm ]
Post subject: 
MattE wrote:
...Another thing I was taught once was the idea of bleeding a new (read: dry) m/cyl on the workbench. Not sure how applicable it is to the simple mini system though...


I recently bought a Gunson Eezibleed and the instructions in it explicitly said that if you have an early mini, bleed the master cylinder seperately before connecting it to the rest of the system. I installed it into the car and bled it before connecting it to the brake line and everything worked perfectly.

Tim
Author:  peterb [ Tue Jan 01, 2013 7:06 am ]
Post subject: 
Another trick is to fill system and then "carefully", apply some pressure to the resivior via compressed air or bike pump, sort of pressure bleeder. On the old tin cylinders, this wasnt too hard, couple of bits of hose etc, the newer plastic ones it's a bit trickier. You don't need much, a few PSI, in old school terms. That's probably 25,000,000 hectogigles in metric. It's just to create 'flow' through pipes, pushing fluid through and air out. DON'T let cylinder run out, you'll be bach at square one.
You can also vacume bleed them, Supercheap/Repco sell units but they cost, unless a mate might have one.

http://www.jhmbuttco.com/acatalog/Shop_ ... rs_37.html
Author:  estapol [ Tue Jan 08, 2013 1:37 pm ]
Post subject: 
Quote:
if you have an early mini, bleed the master cylinder seperately before connecting it to the rest of the system


Thanks this worked well,
Still got airlocks but at least the pedal is hardening slowly :)
Will keep pressing away with it.
Author:  timmy201 [ Tue Jan 08, 2013 1:53 pm ]
Post subject: 
I had a similar problem on my last car.

First fault was that one of the brake pads fell out a little bit!

Second problem was that although I'd unscrewed the bleeder, the ball bearing that closes the valve had jammed closed. I found this out only as it shot across the garage floor after an especially hard pump on the brakes...
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