Bleeding...a ton of air and still not done

[ChrisFuture8]

Wanted to know how crazy the situation is with the air in my brakes system.
I have had issues with dragging brakes as well as weak break pressure.

I have rebuilt all four calipers, replaced the master cylinder, new pads and rotors all around and flushed the system.

I still get an occasional ABS brake assist failure light up and ASC indicator on.

Yesterday, I had the car on a lift at a DIY garage, and the rear right wheel bleed to 1 liter of brake fluid and yet, there were still a lot of air coming out.
I wasn't sure why 1 liter had drained out and still air bubbles coming out strong on that tire. So I capped that off and went on to the left rear wheel. Again, just
like the other wheel. I could have let it bled for a liter and still get air bubbles.

The front right and front left were good...hardly any bubbles out from those two wheels.

The brakes stop better but still takes 2 pumps at the pedal. So the question is, how much more do I need to bleed the rear calipers?
Is that normal or there's a bigger issue I'm having?

So far, the brakes are no longer dragging which is 1 issue resolved/fixed.

All inputs are appreciated.

[BMSman]

Are you sure the air bubbles are not air being drawn in at the bleed nipple? I vaguely remember having a similar issue (endless bleeding with air bubbles) and believe i added some teflon tape on the bleed nipple threads to solve it.

Did you orient the pistons correctly (to allow any trapped air to escape)? Try tapping the calipers with a mallet to get any air bubbles to rise towards the bleed nipple.

Wanted to know how crazy the situation is with the air in my brakes system.
I have had issues with dragging brakes as well as weak break pressure.

I have rebuilt all four calipers, replaced the master cylinder, new pads and rotors all around and flushed the system.

I still get an occasional ABS brake assist failure light up and ASC indicator on.

Yesterday, I had the car on a lift at a DIY garage, and the rear right wheel bleed to 1 liter of brake fluid and yet, there were still a lot of air coming out.
I wasn't sure why 1 liter had drained out and still air bubbles coming out strong on that tire. So I capped that off and went on to the left rear wheel. Again, just
like the other wheel. I could have let it bled for a liter and still get air bubbles.

The front right and front left were good...hardly any bubbles out from those two wheels.

The brakes stop better but still takes 2 pumps at the pedal. So the question is, how much more do I need to bleed the rear calipers?
Is that normal or there's a bigger issue I'm having?

So far, the brakes are no longer dragging which is 1 issue resolved/fixed.

All inputs are appreciated.

[ChrisFuture8]

BMSman, I think you may be spot on with air getting pulled in at the bleed valve (nipple). I may have caused that be over loosening the valve more than necessary. I did some googling and others have wrote about the same situation. I also use the Motive pressure bleeder.

[brettd85]

If using a pressure bleeder I don’t think that will introduce air through the bleeder threads. I would expect that with a vacuum. Dumb question but the motive tank has fluid in it? Pedal should be firm obviously. I haven’t had any issues with my motive bleeder but maybe you have a faulty one that’s pushing air in. Could try with someone on the pedal.

[ChrisFuture8]

Nowadays, it's hard to get someone to sit there for a couple hours to go through an entire brake system bleed/flush. Yes, I pour in a full liter of fresh fluid each time and keep an eye on the level to ensure there's always fluid in the tank. I see air bubble in the clear line from the motive tank to the master cylinder reservoir but from what I read, that seems to be normal.

[cartoonz]

Nowadays, it's hard to get someone to sit there for a couple hours to go through an entire brake system bleed/flush. Yes, I pour in a full liter of fresh fluid each time and keep an eye on the level to ensure there's always fluid in the tank. I see air bubble in the clear line from the motive tank to the master cylinder reservoir but from what I read, that seems to be normal.

Use a Pressure Bleeder and none of these things will matter.

[ChrisFuture8]

This is what I use, Harold.

https://www.amazon.com/Motive-Produc...07457373&psc=1

[rjjablo]

Both of my kids know how to bleed brakes

Nowadays, it's hard to get someone to sit there for a couple hours to go through an entire brake system bleed/flush. Yes, I pour in a full liter of fresh fluid each time and keep an eye on the level to ensure there's always fluid in the tank. I see air bubble in the clear line from the motive tank to the master cylinder reservoir but from what I read, that seems to be normal.

[ChrisFuture8]

...funny. I don't have kids.

[Helmer]

Use a transparent hose from the nipple to the container? then just open the nipple and start pumping until you see no bubbles in the hose.

[ChrisFuture8]

Use a transparent hose from the nipple to the container? then just open the nipple and start pumping until you see no bubbles in the hose.

Yes, I have a transparent hose going from the bleed valve to the catch container. At the pressure bleeder, I maintain the pressure at 10-11 psi to ensure there's enough pressure in the system to push the brake fluid and air out of the system at each wheel. When the pressure in the pressure bleeder drops to 8'ish psi or so, I close the bleed valve, go and give a few pumps at the pressure bleeder to get it up to 10-11 psi again and continue with the brake fluid purge. Helmer, are you suggesting I should crack the bleeder valve open and pump the pressure bleeder for as long as it takes to purge all the air out at each wheel?

[Helmer]

I only use a transparent hose going from the bleed valve to the catch container. Then I pump with the brake pedal until no bubbles enter the hose.

[brettd85]

Sounds like you are doing everything right?? Weird.

[Money Pit]

Hi,

I found a substantial improvement in brake pedal feel when I replaced the brake line hoses with a stainless steel wound set from FPC Euro - all 6 pieces. A weakness in any of the rubber sections might affect the pedal feel of weak pressure. I guess any point in the lines which let air in are also likely to let fluid out. Maybe check the brake bomb. Also, it may seem a stupid question, but have you used the correct fluid? These things are very particular about the correct fluids.

[raidaru]

Hi, did u manage to bleed the whole air in the end? I have same problem with my 650Lci e64 and it's driving me crazy.

[ChrisFuture8]

To be honest, I can't remember what I did but I think I allowed it to bleed as much as I had fresh brake fluid to replenish the vacuum bleeder reservoir and close up the bleed valve at the caliper.

[m6bigdog]

FWIW,
The BMW pressure setting to pressure bleed the brake system is 2.5-3 Bar, 36-43 PSI.
Yes, it is unnerving to watch the reservoir expand and I rarely use that much pressure when bleeding my cars; typically less then 30 PSI.
Less pressure can be insufficient to flow enough brake fluid to overcome the bubble rise in the vertical brake lines.
Absent sufficient bleed pressure, I have found if the system has been allowed to drain from the caliper fitting (replacing a caliper, etc.) it is best to pedal bleed to get the system to a point where the lower pressure bleed will work. i.e., Fluid change or Bleeding air from the calipers only
Note:
Pedal bleeding has a couple issues:
1) It allows the master cylinder pistons to move the full cylinder stroke and that is into an area of the cylinder bore not normally traveled by the piston, so you should only do this with a system that is correctly maintained. i.e., regular fluid changes.
2) Pedal bleeding a system with a lot of air in the lines can cause micro bubbles to form in the brake fluid as it enters the caliper and you must allow sufficient time for these micro bubbles to settle out in the caliper so the system can then be completely/correctly bled.

[kallekula]

I got the motive bleeder too. Great tool and you won’t have to bother your spouse stomping on the pedal. ��