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Brake Bleeding Issue

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#1 blacktulip


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Posted 29 June 2020 - 09:33 AM

I took my master cylinder off my 69 cooper (no servo) to spruce the bay up and now I have refitted it I have tried to bleed the system through. The passenger rear lets fluid through but the front calipers and drivers rear let nothing through. The nipples open but the pedal is not pushing through. The pedal feels like it does when everything is normal and running. I initially wondered if the master was seized so I tried the passenger rear again as that one let the fluid through and it did push through so it's not a seized master. Has anyone ever seen this happen? Can the lines block up?

Edited by blacktulip, 29 June 2020 - 09:36 AM.

#2 cal844


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Posted 29 June 2020 - 10:44 AM

Are the calipers on the correct side? (Nipple to the top)

For brake bleeding I use the two man method, one pumps the pedal and checks fluid level, the other does the unions and nipples.

You need to chase the air from the master cylinder to the slave cylinders and calipers.

Crack the MC union that is giving problems (you may need to wind out a couple of turns, if the pedal is stiff)

pump the pedal until fluid comes out between the union and pipe.

Nip up that union so the fluid stops between the pipe union.

Repeat this along the line, especially past the FAMwtf valve on the bulkhead (if fitted, I think your car may be too early for that system.)
Personally I wouldnt disturb the flexible lines, just proceed straight to the cylinder or caliper nipple.

You want to leave the nipple open (whilst doing the above) ideally use a piece of hose from the nipple end into a jar of clean fluid so you can see the air escaping.(once you have fluid along the full system.)

What I then do at this stage is stop, make sure there are no leaks further back the system then get your assistant to give 5 full stroke pumps of the pedal and hold it fully down. You then close the nipple and release the pedal.

Bleed order that I use is
Nsr passenger rear
Osr drivers rear
NSF passenger front
Osf drivers front

If you are struggling to get a pedal you can clamp all flex lines, checking the pedal once you have each clamp fitted to see where the air is.
If you clamp one and the pedal is still soft or long you need to bleed that corner more.

A long winded post but I've tried to include all I can think of.

Any issues dont hesitate to report back!



#3 mkw


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Posted 29 June 2020 - 11:53 AM

Gunsons Eazibleed may help, force the fluding down the line and out under a constant pressure

#4 sonscar


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Posted 29 June 2020 - 04:46 PM

Are both rear brakes teed on the same circuit,if one bleeds so should the other?Steve.

#5 blacktulip


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Posted 29 June 2020 - 05:56 PM

Hi guys, sorry if I haven't explained myself properly. The nipples are free and not siezed but the pedal won't push down. The pedal feels like the brakes are as normal I.e bled and ready to drive even when the nipples are open. I will jack all 4 corners up and see if the calipers and rears lock up when pressed.

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