Mushy brake pedal feel after brake pad replacement.
12-17-2009, 05:54 AM
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W204 C280
Mushy brake pedal feel after brake pad replacement.
I had my brake pads changed at the dealership today and when I got the car back, my brakes felt really mushy and as if it wasn't biting. I tried to bed the brakes in a little but it still wouldn't really bite. They didn't change the fluid as I was told if your fluid is still good (which it was before I brought the car in for a brake pad replacement since the fluid was just replaced recently) then I don't need to have it replaced again. Any idea as to why the brake pedal feels a little mushy even after replacing the pads? Do I need to break in the brakes? Any help would be greatly appreciated.
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Chamelleon (08-26-2019)
12-17-2009, 08:27 AM
#2
I would go back to the dealer and ask them.
Initially I would suggest the brake lines weren't bled properly but it's just a guess without seeing the car in person, so again best to go back to the people who did the work.
Initially I would suggest the brake lines weren't bled properly but it's just a guess without seeing the car in person, so again best to go back to the people who did the work.
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skipper42 (12-18-2023)
12-17-2009, 08:54 AM
#3
Super Moderator
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.
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12-17-2009, 02:08 PM
#4
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Hello Glyn,
I would be grateful to know why only changing the front pads would result in a soft pedal ? . In my previous vehicles I have only changed the front discs & left the rears alone as they have been far from worn out. Other cars have drum rears & did not require changing either without any problems. I believe 80% of braking can be attributed to the front wheels. Thanks , Old Carsey!!
I would be grateful to know why only changing the front pads would result in a soft pedal ? . In my previous vehicles I have only changed the front discs & left the rears alone as they have been far from worn out. Other cars have drum rears & did not require changing either without any problems. I believe 80% of braking can be attributed to the front wheels. Thanks , Old Carsey!!
12-17-2009, 03:36 PM
#5
Super Moderator
Carsey - It's a variation of the over return theme on these cars. Partially worn rear pads & new fronts leaves you with greater fluid requirement to engage the rears than the front. This unbalances the 2 circuits requiring just one light pump of the pedal to regain the ideal pedal movement or firmness of pedal. It's hit and miss depending on stiction in the rear calipers. Sometimes you get away with it & sometimes you don't. You have no idea how many cars this plagues. Mine included.
Your braking bias front to rear is correct but has nothing to do with this situation.
BTW - the term stiction comes from the shock absorber industry & describes the stick/slip action of seals on the shaft. The sames applies to the action of the D shaped cross section seal on a caliper piston operating in the bore. The D section seal looks a bit like an O Ring. If it sticks to the bore instead of sliding down the bore you suffer over return. We are talking pretty small movements here.
You are lucky you don't own an Alfa - they are chronic for doing this. Our cars don't do it as badly but it's irritating nevertheless. I would have said it was a Brembo thing but older Alfa's with Lockheed Bonaldi brakes were even worse.
Your braking bias front to rear is correct but has nothing to do with this situation.
BTW - the term stiction comes from the shock absorber industry & describes the stick/slip action of seals on the shaft. The sames applies to the action of the D shaped cross section seal on a caliper piston operating in the bore. The D section seal looks a bit like an O Ring. If it sticks to the bore instead of sliding down the bore you suffer over return. We are talking pretty small movements here.
You are lucky you don't own an Alfa - they are chronic for doing this. Our cars don't do it as badly but it's irritating nevertheless. I would have said it was a Brembo thing but older Alfa's with Lockheed Bonaldi brakes were even worse.
Last edited by Glyn M Ruck; 12-17-2009 at 03:54 PM.
12-17-2009, 07:28 PM
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W204 C280
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.
I'll be sure to mention to the dealer your suggestions and see what they say. I'll keep you guys updated on progress. Thanks again!
12-17-2009, 08:31 PM
#7
Super Moderator
Uh Oh! Then the dealer probably pushed the pistons too far back when they changed the pads - make them fix it. Then if they damage something it is for their account. If the dealer has Benz trained staff they should know about it.
Good luck!
Good luck!
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12-17-2009, 11:32 PM
#8
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'08 C300 Lux Barolo Red Beige Leather P2 MM 18" wheels '84 944
Pad change
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.
The brake pedal should never be depressed when even one pad (of the eight) is out because of the danger of popping a piston out of a caliper. Who would, anyway?
Also, when my original dusty REAR brake pads were replaced under warranty, there was absolutely no difference in brake feel or braking performance.
Last edited by RLE; 12-17-2009 at 11:35 PM.
12-18-2009, 01:37 AM
#9
Super Moderator
The brake pedal should only be pressed if a safe spacer such as a pad backing plate is inserted. Pistons will not pop out if you run out of friction material by design. So a backing plate is a safe option.
The pads are not self adjusting - what you meant to say is that the pistons are supposed to be self adjusting. This is dependent on the D seal slipping in the bore. Sometimes it does not adequately. Piston return is entirely dependent on the seal returning to it's original shape.
You got lucky with your rear brakes & it is less inclined to happen if you only replace the rears because by fluid volume they require so much less displacement than the fronts.
Calipers over returning is a common problem in the industry. Go and talk to any OE brake component supplier, OEM or competent brake shop.
This problem does not only apply to Mercedes. Many other brands have this trouble. It's been around since Dunlop Disc Brakes on early racing Jaguars. The early 1950s.
Because it's outside your experience - does not mean that it is not so.
The pads are not self adjusting - what you meant to say is that the pistons are supposed to be self adjusting. This is dependent on the D seal slipping in the bore. Sometimes it does not adequately. Piston return is entirely dependent on the seal returning to it's original shape.
You got lucky with your rear brakes & it is less inclined to happen if you only replace the rears because by fluid volume they require so much less displacement than the fronts.
Calipers over returning is a common problem in the industry. Go and talk to any OE brake component supplier, OEM or competent brake shop.
This problem does not only apply to Mercedes. Many other brands have this trouble. It's been around since Dunlop Disc Brakes on early racing Jaguars. The early 1950s.
Because it's outside your experience - does not mean that it is not so.
12-18-2009, 04:31 AM
#10
MBWorld Fanatic!
In the W204 is the front/rear brake pad wear even ?
I have always repaired my own brakes for 45 years & never had a problem with soft pedals. Why did I buy a MB?
I have always repaired my own brakes for 45 years & never had a problem with soft pedals. Why did I buy a MB?
12-18-2009, 04:56 AM
#11
Super Moderator
If a little care is taken there is no reason for soft pedals.
12-18-2009, 09:07 AM
#12
Super Member
Well, fronts "used" to wear more quickly than the rears.... as seen by the excessive amount of brake dust on the front rims. However, the W204 develops this brake dust on the rear wheels, so I'm placing my bet on the rears needing replacement first on this car. Just my .02
12-18-2009, 10:27 AM
#13
Super Moderator
Our W204 350 Elegance still produces all the brake dust up front. Merc had a batch of bad rear pads out there that caused messy rear wheels.
12-18-2009, 11:07 AM
#14
Super Member
Oh, I recall talk about that -- but I think there was something about free replacement within 10-12k miles... I think I heard about this at 20k miles, so... yeah. I figure I'll just use them up and hopefully get "good" new ones? LOL.
12-18-2009, 11:17 PM
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'08 C300 Lux Barolo Red Beige Leather P2 MM 18" wheels '84 944
Wear which end?
The W203s have only three wear sensors and I replaced them all.
12-19-2009, 02:54 AM
#17
Super Moderator
Misinformation
As a W203 driver, you should know that the days of the fronts wearing out first is over. I drove the crap out of my C320 and at 44K miles, all eight pads were worn evenly and I replaced them. Just pushed all the pistons fully back and slipped the new pads in and after 1-2 pushes of the pedal they were adjusted properly and away we went.
The W203s have only three wear sensors and I replaced them all.
The W203s have only three wear sensors and I replaced them all.
BTW. The number of brake pad wear sensors on a 203 varies from one on some later cars LHS front to 4 as on my car. It depends on year & country of build. Some of the final cars delivered to the US only had 1 sensor. In the case of your 320 it obviously had three which means it should have been a pre facelift car or a so called 2004.5.
Cars fitted with Sport Pack in ROW or Sport designated cars in the US had different (larger) Brembo brakes up front & this changed wear ratios as well. Earlier cars like mine had sliding calipers up front - Later cars had fixed calipers and so on.
You really don't know these cars very well.
Last edited by Glyn M Ruck; 12-20-2009 at 11:40 AM. Reason: typo
12-19-2009, 03:14 AM
#18
Super Moderator
Mr Carswell. My car was still under the maintenance plan which has just expired when the front pads were changed with OEM stock pads. The guys were careless & I have a slightly longer travel pedal than before the change. One little approx 20% of pedal travel pump of the pedal regains the old pedal take point prior to pad change. They offered to redo the job but I declined because I want to fit ceramic pads all round which I've not got around to doing. The car still stops fine but it's irritating.
Last edited by Glyn M Ruck; 12-19-2009 at 04:02 AM.
12-28-2009, 06:35 AM
#19
Super Moderator
On the 203 forum LILBENZ230 has just gone 70,000miles on rear pads - they appear to have come to an end. He has had multiple sets of front pads & a set of front rotors. His car is a Sport with the larger Brembo calipers & rotors up front. His car is also one with zero rear brake wear sensors. He drives it hard.
So let's forget stories about even front & rear pad wear on these cars. It's highly service dependent.
So let's forget stories about even front & rear pad wear on these cars. It's highly service dependent.
12-28-2009, 02:39 PM
#20
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2012 C300 4Matic
As a W203 driver, you should know that the days of the fronts wearing out first is over. I drove the crap out of my C320 and at 44K miles, all eight pads were worn evenly and I replaced them. Just pushed all the pistons fully back and slipped the new pads in and after 1-2 pushes of the pedal they were adjusted properly and away we went.
The W203s have only three wear sensors and I replaced them all.
The W203s have only three wear sensors and I replaced them all.
05-18-2011, 09:51 AM
#21
Newbie
Regarding the 2008 post from Glyn Ruck, this is an EXTREMELY knowledgeable answer! It is well stated and, after 45 years and 2 factory licenses, 'wrenching', I am very impressed by how well this usually unknown, not particularly common, problem has been explained. Very, very impressive to me.
Last edited by TheGrandmaDee; 05-18-2011 at 09:53 AM. Reason: Neglected to specify the target post
12-22-2013, 08:15 PM
#22
hey everyone ..sorry Bit of a thread resurrection!..lol
i have seat leon cupra r with standard 4 pot brembos upfront and standard vag items on the rear
ive recently had all the calipers off my car to have them refurbished.. however on refitting them and bleeding them i've been left with a long pedal travel.. the brakes work ok .. and they pump up to very solid with the engine off but as soon as i start it there seems to be a fairly long pedal before they seem to do anything
now this is the first and only time ive ever heard anyone come up with this caliper over return problem that glyn mentions .. but it sounds exactly like what im getting and makes total sence!..its been driving mad.. i thought i must have air still in the system somewhere.
do you think think this could be my problem and has anyone tried his fix and does it work? or is it just worth waiting till it sorts itself out?..
thanks
matt
i have seat leon cupra r with standard 4 pot brembos upfront and standard vag items on the rear
ive recently had all the calipers off my car to have them refurbished.. however on refitting them and bleeding them i've been left with a long pedal travel.. the brakes work ok .. and they pump up to very solid with the engine off but as soon as i start it there seems to be a fairly long pedal before they seem to do anything
now this is the first and only time ive ever heard anyone come up with this caliper over return problem that glyn mentions .. but it sounds exactly like what im getting and makes total sence!..its been driving mad.. i thought i must have air still in the system somewhere.
do you think think this could be my problem and has anyone tried his fix and does it work? or is it just worth waiting till it sorts itself out?..
thanks
matt
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sdenney89 (02-18-2017)
12-23-2013, 07:47 AM
#23
Super Moderator
Caliper over return is a very real problem & frequently won't correct itself.
That said. When vacuum has been applied to the booster by starting the car you should feel a slight softening of the pedal but not excessive travel.
I'm not au fait with all the peculiarities of VW/Seat cars but they are using Brembo brakes & conventional ABS.
Presume you have done a pressure bleed from longest brake line first to shortest brake line last & observed/applied good practice? If this did not achieve a decent high pedal then fit a set of old very worn pads & stomp on the brakes with the engine running. Then remove the old pads & only push back the caliper pistons sufficiently to achieve insertion of the new pads. This will hopefully solve the issue.
My low mileage CLK was up for it's first set of front pads at service the other day. I supervised the Tech removing cleaning & inserting new pads. I now have the highest firmest pedal the car has ever had.
That said. When vacuum has been applied to the booster by starting the car you should feel a slight softening of the pedal but not excessive travel.
I'm not au fait with all the peculiarities of VW/Seat cars but they are using Brembo brakes & conventional ABS.
Presume you have done a pressure bleed from longest brake line first to shortest brake line last & observed/applied good practice? If this did not achieve a decent high pedal then fit a set of old very worn pads & stomp on the brakes with the engine running. Then remove the old pads & only push back the caliper pistons sufficiently to achieve insertion of the new pads. This will hopefully solve the issue.
My low mileage CLK was up for it's first set of front pads at service the other day. I supervised the Tech removing cleaning & inserting new pads. I now have the highest firmest pedal the car has ever had.
Last edited by Glyn M Ruck; 12-23-2013 at 08:23 AM.
12-26-2013, 06:51 PM
#24
hi glyn..merry christmas 
..thanks for replying...
yes i did full pressure bleed from the furthest caliper including 2 on the master cylinder it did get slightly better feel.. it isnt like major long the travel and the brakes did work as i could get the abs to kick in when i braked really hard.. it just didnt seem the same feeling towards the start of the pedal like it did before ..which make me think this could be the problem now
does this tend to effect brembos well i will certainly be giving this a try as it cetainly cant hurt anything
thanks
matt
..thanks for replying... yes i did full pressure bleed from the furthest caliper including 2 on the master cylinder it did get slightly better feel.. it isnt like major long the travel and the brakes did work as i could get the abs to kick in when i braked really hard.. it just didnt seem the same feeling towards the start of the pedal like it did before ..which make me think this could be the problem now
does this tend to effect brembos well i will certainly be giving this a try as it cetainly cant hurt anything
thanks
matt
12-27-2013, 06:13 AM
#25
Super Moderator
Hi ~ and Merry Xmas to you.
This problem can show itself on all cars with disc brakes going right back to Jaguar Mk2's with Dunlop disc brakes. I don't think Brembo are worse than others. I've seen this problem across a broad range of cars. People are more sensitive to it in the racing fraternity.
As I've said previously. Italian Lockheed Bonaldi twin booster brakes on older Alfas's were particularly sensitive to this. That was a particularly sensitive setup that did not like pressure bleeding either. They responded best to 2 man manual bleeding with pumping & holding the brake pedal while a second party cracked open the bleed nipples.
Good luck!
This problem can show itself on all cars with disc brakes going right back to Jaguar Mk2's with Dunlop disc brakes. I don't think Brembo are worse than others. I've seen this problem across a broad range of cars. People are more sensitive to it in the racing fraternity.
As I've said previously. Italian Lockheed Bonaldi twin booster brakes on older Alfas's were particularly sensitive to this. That was a particularly sensitive setup that did not like pressure bleeding either. They responded best to 2 man manual bleeding with pumping & holding the brake pedal while a second party cracked open the bleed nipples.
Good luck!
