akgarage

Need some info regarding bleeding the brakes on a 2012 C63.Did a search but didn't find anything out of the normal.

Basically the brake calipers got powdercoated.When removing the calipers the lines were plugged so the fluid would stay in the lines.This is to minimize the amount of bleeding needed vs letting it all drain out and starting from nothing.

Pistons were removed from caliper,all threaded holes plugged,etc.I've done this 40+ times on many makes of cars and bikes.

After installing the brakes again the fronts are spot on.They grip just how they're supposed to.The problem is with the car off the pedal is fine.But once you turn the car on the pedal gets spongey.The rear brakes are the ones giving problems.They don't engage until the pedal is primed like 2 times then they finally grab.

We have bled the brakes for hours using both pedal pumping and mighty vac.Tried it with both the car on and off.Also removed rear calipers to check piston install and they move freely.The issue seems not enough pressure builds for it to reach the rears right away.We have tried everything pretty much.

There is a strong air sound coming from the engine bay which leads me to believe it could be the master cylinder.I just don't see how removing the calipers could make it go out.The brake booster is fine.

I have worked on countless M3's,Lexus even Lamborghini never gave me this problem.

Is there something special needed for this car to properly bleed the system?

abcut973

Nope. The normal bleeding process applies to this car. When I swapped my calipers I do not remember having this issue. Really strange what is happening to you. I know the front brakes are doing 80% of the job but I don't think the rear calipers engage after several pedal pressures .
That sound you have in the engine bay is when you press the pedal?

shades

Sounds like there may be some debris in the piston in the rear. I assume you tried the old method of gravity bleed. Try to push the brakes while it's bleeding don't lock the piston though, peel back the boot and spray some lube in there. Just giving suggestions at this point bro, because your doing all the right things

shades

Also, try bleeding the booster as well. maybe air in there or one of the vacuum line is pinching somewhere...inspect the whole system. because what your describing is usually air in the system still, but seeing that you did this countless times, you sound like you know what your doing.

-Marlin-

Don't care how many cars you've worked on.

You jacked the cylinder and lost pressure to the rear because of it.

I live in reality not what should have happened based on "expertise". Good luck cause it aint cheap.....

Ingenieur

On some cars you have to hook a diagnostic tool up and cycle the abs valve bank to get the air out while using a pressure bleeder

Did the reservoir ever go dry?

Ingenieur

I would try a pressure bleeder
From what I can determine they take 2 atm (30 psi) to do properly
And no way can you get that with vaccum

shades

If you didn't bleed the booster, try that. I assume you didn't let it go dry, because that's a big no no. I don't how long you left the calipers off for but if it was long enough to empty your gonna have to bleed the master. Also like Ing suggested, try to hook up a scanner...sometimes they are electronic and are done by a scanner. I personally never bleed my master on my car so don't really know if you need a scanner or not.

Jasonoff

With a pressure bleeder you're supposed to slowly pump the brake pedal while bleeding if you've had the system open.

I can send you the WIS instructions if you PM me your email.

Ingenieur

Thank you

If system was opened nice slow, consistent pedal pumping and release
Slow and methodical pump AND release
Pressure on system 30 psi
Normal bleeding sequence
Valve open while pumping until clear/no bubbles then close

I LIGHTLY TAP the calipers with a rubber mallet while bleeding to dislodge any trapped air

motoman

I posted to another thread about using a vacuum can . Used for years all on models. Second 2 year bleed did go bad on C63 with low pedal so I bled them again. Apparently I had let the reservoir go dry. I usually pull out most of the reservoir fluid to speed up the fresh. Did not touch key. I bleed and then drive and actuate the ABS to circulate the old fluid, then bleed again.

jvanbrecht

I like the pressure bleeders versus the vacuum type, less chance of accidentally draining the system dry.

I use autoenginuity to actuate the brakes while doing the pressure bleeder does it's thing (can also be done with STAR obviously).

hrloo

Sorry to revive an old thread. Was just reading through here to find some more specific guidance on how to flush the brake fluid.

Would it be possible to send me the WIS instructions as well?

Cheers!