Brake Pedal is Soft after changing discs and pads

[Luis Botez]

Hello Guys,
I’ve been watching the forum for some time, but never posted.
About 1 month ago I’ve changed my front discs and pads with Brembo and since then I’ve noticed my pedal not being as stiff as before and not catching from the tip but rather further. Brakes work well, I did a few checks after on the motorway and it does stop. Few days after this I did bleed the brakes, but to no avail so I’ve decided to wait for when my service comes.
Today I’ve took the car to MB Watford and I had Service B which included changing of brake fluid, but no impact on the pedal.
What do you guys suggest I should do, or what you guys think I did wrong and it got me into this?
Thanks!

 

[bembo449]

try bleeding abit of fluid out each side , sometimes the little bit of fluid inside the calipers gets passed its best from being heated / cooled so much , makes it spongey to the pedal , drawing a bit of fluid just refreshes it and with any luck will restore the pedal feel

 

[onefortheroad]

Crack a nipple open and push the piston in 1st , this will empty the fluid behind the piston ,then do a few bleeds ... otherwise all the fluid in the pipes will come out instead. Do this on all 4 wheels in a diagonal direction.

 

[Doug1234]

Not gone from semi metallic to ceramic pads by any chance ? ... these do work very well and less dust but they can lack feel / initial bite even though they give same results as semi metallic.

 

[mioba]

Who done the brake pad and disk change.
Were the disks degreased before fitting.

 

[Uncle Benz]

When you pumped the brake pedal to seat the new pads did you stroke it all the way to the floor? I recommend repeatedly pumping with small bites. Stroking the pedal to the floor can damage an old master cylinder. Try clamping all the brake hoses and see if the pedal goes shorter. If it doesn’t you may have a master problem. Air in the system can be diagnosed by pumping the pedal. If it shortens up when pumped but goes long again after a few seconds rest it’s likely to be air.

 

[mattkh]

When you pumped the brake pedal to seat the new pads did you stroke it all the way to the floor? I recommend repeatedly pumping with small bites. Stroking the pedal to the floor can damage an old master cylinder. Try clamping all the brake hoses and see if the pedal goes shorter. If it doesn’t you may have a master problem. Air in the system can be diagnosed by pumping the pedal. If it shortens up when pumped but goes long again after a few seconds rest it’s likely to be air.

Is this to be done with the engine running OR engine off..?

 

[Uncle Benz]

Running ideally

 

[Luis Botez]

try bleeding abit of fluid out each side , sometimes the little bit of fluid inside the calipers gets passed its best from being heated / cooled so much , makes it spongey to the pedal , drawing a bit of fluid just refreshes it and with any luck will restore the pedal feel

Will try this week as I plan to get the wheels out anyway. Should I follow a certain technique of do it standard, start with the further one and make my way towards the master cylinder?Thanks!

 

[Luis Botez]

Crack a nipple open and push the piston in 1st , this will empty the fluid behind the piston ,then do a few bleeds ... otherwise all the fluid in the pipes will come out instead. Do this on all 4 wheels in a diagonal direction.

This is exactly what I did 2 days after I’ve changed the pads and discs. Thank you!

 

[Luis Botez]

Not gone from semi metallic to ceramic pads by any chance ? ... these do work very well and less dust but they can lack feel / initial bite even though they give same results as semi metallic.

I will be honest with you and say I got not idea, but I don’t think so as I’ve fitted the non amg version from brembo as the car doesn’t have the amg package and they weren’t that expensive.

 

[Luis Botez]

Who done the brake pad and disk change.
Were the disks degreased before fitting.

I did the change and before fitting I used break cleaner on the discs, do you recon I did it wrong?

 

[Luis Botez]

When you pumped the brake pedal to seat the new pads did you stroke it all the way to the floor? I recommend repeatedly pumping with small bites. Stroking the pedal to the floor can damage an old master cylinder. Try clamping all the brake hoses and see if the pedal goes shorter. If it doesn’t you may have a master problem. Air in the system can be diagnosed by pumping the pedal. If it shortens up when pumped but goes long again after a few seconds rest it’s likely to be air.

I did small bites, but will do it again this coming week as I will rebleed all the weels and come back with an update.

 

[Luis Botez]

What I find strange is that although I might have done something wrong, not bleed properly or leave air inside, why the pedal hasn’t returned to hard feeling after MB done it as I would assume when the changing the break fluid they run it all out and then use a vacuum thing to put it back with the right pressure etc.

 

[mattkh]

......... although I might have done something wrong,

Provide a list of what you did wrong.

 

[curious]

I had a similar problem on my Vito. I went through everything suggested so far to no avail. It turned out to be corrosion on the pad hangers that were impeding the pad movement.
Only ever so slightly but enough to cause the symptoms you mention. It was particularily bad after changing pads.
If it is corrossion, get brutal with cleaning all the loose stuff off. Wire brush, shot blast, chisel, I used all methods.

 

[Luis Botez]

Provide a list of what you did wrong.

I don’t know what I could’ve done wrong except that I didn’t bleed on the same day, but 2 days later. Steps where, wheel out, calliper open, removed and secured, breake fluid reservoir lid open, piston pushed back with a C clamp, disc removed, brushed on the drum, brushed calliper and piston, grease drum, disc degreased with break cleaner, disc installed, grease calliper and pads, calliper installed, pads on, everything thighed and close, push pedal a few times with engine off until it gets hard.
One thing I didn’t mention is that when engine is off, after 3-4 pushes the pedal gets hard as a rock, but once I start the engine I feel it going a little down and soft.

 

[Doug1234]

Pedal going down after engine started is normal , its the servo doing its job helping pull the pedal down reducing effort needed.

 

[mattkh]

About 1 month ago I’ve changed my front discs and pads with Brembo
Thanks!

What brand calipers has the car got..?

 

[mattkh]

I don’t know what I could’ve done wrong except that I didn’t bleed on the same day,

Thanks very much for the deatiled reply.
If there was only 1 piston to push back with the c clamp, then the caliper must be a sliding caliper.
These slide on a pin when the brakes are applied.
These pins should be removed, cleaned and greased when you change the pads.