Introduced Air While Flushing Brakes

[boba7523]

Hi guys,

I was doing my year 2 maintenance and flushed my entire brake system using the Motive pressure power bleeder but have introduced air to the last caliper because I ran out of brake fluid in the bank.

While I was releasing old fluid, I started seeing air bubbles come out and suction sound indicating there's no more fluid left in the bleeder tank.

I immediately tightened the bleeder screw and checked the brake cylinder and saw that it was empty (below minimum). Prior to starting, I made sure to fill it to "Max."

My question is, what should I do to correct this?

• Do I just fill the brake cylinder back to full and fill the bleeder tank, and finish off the flush, or would I have to start everything over again?
• Or did I cause an even more serious problem?
• I've heard to never let the brake cylinder run empty to avoid introducing air but I'm afraid that's what happened thus causing the air to come out while bleeding.
• FWIW, I never pressed the brake pedal the whole time I was doing the flush, not sure if it matters...
• Also, I'm concerned about air in the ABS system now and I'm not sure how to resolve that with ISTA+

Thanks for your help

[spammysammich]

Fill the brake reservoir up to the max line, then fill the motive tank up. Always over-fill to avoid these kinds of situations. I realize brake fluid can be expensive but why risk under-filling the tank like this and introducing air? You should be able to evacuate all the air but definitely do the ISTA workflow to trigger the pump and bleed the ABS properly just in case. I have not run it myself as I am still new to BMW tools, I'm sure somebody else can advise on the how-to.

[spammysammich]

thankfully it is the last caliper so it should be the shortest distance/amount of fluid to flush.

[boba7523]

Originally Posted by spammysammich

Fill the brake reservoir up to the max line, then fill the motive tank up. Always over-fill to avoid these kinds of situations. I realize brake fluid can be expensive but why risk under-filling the tank like this and introducing air? You should be able to evacuate all the air but definitely do the ISTA workflow to trigger the pump and bleed the ABS properly just in case. I have not run it myself as I am still new to BMW tools, I'm sure somebody else can advise on the how-to.

Just get air out of the last line and I don't have to re-do all of them?

If brake pedal mushiness indicates air in the lines, what kind of symptoms should I expect air in ABS to have?

[spammysammich]

if you didn't push air to any of the other lines they should have no air in them.

[spammysammich]

https://www.m3post.com/forums/showth...abs+activation

found this in the brake flush DIY, make sure you research the DIY section. hope it helps

[boba7523]

Originally Posted by spammysammich

https://www.m3post.com/forums/showth...abs+activation

found this in the brake flush DIY, make sure you research the DIY section. hope it helps

Thank you. If I have a 6 speed, would I have introduced air to the clutch cylinder? I have an F87 M2, so I'm not sure if it's the same as E92 platform.

[spammysammich]

You would be better off asking I that forum to be honest. There is a very active community over there and plenty of DIY guides.

[spammysammich]

Also, doubtful on the clutch. You have to give air an avenue to travel if you didn’t crack the clutch bleeder why would it move down that circuit?

[M3SQRD]

Originally Posted by boba7523

Thank you. If I have a 6 speed, would I have introduced air to the clutch cylinder? I have an F87 M2, so I'm not sure if it's the same as E92 platform.

Doubtful. However, here’s a link to a good video on cycling the f8x/f87 DSC/ABS lines.

https://f80.bimmerpost.com/forums/sh...58&postcount=1