Pagz

Guys,

I have bleed my brakes a lot with pressure bleeder @ 2 Bar(WIS spec)

When the car is off with bonnet up and I press the brake down I can clearly hear bubbles in the ABS/ESP unit move back and forth.

If any of you have time can you please try this and let me know if you have the same sound

WIS just says to bleed 80cc RR,RL,FR,FL and your done even when changing the entire ABS unit. I used SDS to cycle the pump and valves many times but it made no difference to the air bubble sound, I cannot find anything online about it...There are many complaints about the initial response of the C43 brake pedal

Ausmbtech

If you've replaced the ABS pump I would bleed more than 80cc out of each caliper, more like 200-250cc. Use a clear hose on the bleed nipple and only stop when there are no air bubbles. Make sure the car is level when you're bleeding it. For problem cars you can use both the pressure bleeder AND have someone pressing the brake pedal like a manual bleed too, this is good for troublesome air bubbles.

Remember though, the soft pedal in a C43 wont be fixed by bleeding, it's a design issue (master cylinder too small and overly assisted brake booster).

Pagz

Thanks, yes tried pressure bleed + somebody on the pedal, later even tried all of it while cycling the pump in all available options in SDS.

I have only replaced the callipers.

The main concern is that I can hear air bubbles in the ABS unit when engine is off and the brake is pressed firmly, does anybody else have the same sound?

Super B

Hey bud can you post up a video so we can hear it?

Ausmbtech

It's normal to hear fluid flow through the abs pump when pumping the pedal or bleeding the brakes with the engine off. It can sound like air in lines.

Pagz

Thanks,I hope it is normal!, it sounds like it comes from the "V" line going into the unit, it has the pressure sensor on it.

I will try take a video tonight so we can be sure!

Pagz

Ok here we go -

Ausmbtech

Sounds ok to me. As long as there aren't any air bubbles coming out of the bleed hose I say you're good to go.

Pagz

Thanks, I cant get my head around how this sounds compared to all other ABS units I have checked, all others you can hear the fluid move but is sounds like fluid moving and it is very subtle/barely noticeable...this is much louder and sounds like bubbles passing through a restriction...could check valves(ball bearings if they are) cause the sound I have?

DRBC43AMG

I have never noticed any sound coming from the ABS unit. OK I've never really listened.
When I overhauled my brake (see link in my signature) a couple of years ago, I had removed all the callipers front and rear. All the fluid had run out and I also had to change a brake pipe (stripped thread) to the front right meaning that one of the pipes to the ABS unit was removed and open to air. When I renewed the fluid (Super Blue) and bled the brakes, I used 1 can and a half to do the job using a brake bleeder too (excellent piece of kit). Bleeding you need to proceed from the furthest corner to the closest.
1. Rear right (furthest to the master cylinder)
2. Rear left
3. Front right
4. Front left (closest to the master cylinder)

My brakes work perfectly but I'll check for sounds from the ABS unit when I next open the hood.

Edited to add that the above bleed method is for a LHD vehicle. RHD will be reversed.

Pagz

Thanks man, if you could let me know if your sounds like this that would be great!.

Only thing I can think of is maybe my pressure gauge is very inaccurate or there is not enough air flow/to much pressure drop to push through the bubbles. it doesn't really flood into the catch container all that fast...

MaKega

Hi Everyone,
My car is a 98 C43 AMG and I had to replace the brake booster. After bleeding the brake system already twice (1,5 bar pressure at the reservoir, pumping the pedal by a helper, ignition on to power the ESP valves) the sound in the ABS/ESP block is still very similar to the one in the video above, like air in the lines. The pedal is not soft, driving feels OK.

Could you solve the issue/feature instead? Did you use a Star Diagnosis while bleeding?
Thanks,
Martin