Mushy brake pedal feel after brake pad replacement.
05-05-2017, 11:11 AM
#51
Super Moderator
So, I had the over return problem and fixed it with the suggestions in the thread. I thought I was all good but then after about 5 KM of driving I started to notice a noise. It sounded like a low hum, possibly a vibration. Most of the time it goes away when I step on the brake. So I took apart the front driver side again, cleaned everything up even more, drove the piston out and back in again, put it all back together and still the same thing. I did notice after the first "adjustment" of the piston and a bit of driving, that I could still see at least a milimeter of space between the rotor and pad which struck me as odd. It's almost like the pad is slightly binding (although I'm not sure how). I'm at the point now where I'm thinking of getting some new seals and "rebuilding" the caliper as I'm speculating the over return problem is still there and there's enough space for the pad to move slightly ajar and then vibrate off of the rotor.
Would appreciate it if anyone had any ideas
Would appreciate it if anyone had any ideas
05-06-2017, 04:48 PM
#52
MBWorld Fanatic!
I'm curious if these problems are related to many drivers in this thread driving their car after replacing the pad only and not the rotors?
05-06-2017, 09:40 PM
#53
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sbainb (01-21-2019)
01-21-2019, 08:59 PM
#57
Super Moderator
Delighted we were able to help! This issue can occur with any vehicle with disc brakes. Some don't even realise they are suffering from the condition unless it's severe. They learn to live with it unless chronic.
05-04-2019, 07:53 AM
#58
MBWorld Fanatic!
I just finished upgrading to 6/4 pot calipers and I experienced this caliper over return condition first hand; when I create a thread for it in the W209 forum I'm going to link this thread as well so more people are aware of this issue. I'm really glad Glyn took the time to describe the problem and explain how to fix it. The only thing I want to add is to make sure the caliper is really tight on the rotors, for me the brakes were 90% good after I did that; then over the next two weeks the calipers must have adjusted further because they feel 100% now.
05-05-2019, 05:32 PM
#59
Super Member
How thick must the spacer block be you insert to push pistons out but not out of the bore-?
How does the factory do this installation, do they use a jig to overcome this problem, and if so how does it looK and measure-?
How does the factory do this installation, do they use a jig to overcome this problem, and if so how does it looK and measure-?
Last edited by Moto_Guzzi; 05-07-2019 at 11:32 AM.
05-07-2019, 09:46 AM
#60
MBWorld Fanatic!
Very interesting thread .... I've done many pad changes and replacements over the years on my Japanese cars and Porsches and never encountered this. Perhaps compressing the pistons only enough to get the new pads in place helped, not sure. Good to know for the first time I do my Mercedes.
08-25-2019, 07:04 PM
#61
Senior Member
Glyn, thank you so much for posting this. I have, for the last 40 or so years, been doing my own brakes, in fact all maintenance on all our cars, Ferrari engine out, etc. I have been driving myself nuts dealing with a low brake pedal on our ML350 BT. Bleeding, bleeding, bought new pads, ready to change out even though the others were 3/4 new! Found your thread, and thought, what have I got to lose... and followed it. Thanks again for the education, brakes are solid,/firm and responsive and no mushy feeling... would have never guessed, Master cyl would have been in the near future. Even used the older(1/4 used) pads and returned the new ones. Happy Camper....AAAAAA++++! I wonder how many others have experienced this pain?
Hope you don't mind but I'll be posting this thread to the 166(ML) section in hopes that it may help someone there...
thanks again,
Sandy
Hope you don't mind but I'll be posting this thread to the 166(ML) section in hopes that it may help someone there...
thanks again,
Sandy
Last edited by Koenig1; 08-25-2019 at 07:12 PM.
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Glyn M Ruck (08-25-2019)
10-20-2019, 12:25 AM
#63
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2011 E350 Standard
Brake pad replacement
See pad break-in procedure on the Stoptech website.
This is a common problem with 2 main causes - Calipers over returning or changing the front pads without doing the rears. So tell us - did you change all the pads? If not - do so & then do the break-in procedure
The pistons in a brake caliper depend on the distortion of the D shaped seal to return them to the brakes off or resting position. When changing pads on these cars great care should be taken not to push the pistons back too far in the caliper to get the old pads out. You should just push them back sufficiently to release the old pads. If you don't do this, stiction of seals on the caliper bore can cause the piston to move forward but not bring the seal with it down the bore surface & cause the piston to over return when you release the brakes. You then need more fluid to bring the pads back in contact with the disc (rotor) which gives you a low or mushy pedal.
There are two ways to fix this - one laborious & the other risks popping the pistons out of the calipers so be carefull.
If replacing all pads does not fix the problem - then you need to remove all pads. Make up some wooden or similar spacers about the thickness of a brake pad backing plate. Insert these or old backing plates with no friction material on them into the calipers & stomp on the brakes to move ALL the pistons forward in their bores. Then push back gently until you can just slip the new pad in & you should should have cured the over return.
The alternative is to strip & dry all fluid out of the braking system. Reassemble the calipers with pads, shims, pins & all. Blow the pads against the discs with compressed air & then bleed the braking system.
Good luck - I hope your problem is just not replacing all the pads at the same time.
This is a common problem with 2 main causes - Calipers over returning or changing the front pads without doing the rears. So tell us - did you change all the pads? If not - do so & then do the break-in procedure
The pistons in a brake caliper depend on the distortion of the D shaped seal to return them to the brakes off or resting position. When changing pads on these cars great care should be taken not to push the pistons back too far in the caliper to get the old pads out. You should just push them back sufficiently to release the old pads. If you don't do this, stiction of seals on the caliper bore can cause the piston to move forward but not bring the seal with it down the bore surface & cause the piston to over return when you release the brakes. You then need more fluid to bring the pads back in contact with the disc (rotor) which gives you a low or mushy pedal.
There are two ways to fix this - one laborious & the other risks popping the pistons out of the calipers so be carefull.
If replacing all pads does not fix the problem - then you need to remove all pads. Make up some wooden or similar spacers about the thickness of a brake pad backing plate. Insert these or old backing plates with no friction material on them into the calipers & stomp on the brakes to move ALL the pistons forward in their bores. Then push back gently until you can just slip the new pad in & you should should have cured the over return.
The alternative is to strip & dry all fluid out of the braking system. Reassemble the calipers with pads, shims, pins & all. Blow the pads against the discs with compressed air & then bleed the braking system.
Good luck - I hope your problem is just not replacing all the pads at the same time.
In your reply you say to make some shims about the thickness of the backing plate on all calipers and mash brakes until pistons are at full travel in bore... Don’t you mean against the rotor? If you just use the thickness of the backer plate (about 1/4”) the piston will surely blow out. I’m assuming you mean put the caliper back in place against the rotor to simulate brake pad completely wore down??? I’ve done brakes hundreds of times and have never encountered this. I compressed the pistons just barely enough to get unit to go back on. Bleeding the brakes didn’t work either. Thanks
Last edited by Glyn M Ruck; 10-20-2019 at 10:11 AM.
10-20-2019, 10:12 AM
#64
Super Moderator
I said. "Make up some wooden or similar spacers about the thickness of a brake pad backing plate. Insert these or old backing plates with no friction material on them into the calipers & stomp on the brakes to move ALL the pistons forward in their bores."
Yes obviously with the spacer hard up against the rotors/discs.
Good luck!
Yes obviously with the spacer hard up against the rotors/discs.
Good luck!
Last edited by Glyn M Ruck; 10-20-2019 at 10:14 AM.
10-20-2019, 02:06 PM
#65
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2011 E350 Standard
I said. "Make up some wooden or similar spacers about the thickness of a brake pad backing plate. Insert these or old backing plates with no friction material on them into the calipers & stomp on the brakes to move ALL the pistons forward in their bores."
Yes obviously with the spacer hard up against the rotors/discs.
Good luck!
Yes obviously with the spacer hard up against the rotors/discs.
Good luck!
Kind regards,
04-25-2020, 03:14 PM
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2013 C300 4Matic
Hello all,
I just joined this forum just so I could post to this old thread, because my 2013 C300 4Matic seems to have the notorious caliper over return issue after I changed the front rotors and pads yesterday before I stumbled across this thread, so I did the change the old school way by pushing the pistons back into their bores as far as they would go. I did the rears this time last year, and the car is lightly used, so the rear pads are almost new and I hope the differential fluid volume issue Glyn talks about above doesn't apply to me. So I did an abridged version of Glyn's fix - only the fronts - and I must be the unlucky guy in the group because sadly it made absolutely no difference - still a very mushy brake pedal. Now I'm wondering what to do next. Any ideas?
Tom
I just joined this forum just so I could post to this old thread, because my 2013 C300 4Matic seems to have the notorious caliper over return issue after I changed the front rotors and pads yesterday before I stumbled across this thread, so I did the change the old school way by pushing the pistons back into their bores as far as they would go. I did the rears this time last year, and the car is lightly used, so the rear pads are almost new and I hope the differential fluid volume issue Glyn talks about above doesn't apply to me. So I did an abridged version of Glyn's fix - only the fronts - and I must be the unlucky guy in the group because sadly it made absolutely no difference - still a very mushy brake pedal. Now I'm wondering what to do next. Any ideas?
Tom
Last edited by benzineer; 04-25-2020 at 03:16 PM. Reason: To be more specific
05-03-2020, 09:13 AM
#68
Super Moderator
Redo the whole process both back & front. Then bleed from longest line to shortest line. It is the only way. You need to get ALL caliper pistons forward & the push them back so that you can just insert the pad at all locations.
Good luck.
Good luck.
07-24-2021, 10:28 PM
#69
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2005 CLK320 W209
Wow! Just to change front pads, I have to take all wheels off, remove all calipers and push all calipers pistons out by pressing the break, then manually push back the position just far enough so it can seat on the pad... all simultaneously or can I do one at a time? Question for Glyn, what does bleed from longest line to shortest line mean?
Sorry for posting on an old thread..
thanks
R
Sorry for posting on an old thread..
thanks
R
07-25-2021, 03:09 AM
#70
Senior Member
No definitely don't do that.
Just change the pads as normal, I have read this and very sorry to say I put no faith what so ever in the mentioned process, if it works for you great.
This comes from years and years of experience across all all types of cars changing all types of combinations front, rear, pads shoes drums and discs etc.
The purpose of the square calliper piston seal is to 1- seal the piston fluid in/dirt out, 2 to distort slightly when brake is applied so when brake is released the piston is drawn back slightly in to the calliper thus removing the disc pad from contacting the disc provide an air gap.
With a new seal the calliper piston moves back the most, with a well used aged seal the piston does not move back very far which can be felt if trying to spin the wheel while the vehicle is jacked up there is brake drag from the pads gently touching the disc.
If the front pads/brakes are worn out replace those there is no need to replace the rears unless you they are worn out also.
I would recommend bleed the brakes at the same time, and yes the brake will be soft for a week or two until the pads and discs have 100% surface contact and no- roaring up the road and stomping on the brakes will not fix this.
Just change the pads as normal, I have read this and very sorry to say I put no faith what so ever in the mentioned process, if it works for you great.
This comes from years and years of experience across all all types of cars changing all types of combinations front, rear, pads shoes drums and discs etc.
The purpose of the square calliper piston seal is to 1- seal the piston fluid in/dirt out, 2 to distort slightly when brake is applied so when brake is released the piston is drawn back slightly in to the calliper thus removing the disc pad from contacting the disc provide an air gap.
With a new seal the calliper piston moves back the most, with a well used aged seal the piston does not move back very far which can be felt if trying to spin the wheel while the vehicle is jacked up there is brake drag from the pads gently touching the disc.
If the front pads/brakes are worn out replace those there is no need to replace the rears unless you they are worn out also.
I would recommend bleed the brakes at the same time, and yes the brake will be soft for a week or two until the pads and discs have 100% surface contact and no- roaring up the road and stomping on the brakes will not fix this.
Last edited by NZ-Merc; 07-25-2021 at 03:17 AM.
07-31-2021, 01:08 AM
#71
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2005 CLK320 W209
No definitely don't do that.
Just change the pads as normal, I have read this and very sorry to say I put no faith what so ever in the mentioned process, if it works for you great.
This comes from years and years of experience across all all types of cars changing all types of combinations front, rear, pads shoes drums and discs etc.
The purpose of the square calliper piston seal is to 1- seal the piston fluid in/dirt out, 2 to distort slightly when brake is applied so when brake is released the piston is drawn back slightly in to the calliper thus removing the disc pad from contacting the disc provide an air gap.
With a new seal the calliper piston moves back the most, with a well used aged seal the piston does not move back very far which can be felt if trying to spin the wheel while the vehicle is jacked up there is brake drag from the pads gently touching the disc.
If the front pads/brakes are worn out replace those there is no need to replace the rears unless you they are worn out also.
I would recommend bleed the brakes at the same time, and yes the brake will be soft for a week or two until the pads and discs have 100% surface contact and no- roaring up the road and stomping on the brakes will not fix this.
Just change the pads as normal, I have read this and very sorry to say I put no faith what so ever in the mentioned process, if it works for you great.
This comes from years and years of experience across all all types of cars changing all types of combinations front, rear, pads shoes drums and discs etc.
The purpose of the square calliper piston seal is to 1- seal the piston fluid in/dirt out, 2 to distort slightly when brake is applied so when brake is released the piston is drawn back slightly in to the calliper thus removing the disc pad from contacting the disc provide an air gap.
With a new seal the calliper piston moves back the most, with a well used aged seal the piston does not move back very far which can be felt if trying to spin the wheel while the vehicle is jacked up there is brake drag from the pads gently touching the disc.
If the front pads/brakes are worn out replace those there is no need to replace the rears unless you they are worn out also.
I would recommend bleed the brakes at the same time, and yes the brake will be soft for a week or two until the pads and discs have 100% surface contact and no- roaring up the road and stomping on the brakes will not fix this.
12-18-2023, 12:55 AM
#72
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03 7.3 f250, 03 s10 blazer xtreme, 84 5.3 swapped iroc
See pad break-in procedure on the Stoptech website.
This is a common problem with 2 main causes - Calipers over returning or changing the front pads without doing the rears. So tell us - did you change all the pads? If not - do so & then do the break-in procedure
The pistons in a brake caliper depend on the distortion of the D shaped seal to return them to the brakes off or resting position. When changing pads on these cars great care should be taken not to push the pistons back too far in the caliper to get the old pads out. You should just push them back sufficiently to release the old pads. If you don't do this, stiction of seals on the caliper bore can cause the piston to move forward but not bring the seal with it down the bore surface & cause the piston to over return when you release the brakes. You then need more fluid to bring the pads back in contact with the disc (rotor) which gives you a low or mushy pedal.
There are two ways to fix this - one laborious & the other risks popping the pistons out of the calipers so be carefull.
If replacing all pads does not fix the problem - then you need to remove all pads. Make up some wooden or similar spacers about the thickness of a brake pad backing plate. Insert these or old backing plates with no friction material on them into the calipers & stomp on the brakes to move ALL the pistons forward in their bores. Then push back gently until you can just slip the new pad in & you should should have cured the over return.
The alternative is to strip & dry all fluid out of the braking system. Reassemble the calipers with pads, shims, pins & all. Blow the pads against the discs with compressed air & then bleed the braking system.
Good luck - I hope your problem is just not replacing all the pads at the same time.
This is a common problem with 2 main causes - Calipers over returning or changing the front pads without doing the rears. So tell us - did you change all the pads? If not - do so & then do the break-in procedure
The pistons in a brake caliper depend on the distortion of the D shaped seal to return them to the brakes off or resting position. When changing pads on these cars great care should be taken not to push the pistons back too far in the caliper to get the old pads out. You should just push them back sufficiently to release the old pads. If you don't do this, stiction of seals on the caliper bore can cause the piston to move forward but not bring the seal with it down the bore surface & cause the piston to over return when you release the brakes. You then need more fluid to bring the pads back in contact with the disc (rotor) which gives you a low or mushy pedal.
There are two ways to fix this - one laborious & the other risks popping the pistons out of the calipers so be carefull.
If replacing all pads does not fix the problem - then you need to remove all pads. Make up some wooden or similar spacers about the thickness of a brake pad backing plate. Insert these or old backing plates with no friction material on them into the calipers & stomp on the brakes to move ALL the pistons forward in their bores. Then push back gently until you can just slip the new pad in & you should should have cured the over return.
The alternative is to strip & dry all fluid out of the braking system. Reassemble the calipers with pads, shims, pins & all. Blow the pads against the discs with compressed air & then bleed the braking system.
Good luck - I hope your problem is just not replacing all the pads at the same time.
12-18-2023, 01:00 PM
#73
Super Member
No definitely don't do that.
Just change the pads as normal, I have read this and very sorry to say I put no faith what so ever in the mentioned process, if it works for you great.
This comes from years and years of experience across all all types of cars changing all types of combinations front, rear, pads shoes drums and discs etc.
The purpose of the square calliper piston seal is to 1- seal the piston fluid in/dirt out, 2 to distort slightly when brake is applied so when brake is released the piston is drawn back slightly in to the calliper thus removing the disc pad from contacting the disc provide an air gap.
With a new seal the calliper piston moves back the most, with a well used aged seal the piston does not move back very far which can be felt if trying to spin the wheel while the vehicle is jacked up there is brake drag from the pads gently touching the disc.
If the front pads/brakes are worn out replace those there is no need to replace the rears unless you they are worn out also.
I would recommend bleed the brakes at the same time, and yes the brake will be soft for a week or two until the pads and discs have 100% surface contact and no- roaring up the road and stomping on the brakes will not fix this.
Just change the pads as normal, I have read this and very sorry to say I put no faith what so ever in the mentioned process, if it works for you great.
This comes from years and years of experience across all all types of cars changing all types of combinations front, rear, pads shoes drums and discs etc.
The purpose of the square calliper piston seal is to 1- seal the piston fluid in/dirt out, 2 to distort slightly when brake is applied so when brake is released the piston is drawn back slightly in to the calliper thus removing the disc pad from contacting the disc provide an air gap.
With a new seal the calliper piston moves back the most, with a well used aged seal the piston does not move back very far which can be felt if trying to spin the wheel while the vehicle is jacked up there is brake drag from the pads gently touching the disc.
If the front pads/brakes are worn out replace those there is no need to replace the rears unless you they are worn out also.
I would recommend bleed the brakes at the same time, and yes the brake will be soft for a week or two until the pads and discs have 100% surface contact and no- roaring up the road and stomping on the brakes will not fix this.
It's odd to me that you dismiss something that is clearly documented and how so many people have found this thread and commented on the exact same issue... then following what was stated in this thread and after doing so, the problem is no longer there? Seems pretty closed minded or just being stubborn..
I have changed brakes/rotors/calipers for years. I've never once experienced this issue at all on any car. I changed my e350's brake calipers to the OEM e55 8 piston fronts and 4 piston rears. I even completely rebuilt the calipers. Had ALL new hardware and piston seals..etc. I know how to rebuild a caliper and it was not done incorrectly.
Pedal would go damn near to the floor before engaging anything. I know how to bleed the brakes. I have several methods and several pressure systems that aid in doing so. I'm not green when it comes to that at all.
I think I bled the brakes at least 4-5 times. Pedal would still engage at the very bottom of the stroke. It wasn't until I did exactly what was mentioned in this thread and having the piston extend further by doing each side of the caliper one at a time and then doing a final bleeding. Drove the car and the brakes worked exactly how it should, strong upper pedal engagement for braking.
I think I even took pictures of the space that I could physically see that the pistons weren't coming back to an extended position. Again, nothing was wrong with the calipers/hardware/rebuild or what I did to install it.
Also having brakes feel soft for a week or two is nonsense. If you bed the brakes in properly, they should be pretty much good to go in less than 20-30 minutes. No way would I want to drive a car that had soft brakes for a week or two... clearly that's not right and or just laziness of bedding the pads to the rotors.
-Nigel
