hi there, I have a 1982 mini with the front to rear split system, drums rear, disks front, no servo and the master cylinder with inbuilt PDWA. after filling the brake system and bleeding it twice there is still no resistance in the pedal at all. is the master cylinder at fault? no obvious leaks, and I've had a good look round. will one of the minispares refurb kits sort it?
cheers, Tom
No Brake Pedal Feel
Started by
tomgale
, Apr 19 2012 08:52 PM
5 replies to this topic
#2
tiger99
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Posted 19 April 2012 - 10:34 PM
The master cylinder may well be faulty. The fluid will be returning to the reservoir when you press the pedal, which is why it does not seem to be leaking extrenally.
Unless the bores of the main cylinder and the PDWA are in perfect condition, no scoring or corrosion whatsoever, you have sufficient experience, and you have scrupulously clean working conditions, it would be better to fit a new master cylinder.
But before you do anything, adjust the rear brakes up really tight, and bleed it again with a pressure bleeder. It may just be a serious amount of trapped air.
Unless the bores of the main cylinder and the PDWA are in perfect condition, no scoring or corrosion whatsoever, you have sufficient experience, and you have scrupulously clean working conditions, it would be better to fit a new master cylinder.
But before you do anything, adjust the rear brakes up really tight, and bleed it again with a pressure bleeder. It may just be a serious amount of trapped air.
#3
dklawson
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Posted 20 April 2012 - 02:05 AM
Also... have you done any other work to the brake system prior to trying to bleed it?
#4
tomgale
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Posted 20 April 2012 - 08:26 AM
The system has been dry for a few years, car is being rebuilt. I've bled them a couple of times, but I'll try again. New master cylinder? Not sure the budget can stretch to that 
might dissassemble and check the bores first
Thanks for the help, Tom.
might dissassemble and check the bores first Thanks for the help, Tom.
#5
jimnali
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Posted 20 April 2012 - 09:05 AM
Is the system fully bled? I had difficulty bleeding my mini's brakes. Eventually I had to work around the car opening every junction to encourage the fluid to flow. Might be worth investing in an Eazybleed?
Are the rear brakes fully adjusted?
A refurb kit might help but you might find difficulty in finding the right one. The master cylinder in my 82 mini is no longer available and I had to replace it with a newer type.
Are the rear brakes fully adjusted?
A refurb kit might help but you might find difficulty in finding the right one. The master cylinder in my 82 mini is no longer available and I had to replace it with a newer type.
#6
dklawson
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Posted 20 April 2012 - 12:17 PM
By "dry" do you literally mean that no fluid was in the system? If so, there are some steps you can take to move this along.
Fill the reservoir and attach a clear hose to the furthest bleed nipple from the master cylinder. Open the bleed nipple about 1/2 turn and put the end of the tubing in a catch jar. Go away for 15 or more minutes. Come back and check if fluid is moving out of the tube and if necessary top up the reservoir. Leave the tube on the open bleed nipple until an ounce or two of fluid has passed through the tubing into the jar. Then close the bleed nipple and move your setup to the next furthest nipple. Repeat this 'gravity bleed' until you have gone all the way around the car.
When that has been done, go through a "normal" bleed process. I only use one method, 2-person. You connect the hose to the bleed nipple and place the other end in the catch jar. You open the nipple 1/2 turn and call "down" to your assistant. They push the brake pedal SLOWLY to the floor and hold it down. When the pedal is down they call "down" back to you and you close the bleed nipple. Once closed you call "release" to tell your assistant to let the pedal return to the top. When the pedal is at the top they call "up" back to you. You repeat this process until no bubbles are seen coming out of the tubing. Make sure to check the reservoir frequently and top it up as needed. This is the method typically used to completely flush the hydraulic system.
All that being said, make sure if the front calipers have been serviced that their bleed nipples are at the "top". Sometimes people get confused and install the calipers on the wrong side with the nipples "down". The system cannot bleed with the nipples down.
Another area of concern as mentioned above is that the drum brakes need to be properly adjusted before bleeding the brakes. In addition to the adjustment, if you have replaced the brake shoes, it is imperative that the shoes are placed in the correct position. You will note the friction material does not cover all of the curved metal backer plate, it is relieved at one end. The relieved end of the shoe goes at the "top" on the front shoe, and the "bottom" of the rear shoe for both left and right sides of the car. If the shoes are on the wrong way, you can have a very very soft brake pedal no matter how much you bleed the brakes or try to adjust them.
Fill the reservoir and attach a clear hose to the furthest bleed nipple from the master cylinder. Open the bleed nipple about 1/2 turn and put the end of the tubing in a catch jar. Go away for 15 or more minutes. Come back and check if fluid is moving out of the tube and if necessary top up the reservoir. Leave the tube on the open bleed nipple until an ounce or two of fluid has passed through the tubing into the jar. Then close the bleed nipple and move your setup to the next furthest nipple. Repeat this 'gravity bleed' until you have gone all the way around the car.
When that has been done, go through a "normal" bleed process. I only use one method, 2-person. You connect the hose to the bleed nipple and place the other end in the catch jar. You open the nipple 1/2 turn and call "down" to your assistant. They push the brake pedal SLOWLY to the floor and hold it down. When the pedal is down they call "down" back to you and you close the bleed nipple. Once closed you call "release" to tell your assistant to let the pedal return to the top. When the pedal is at the top they call "up" back to you. You repeat this process until no bubbles are seen coming out of the tubing. Make sure to check the reservoir frequently and top it up as needed. This is the method typically used to completely flush the hydraulic system.
All that being said, make sure if the front calipers have been serviced that their bleed nipples are at the "top". Sometimes people get confused and install the calipers on the wrong side with the nipples "down". The system cannot bleed with the nipples down.
Another area of concern as mentioned above is that the drum brakes need to be properly adjusted before bleeding the brakes. In addition to the adjustment, if you have replaced the brake shoes, it is imperative that the shoes are placed in the correct position. You will note the friction material does not cover all of the curved metal backer plate, it is relieved at one end. The relieved end of the shoe goes at the "top" on the front shoe, and the "bottom" of the rear shoe for both left and right sides of the car. If the shoes are on the wrong way, you can have a very very soft brake pedal no matter how much you bleed the brakes or try to adjust them.
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