i have just replaced rear pads on 147. pistons wound in ok never cracked bleed nipple just took her out on road test the pedal is very light for the 1st half with no brake effort at all then it will start to slow but not very good at all. any ideas what could be wrong?
brake pedal goes to floor after changing rear pads
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G
Guest
·First of all... What type of brake pads did you fit... Performance or standard type?
Did you replace just the pads or did you replace the discs to?
It has a bearing on how you treat them to bed them in...
With normal road type pads, unusual spongy feeling is totally normal when bedding brakes in and should be done properly and with time and care.
Simply stamping on them and expecting them to work is simply NOT an option. It can take up to 200 miles+ of steady driving and steady braking during that time.... Imagine the brake disc is like a mountain range, your brake pads are flat so when they come in contact, they are only making that contact on the peaks of the mountains... Normal wear will bring the surface area contact closer together as the surface area increases.
If you can't wait that long.....
On a safe quiet road.....Take the car up to speeds of 40 mph and brake with a medium pedal force then gently & slowly release the brake once the car is below 15mph until the car slows to prevent heat soak... Let it cool for a minute or two and repeat the process....
If things are improving, increase the starting speed gradually but keeping the brake pedal release speed the same.
The last 15mph of braking is where the most heat transfers through the pads so thats why you gently release the pedal.
Damage with heat soak can occur to the pads if left against the discs after heavy braking, they will start to crumble, so give them time to cool.
It usually takes about twenty minutes to get pads close to normal with this process so be patient
If it is just the same with no improvement:
Look for other faults
Did you remove the brake fluid reservior cap when winding the pistons back?
It's a simple thing that many people don't do or forget about.
When winding the pistons back the system is under a lot more back pressure compression than normal. The extra pressure on the system can find that brake fluid can leak in past the piston seals!
If fluid can leak past, air can replace it!......... So give the brake system a quick bleed on all four calipers.
What condition were the old pads in? Wasthere still enough "meat" on them, If so it could be an underlying problem with the caliper sliding pins so the caliper is only braking on one side. Take out the pins , clean them up with emerycloth and a light coating of copper grease does the job mate.
Hope this helps mate.....
Did you get an advice note with the pads? Usually they put them in the box with bedding in instructions:thumbs:
Did you replace just the pads or did you replace the discs to?
It has a bearing on how you treat them to bed them in...
With normal road type pads, unusual spongy feeling is totally normal when bedding brakes in and should be done properly and with time and care.
Simply stamping on them and expecting them to work is simply NOT an option. It can take up to 200 miles+ of steady driving and steady braking during that time.... Imagine the brake disc is like a mountain range, your brake pads are flat so when they come in contact, they are only making that contact on the peaks of the mountains... Normal wear will bring the surface area contact closer together as the surface area increases.
If you can't wait that long.....
On a safe quiet road.....Take the car up to speeds of 40 mph and brake with a medium pedal force then gently & slowly release the brake once the car is below 15mph until the car slows to prevent heat soak... Let it cool for a minute or two and repeat the process....
If things are improving, increase the starting speed gradually but keeping the brake pedal release speed the same.
The last 15mph of braking is where the most heat transfers through the pads so thats why you gently release the pedal.
Damage with heat soak can occur to the pads if left against the discs after heavy braking, they will start to crumble, so give them time to cool.
It usually takes about twenty minutes to get pads close to normal with this process so be patient
If it is just the same with no improvement:
Look for other faults
Did you remove the brake fluid reservior cap when winding the pistons back?
It's a simple thing that many people don't do or forget about.
When winding the pistons back the system is under a lot more back pressure compression than normal. The extra pressure on the system can find that brake fluid can leak in past the piston seals!
If fluid can leak past, air can replace it!......... So give the brake system a quick bleed on all four calipers.
What condition were the old pads in? Wasthere still enough "meat" on them, If so it could be an underlying problem with the caliper sliding pins so the caliper is only braking on one side. Take out the pins , clean them up with emerycloth and a light coating of copper grease does the job mate.
Hope this helps mate.....
Did you get an advice note with the pads? Usually they put them in the box with bedding in instructions:thumbs:
Joined
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8,480 Posts
Sounds like the brakes haven't been adjusted properly - to do that, just operate the handbrake a few times until it goes back to normal.
Joined
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5,268 Posts
What Dave said.
the front brakes arnt working to. it hardly stopped, ive just got in from work and tried pedal and went straight to the floor with a funny noise maybe from master cylinder im thinking the seal has popped over in there? ive pumped pedal until it went hard and jammed it down with sum wood, see if that pops seal the right way round? if not il have a go at bleeding brakes before work tomorrow. thanks for replies i will try and work hand brake on and off first tho. 
Joined
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9,913 Posts
sorry i beg to differ there ........... you pump brake up with foot pedal not handbrake:tut:
Joined
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9,913 Posts
it seems that to me youve wound pistons right out and when you press pedal its taking up play in piston but not enough for contact with disc but when you release footbrake instead of calipers adjusting they are going back to original position ,so seems to me your internal adjusters in calipers are not working but sticking
Joined
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5,268 Posts
Nope, you reset the rear brakes anyhow by using the handbrake a number of times, this winds the pistons back out till the pads are touching the disks.
Joined
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9,952 Posts
I'm with DaveAlfa on this...correct procedure is to slacken handbrake cable at the lever end, pump out the pisons using the footbrake, then adjust cable at lever end to get the correct movement - say 3 "clicks"....
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