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Bleeding The Master Brake Cylinder

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#1 leeesslemont

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Posted 12 September 2019 - 01:22 PM

Hi

 

Ive replaced the callipers, shoes, hoses and some pipes on my 1998 MPI.  Now I believe that I have to bleed the Master Brake Cylinder before bleeding each of the 4 corners. 

 

What equipment should I use bleeding the cylinder?  i.e. what fittings to folks use for attaching plastic pipe into the Master Cylinder ports? Any info / links would be much appreciated. 

 

Do I even need to bleed the Master Cylinder or can air from here be expelled through the bleeding of each corner? 

 

All advice / guidance much appreciated. 

 

Cheers

Lee

 

 



#2 cal844

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Posted 12 September 2019 - 02:51 PM

The air from the master cylinder will make it's way to each corner. I usually leave the unions at the master cylinder loose until fluid weeps from them. I then tighten and open the bleed nipples on each corner of the car and pump like crazy, just to get the fluid moving.

Bleed furthest away from the master first, so for a RHD car it will be

Rear left
Rear right
Front left
Front right

A bit of a dance, I know but that's how I've always done minis. I also find that two man bleeding is better than vacuum bleeding, pressure bleeding is a last resort.

Hope this helps

#3 leeesslemont

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Posted 12 September 2019 - 03:10 PM

Thanks for the advise. 

 

Just so I've got this right, Undo the unions at the master cylinder until fluid weeps then tighten up and bleed each corner as normal. 

 

:D



#4 richmondclassicsnorthwales

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Posted 12 September 2019 - 03:54 PM

Yes- just as cal844 says

 

After the first attempt - don't be surprised if you have to do another round of dancing with your Mini to get the pedal a bit firmer



#5 cal844

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Posted 12 September 2019 - 04:11 PM

Thanks for the advise.

Just so I've got this right, Undo the unions at the master cylinder until fluid weeps then tighten up and bleed each corner as normal.

:D


Yes mate that's correct, you may find if you have the bulkhead mounted proportioning valve (FAMwtf valve) that you need to loosen the unions on the bottom of the valve as air gets trapped there too.

#6 leeesslemont

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Posted 12 September 2019 - 07:16 PM

Thanks for the advise.

Just so I've got this right, Undo the unions at the master cylinder until fluid weeps then tighten up and bleed each corner as normal.

:D

Yes mate that's correct, you may find if you have the bulkhead mounted proportioning valve (FAMwtf valve) that you need to loosen the unions on the bottom of the valve as air gets trapped there too.


#7 leeesslemont

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Posted 12 September 2019 - 07:39 PM

At the risk of asking a stupid question, where will I find the bulkhead mounted proportioning valve (FAMwtf valve)?

I’ve had a look in the Haynes manual but not sure?

#8 cal844

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Posted 12 September 2019 - 08:07 PM

At the risk of asking a stupid question, where will I find the bulkhead mounted proportioning valve (FAMwtf valve)?

I’ve had a look in the Haynes manual but not sure?



They're usually on the end of the bulkhead cross member.

It depends on the age of the car, any from 76 onwards should have one fitted.

If you trace the front brake pipe back to the master cylinder you will find it.

If you need images you can just Google search classic mini brake pressure regulator

Or part number FAM7821

#9 cal844

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Posted 12 September 2019 - 08:12 PM

Fam7821 https://imgur.com/gallery/uh1Wmlt

This is a picture from a thread on this forum

Edited by cal844, 12 September 2019 - 08:13 PM.


#10 leeesslemont

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Posted 12 September 2019 - 08:23 PM

Ok cheers.........found it now

Thanks for your help. Much appreciated!

#11 cal844

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Posted 12 September 2019 - 08:55 PM

No problem, I try my best to help!

Keep us posted with how you get on

#12 richmondclassicsnorthwales

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Posted 12 September 2019 - 09:08 PM

These valves are a pain in the arse, you can.t tell if they work or not, and at £90 a pop, not cheap, and you can't repair the either



#13 leeesslemont

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Posted 13 September 2019 - 01:46 PM

Update........

 

First attempt at Bleeding. Let the master cylinder weep, then tightened up.  

Bled each of the 4 corners until no bubbles, clean fluid only coming out. 

 

Conclusion, only been able to test on drive, car does stop but I there is still a lot of air in the system.  Pedal is very spongy and has to travel all the way to the bottom. 

 

so, next steps.  Crack the FAM valve?  Do another round of bleeding each corner? 



#14 MiniMadRacer

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Posted 13 September 2019 - 01:51 PM

When bleeding I like to have two of us at it.... I get a friend to pump the brake pedal like crazy until it gets hard (STOP IT YOU LOT)  then with him keeping his foot hard on the brake I crack of one nipple to bleed it... I repeat this process as often as needed on each wheel..



#15 cal844

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Posted 13 September 2019 - 09:28 PM

When bleeding I like to have two of us at it.... I get a friend to pump the brake pedal like crazy until it gets hard (STOP IT YOU LOT) then with him keeping his foot hard on the brake I crack of one nipple to bleed it... I repeat this process as often as needed on each wheel..


That is a messy way but it will work, just be sure to have a small hose to take the fluid away from the wheel





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