ABS Bleed - The Unofficial BMW M5 Messageboard (m5board.com)

M5 powered · 25th May 2009, 16:53

Hi Guys,

Does anyone know how to bleed the abs unit on the M5.

Have just changed the master cylinder and know I've introduced air into the system.

Have bleed the brakes all the way round, but alas, still have the pedal going to the floor.

Assume there is a bleed on the ABS unit itself, or I need to enable it with 12 volts somewhere?

Best

Jonathan

corneredge · 26th May 2009, 17:06

I suspect you have air in the brakes and should do a traditional bleed again. The ABS system allows fluid to pass through it "normally" or passively when not activated, so you don't need to activate the ABS to achieve a hard pedal. IF there is air in the ABS, activating the abs via slamming the brakes will cycle the air out. I agree, not the nicest way to do it, but only way I know of.

- Russ

M5 powered · 27th May 2009, 00:21

Thanks Russ,

Have been reading round the web and came to the same conclusion. I have re: bled the car but the brake pedal still goes to the floor with the engine running, even with what seems to be no air in the system. All the hydraulic lines are tight so am really scratching my head. Wouldn't mind if I hadn't of done this process numerous times before!

I did find two earlier posts where this had happened and it was a trip to the dealer. Really is bloody odd though.

kiudog · 27th May 2009, 01:52

i did change my master cylinder and did the bleeding on the connector on it....i don´t know if i sound silly, did you top the reservoir Almost to the top of it) and start the bleeding service? all the tubing and hoses are tight?

///Manuel · 27th May 2009, 05:51

Sometimes bubbles can be trapped in the master cylinder. You may try to tilt the car with a jack to lift the front (resp. back) of the car as you bleed in attempt to loosen air bubbles. Air may also get trapped in the calipers themselves. It takes a while but eventually it will all be bled away.

You can also try to suck fluid/air out by connecting a vacuum pump at the calipers themselves.

M5 powered · 29th May 2009, 00:32

thanks for the responses and suggestions.

Yes, everything is tight and the bleed works correctly. No air seems to be in the system having put 2 litres (collectively) through each corner. But the pedal still goes to the floor so something is very wrong.

Anyway, Autokraft are replacing the brake hoses with some upgraded stuff for me (the rears looks a pain to do with out a car lift) so they are picking the car up on Monday.

I will however report back.

Best

Jonathan

Konfused Pete · 29th May 2009, 02:19

The only thing I can think of on top of of what has already been suggested that is that maybe you needed to bench bleed the master cylinder before putting it in.

corneredge · 29th May 2009, 06:34

a gravity bleed by leaving a rear bleeder open over a long period of time may help as well.