[eblan]

I have a really weird issue after bleeding my brakes on my '11 328i xdrive. Google hasn't been a whole lot of help with this. So after bleeding my brakes my pedal got squishy. The pedal doesnt have much resistance until pressure builds up and only temporarily, but it doesnt go all the way to the floor, 2 inches above or so. They do seem to work ok but they aren't what they were.

The current symptoms I'm having is that there is air in the left rear line, the other 3 are clear. Ive bled several times but at this point I'm resigned to believe that there is a leak in the system, though I am not losing fluid and there are no visible holes or punctures in the lines exiting the dsc. I can hear hissing from the dsc while and soon after pumping my brakes, it's as if its breathing; I can hear air come out and go back in. Putting my ear right up to it, it does not sound like it's coming from the MC or booster, it is at or around the dsc.

I've run the bleeding procedure with ista multiple times, I can hear the hissing while doing so and air keeps coming out of the left rear caliper. The only code I'm getting is "low brake fluid" from the dsc. The motor sounds fine. There were no issues prior to bleeding the brakes. It's pretty clear to me that this is some type of leak in the system but it's only leaking air. I would assume it's the booster if I wasnt only getting air from the one wheel. Anybody have any thoughts on this? I appreciate any ideas anyone might have. Thanks!

[ahlbe1cl]

First step is to validate that you are bleeding the brakes properly. Since 3 of the 4 are fine, we can assume you are doing this correctly. Just to be sure though, this takes 2 people unless you have a brake pressure gizmo.

1. Friend applies pressure to the brake pedal.
2. You open the bleeder valve on the caliper
3. Let air leak out, let fluid leak out, tighten the bleeder valve

Remember that air compresses, fluids do not. Spongy means air in the line, doesn’t sound like a booster problem, but a bleeder valve problem...maybe it’s not tightening down enough...maybe you need a new caliper.

Don’t over think it. It’s not a BMW problem, it’s a brake system problem. What is happening to your car could happen to any make/model. Brakes aren’t really that unique between any car.

[eblan]

Definitely not thinking it's bmw specific, im a big fan. I bled the brakes with a motive pressure bleeder, had a friend help me with it, all he did was hang near the caliper and watch for air.

Bleeder valve could be an issue, have bled a few times now though and its consistently been the same wheel. Though it makes sense that if there was air in the system it could linger near the dsc as that's a high point in the system, odd that I'm not losing fluid though. Itll be worth going through and making sure everything is tightened down correctly though. Appreciate the reply.

[nsjames]

I did mine with a motive unit and had no issues, but it sounds as though maybe you have air in the DSC unit.

Have you any diagnostics software? ISTA has an DSC bleed procedure that actuates the pump motor.

IIRC it's in ista if you go into the DSC module you can call up the functions and then trigger the pump motor on.

otherwise I'd say go take it out and get on the brakes hard enough to cause the ABS unit to actuate, then attempt to bleed the brakes with the motive unit again. I've had success with that method on GM cars that I did not have the software to bleed the ABS unit properly.

[mweisdorfer]

Originally Posted by eblan

I have a really weird issue after bleeding my brakes on my '11 328i xdrive. Google hasn't been a whole lot of help with this. So after bleeding my brakes my pedal got squishy. The pedal doesnt have much resistance until pressure builds up and only temporarily, but it doesnt go all the way to the floor, 2 inches above or so. They do seem to work ok but they aren't what they were.

The current symptoms I'm having is that there is air in the left rear line, the other 3 are clear. Ive bled several times but at this point I'm resigned to believe that there is a leak in the system, though I am not losing fluid and there are no visible holes or punctures in the lines exiting the dsc. I can hear hissing from the dsc while and soon after pumping my brakes, it's as if its breathing; I can hear air come out and go back in. Putting my ear right up to it, it does not sound like it's coming from the MC or booster, it is at or around the dsc.

I've run the bleeding procedure with ista multiple times, I can hear the hissing while doing so and air keeps coming out of the left rear caliper. The only code I'm getting is "low brake fluid" from the dsc. The motor sounds fine. There were no issues prior to bleeding the brakes. It's pretty clear to me that this is some type of leak in the system but it's only leaking air. I would assume it's the booster if I wasnt only getting air from the one wheel. Anybody have any thoughts on this? I appreciate any ideas anyone might have. Thanks!

They way I have always done it is, I have my helper in the car. I say "open". After I say open, my helper immediately starts pumping 10x counting out loud. He says "hold", after pump no. 10. This means he is holding the pedal to the floor. When he says "hold", I shut the valve, and I say "shut", which tells him he can release his foot from the pedal. We do this 3x per caliper. Of course, I fill up the MC after each 10 pumps & put the cap back on the MC before we do another 10 pumps. We go, PR, DR, PF & DF, in that order.

I use a mitivac, air powered, brake suction tool to change out the brake fluid every 2 years. I also use the mitivac canister with the lines attached to it, as my container in which the excess brake fluid goes into, during the brake bleeding procedure, for it's air tight.

I know if you have a Foxwell or Schwaben scanner tool, there is an option in there that allows you to activate the ABS, in order to get any air bubbles out of that system. I have done that with this tool. Not that I really needed too, but it's extra piece of mind. I did this before I bleed the brakes.

[eblan]

Appreciate the input. I used a motive pressure bleeder with the ista/d bleeding routine and ATE dot4, I did RR, RL, FR, FL. The other 3 wheels are clear as a whistle, the rear left consistently has air. There's no fluid loss so its as if there's a leak somewhere that isn't being populated by fluid, which doesnt make sense. The connections are tight.