Brake pedal feels crap ‍♂️

[Sam204]

Hi all. I’m really hoping someone could advise me. I have a 2012 C220 cdi w204 and last week it passed an MOT without an advisory. Drove home to find I had no brakes.

Long story short they had corroded excessively under the passenger side and were leaking. I had to leave the car a few days until the weekend when I could replace the brake lines. I replaced the rear brake lines for copper all the way from the ABR unit back, I also replaced the nearside front brake pipe while I was at it and the offside front was fine so I just rust cured and painted it. I’m a mechanic and made a bloody good job of the brake pipes.

Heres the problem, I have pressure bled the brakes to death, even while pulsing the ABR module and opening ABR valves via my diagnostics. I just can’t get a decent pedal. Long travel until it eventually bites and sort of works.

I had no issues at all until I replaced the brake pipes. My best guess is there is air trapped in the master cylinder or still in the ABR that won’t bleed out.

I read a thread on here with a guy who had a w212 and had the callipers removed for painting and had the same symptoms as me and he remedied it by bleeding the brakes with the rear callipers removed and moved about to free trapped air. Tried this to no avail.

I worked as a Merc tech for 8 years, love my mercs and have been a tech for 15 years. If anyone has experienced this or could help I would very much appreciate the input. Thanks

 

[Jockcl500]

I assume that you have double checked all the pipe connections for leaks, when pressure bleeding the engine is off, and no air bubbles are coming out of the bleed nipples.

 

[DSM10000]

Hi all. I’m really hoping someone could advise me. I have a 2012 C220 cdi w204 and last week it passed an MOT without an advisory. Drove home to find I had no brakes.

I worked as a Merc tech for 8 years, love my mercs and have been a tech for 15 years. If anyone has experienced this or could help I would very much appreciate the input. Thanks

Whilst not wishing to appear rude how can an MOT Tester not notice brake pipes in such poor condition that they failed on the way home and not even issue an advisory plus, had you not checked the car and noticed yourself as a "Merc tech for 8 years" etc

At the very least I would be reporting the MOT station for appalling lack of care.

 

[Sam204]

Whilst not wishing to appear rude how can an MOT Tester not notice brake pipes in such poor condition that they failed on the way home and not even issue an advisory plus, had you not checked the car and noticed yourself as a "Merc tech for 8 years" etc

At the very least I would be reporting the MOT station for appalling lack of care.

I had just bought the car a few days before, don’t have a ramp to get underneath and with all the plastic covers underneath they didn’t see the rusty part. They obviously failed after some very firm braking on the rollers and I agree they should’ve noticed the dripping afterwards.

yep all connections are fine and leak free.

 

[pmcgsmurf]

Had this before with W204 in the workshop and heavy brake testing bursting bad lines, they are very bad for corroding.

Did you actually replace with copper or is this a typo ?

 

[Sam204]

Had this before with W204 in the workshop and heavy brake testing bursting bad lines, they are very bad for corroding.

Did you actually replace with copper or is this a typo ?

Hi, yeah I used 3/16 copper brake line. Rather than cutting and flaring the original lines I replaced directly from the ABR unit, the two pipes from there all the way to the rear callipers and from the abr to the nearside front calliper. Made a real neat job of it with great flares and can’t see any issues with my work. I have replaced brake pipes like this on many other cars and not had the issue. My thinking is as this sat for a few days with the leak maybe it allowed air to enter when normally in the past when I have changed them they weren’t already leaking.

 

[Sam204]

Had this before with W204 in the workshop and heavy brake testing bursting bad lines, they are very bad for corroding.

Did you actually replace with copper or is this a typo ?

Hi, yeah I used 3/16 copper brake line. Rather than cutting and flaring the original lines I replaced directly from the ABR unit, the two pipes from there all the way to the rear callipers and from the abr to the nearside front calliper. Made a real neat job of it with great flares and can’t see any issues with my work. I have replaced brake pipes like this on many other cars and not had the issue. My thinking is as this sat for a few days with the leak maybe it allowed air to enter when normally in the past when I have changed them they weren’t already leaking.

 

[pmcgsmurf]

Hi, yeah I used 3/16 copper brake line. Rather than cutting and flaring the original lines I replaced directly from the ABR unit, the two pipes from there all the way to the rear callipers and from the abr to the nearside front calliper. Made a real neat job of it with great flares and can’t see any issues with my work. I have replaced brake pipes like this on many other cars and not had the issue. My thinking is as this sat for a few days with the leak maybe it allowed air to enter when normally in the past when I have changed them they weren’t already leaking.

Copper is not suitable for brake lines imho, especially not on some cars where the pressure can be quite high.
It is soft and prone to fracturing more easy at the joints.

We always use Copper Nickel (Kunifer), much better material, a bit harder to work with but much better.

 

[Deleted member 149005]

Air in the ABS unit?

Don't you need star to bleed the unit?

 

[Sam204]

Air in the ABS unit?

Don't you need star to bleed the unit?

That may be my next option, i can pulse the abs while bleeding and open valves with my diagnostics but star may have a better way

 

[Bellow]

I had no issues at all until I replaced the brake pipes. My best guess is there is air trapped in the master cylinder or still in the ABR that won’t bleed out.

More accurately, you had no issues until the brakes failed.
When they did, did the pedal go to the floor? If so, possibly damaged a master cyl seal which is now drawing air on pedal release?

 

[190]

Two years back when my car was being MOt'd at Kwikfit , it failed on a corroded rear brake pipe. They replaced it with copper and as far as I know had no trouble bleeding to a firm pedal. Would Kwikfit have star ? I wouldn't have thought so.

I'd be interested to know exactly where your brake pipe failed. Was it up over the back axle like mine or under the body shield.

 

[Bellow]

If copper is so bad - why is still sold for making brake pipes?
I use it and have never had a problem with it - ever.

I've also had the corroded and burst steel pipe. In the sill behind the plastic undertray - perfect mud trap. It failed when I was really standing on the brakes trying to get a sticky wheel cylinder to move - it didn't.

 

[pmcgsmurf]

If copper is so bad - why is still sold for making brake pipes?
I use it and have never had a problem with it - ever.

In some countries it is actually illegal, perhaps the better question is why.

Al lot of folks just use copper as it is easier to bend and form than copper-nickel.

 

[190]

A more important question than copper vs copper nickel is why does MB use crappy steel lines that fail in under 8 years.

 

[ToeKnee]

Cost?

 

[rf065]

A more important question than copper vs copper nickel is why does MB use crappy steel lines that fail in under 8 years.

Probably as they can be easily manufactured and bent into shape then just offered up to the underside of the car in one piece before anything else that would get in the way is fitted.
It's when they need replaced that the owners have the headache.

 

[Teego]

Anyone tried braided flexy hoses?

 

[ernie]

Anyone tried braided flexy hoses?

The full length of the car?

ERnie

 

[MrGundam]

Sorry to dig this up but it seems my C207 has a corroded breakline under the undertray.

Does anyone know if you can buy pre formed lines for these in Copper Nickel (Kunifer)? Thanks