C220 w204 brake pedal spongy

[Amg 007]

Hi guys

Need some help On my c220 auto w204 2009 brake pedal is spongy, pedal goes all the way down before brakes work. Garage have changed the master cylinder for another used one bled system no obvious leaks but still no difference, could it be a faulty servo/booster unit or do I try another bmc ? Thanks

 

[markjay]

The servo vacuum booster provides braking assistance, if it failed, the pedal would be harder, not softer. In any event, the garage would have checked it when replacing the master cylinder (which is connected to the servo).

Assuming there are no leaks and youre not actually losing any brake fluid, you may have an issue with one or more of the flexible hoses (leading to the calipers), if the flexible hose is damaged it will expand when the pressure goes up abd you'll get a 'soft' brake pedal.

Another issue could be a fault ABS box, but this is less likely.

 

[Amg 007]

The servo vacuum booster provides braking assistance, if it failed, the pedal would be harder, not softer. In any event, the garage would have checked it when replacing the master cylinder (which is connected to the servo).

Assuming there are no leaks and youre not actually losing any brake fluid, you may have an issue with one or more of the flexible hoses (leading to the calipers), if the flexible hose is damaged it will expand when the pressure goes up abd you'll get a 'soft' brake pedal.

Another issue could be a fault ABS box, but this is less likely.

Do you mean the ABS pump module
As I’ve tried another bmc with no difference
All lines are fine etc.

 

[Bellow]

Hi guys

Need some help On my c220 auto w204 2009 brake pedal is spongy, pedal goes all the way down before brakes work.

When and how did this begin? All of a sudden or gradually? After brake work? Anything else done prior to its appearance?

 

[Amg 007]

When and how did this begin? All of a sudden or gradually? After brake work? Anything else done prior to its appearance?

I purchased car with fault, as mentioned garage have tried two bmc, bled system & checked all pipework, still no difference
Garage have suggest to try ABS Module next.

 

[Amg 007]

Anyone know if the part no have to be exactly the Same as my current ABS module ? Have seen few online from same model c220 w204 2009 auto but all have different part no, thanks in advance.

 

[Bellow]

I purchased car with fault, as mentioned garage have tried two bmc, bled system & checked all pipework, still no difference
Garage have suggest to try ABS Module next.

Re ABS - I'm assuming it was bled in the procedure using STAR (or equivalent) to chatter the ABS valves - yes?

 

[markjay]

I purchased car with fault...

When did you purchase it? If you bought it from a trader, and less than 30 days ago, then you can still reject it.

If you bought it from a trader more than 30 days ago but less than a year ago, then rejecting the car is more complicated, but at least you don't have to foot the bill for the repair (under the Consumer Rights Act 2015).