Mercedes c180 1.8 cgi bluemotion brakes fade away

[Steviemojo]

Hi all my estate is having a bad braking problem the brakes seem to work fine when driving but sat still if I push the pedal it’s starts fading away I have had a new master cylinder fitted and fully flushed with fluid and new fluid replaced and still doing the same the abs unit doesn’t show any faults at all so I’m just wondering if there is anything I have missed or any idea what the problem could be

 

[grober]

Maybe you have a vacuum diaphragm leak on the brake booster or its supply?

 

[Steviemojo]

Maybe you have a vacuum diaphragm leak on the brake booster or its supply?

Cheers mate I’ll check that

 

[Steviemojo]

Maybe you have a vacuum diaphragm leak on the brake booster or its supply?

Do you have any diagrams of the vacuum pipes thanks

 

[grober]

BRAKE BOOSTER MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)

BRAKE BOOSTER MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)

mercedes.7zap.com

from

BRAKES MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)

BRAKES MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)

mercedes.7zap.com

 

[Bellow]

sat still if I push the pedal it’s starts fading away

Do you mean falling away?

I have had a new master cylinder fitted

Was the MC bench bled before fitting?

 

[Steviemojo]

BRAKE BOOSTER MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)

BRAKE BOOSTER MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)

mercedes.7zap.com

from

BRAKES MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)

BRAKES MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)

mercedes.7zap.com

Brilliant mate thankyou I’m gona have another look at it tommoro I’ll check full vacuum system I also had it on the brake tester at the garage and it’s only the rears that are fading any more clues if there’s a solution ?

 

[Steviemojo]

Do you mean falling away?

Was the MC bench bled before fitting?

Yes mate was bench bled

 

[Steviemojo]

Yes mate was bench bled

And I meant falling away sorry

 

[Bellow]

And I meant falling away sorry

Doubt that the servo is the problem them.
Did you cycle the ABS unit during bleeding?

 

[Steviemojo]

Yes mate that was done aswell . I bench bled cylinder fitted it then removed air from pipes to abs unit checked and bled all nipples - bled brakes all in correct order and full flush with no air in any fluid lines and it still the same . The thing is when I’m driving the car they work perfect but when I stop push the brake spedal stays up for a second then starts falling away

 

[Bellow]

Yes mate that was done aswell . I bench bled cylinder fitted it then removed air from pipes to abs unit checked and bled all nipples - bled brakes all in correct order and full flush with no air in any fluid lines and it still the same . The thing is when I’m driving the car they work perfect but when I stop push the brake spedal stays up for a second then starts falling away

I have a milder version of what you have (non MB) which I attribute to not cycling the ABS during bleeding (haven't sourced the appropriate scan tool yet). In a recent thread here, someone suggested that this pedal behaviour is perfectly normal. All three of us appear to have no problems with the actual braking performance.

 

[Steviemojo]

I have a milder version of what you have (non MB) which I attribute to not cycling the ABS during bleeding (haven't sourced the appropriate scan tool yet). In a recent thread here, someone suggested that this pedal behaviour is perfectly normal. All three of us appear to have no problems with the actual braking performance.

I have seen this before also mate but my car failed it’s mot because of this so I don’t know what to do as when I’m driving they w

 

[Steviemojo]

I have seen this before also mate but my car failed it’s mot because of this so I don’t know what to do as when I’m driving they w

They work perfect but it won’t pass mot

 

[Bellow]

I have seen this before also mate but my car failed it’s mot because of this so I don’t know what to do as when I’m driving they w

Find the MOT Tester Manual (on-line) and read the section on brakes. Providing the braking performance is adequate, I'm not sure a fail can be issued for what is pedal feel - unless the pedal bottoms out that is.

 

[DSM10000]

They work perfect but it won’t pass mot

What was the exact MOT failure?

 

[Steviemojo]

Find the MOT Tester Manual (on-line) and read the section on brakes. Providing the braking performance is adequate, I'm not sure a fail can be issued for what is pedal feel - unless the pedal bottoms out that is.

Yeah the pedal is bottoming out when sitting still it goes up to the green which is fine and then slowly just fades away to nothing mot tester said

 

[Steviemojo]

What was the exact MOT failure?

 

[Steviemojo]

Replaced master cylinder and just exactly the same mate and as I’ve said when I’m driving it works spot on

 

[Bellow]

Yeah the pedal is bottoming out when sitting still it goes up to the green which is fine and then slowly just fades away to nothing mot tester said

Clearly issues with rear brakes there. Are they sorted and the pedal problem persists?