How many times do you have to bleed, I am on my third time and still have only 50% braking, and locks up precisely at same point in commute, crazy, so will try to bleed again using pressure bleed. If you meant spring fluid, or is it spraying fluid out, or does it mean the same?

The only way I'm aware of to properly bleed x5 is with a pressure bleeder and a scan tool that will engage the prechatge pump and the abs block.

What do you mean by locks up?

Yes, very strange, been searching for others with same lock up of all brakes randomly and only a few have had same experience. They will lock up at same location on my daily commute, have to release pressure at master cylinder before it will release. Brakes will be on almost 80% while when trying to brake, I only have 50% brake pedal. Searched high and low for answer, only possibility is air in system somewhere, probably ABS, so will do another pressure bleed with diagnostics running through sequence.

Lock up to me means the wheel stop tuning and you skid to a stop.

What you are describing sounds like and automated panic stop kicking in. You press the brakes to stop and it stops "really hard" harder than you indended.

I think I the system uses the pressure sensor in the brake system to determine when to apply the panic mode. Determined by how quickly the pressure changes not how much pressure.

If there is air in the system that is compressed then stops being compressed so you hit oil, like water hammer in a pipe you could easily cause a spike in pressure that is considered panic stopping.

My money is on this scenario.

It's how my rear brake line split. I hit the brakes quickly but maybe 60% strength. Panic mode took over and put 2000 psi (140 bar)! And split my 17 year old pipe.

Randpm Brakes Lock Up
 

Well, just bled brakes for forth time, pedal is harder at top, but still do not get full braking power. More air was in right front line, backs had no air, and left front had none, ran 16 oz. twice and no more trace of air, but brake still do not function with full braking, maybe 80%, hard pedal now, but brakes still lock up. I was idling for 15 minutes and without even hitting brakes, it locked up solid enough that you couldn't get transmission out of park, crazy. Only way I can release it is to crack line at master cylinder as someone holds down brake pedal. Did get a wheel sensor code which sensor was replaced about 5 months ago. Will replace again, says lost connection, so maybe it is wire broken, that was a tough one to get out.

Did you use a scanner or tool that lets you actuate abs and prechatge pump?

Same here, first time to buy 5 liter can of brake fluid an I use it, the front wheel was not so bad, bur the rear was terrible, but in the end all was OK, and you are close to the end when you hear sound like waterfall when you open the air bleeding nipple.

Did you ever resolve this locking brakes problem


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in response to you question on "What were the codes?"

Crickets

FYI - After my brake overhaul this June, after 15+ years the master cylinder went toast, I had no pedal pressure no matter how much bleeding I'd done, barely limped it to the shop - they had to replace the Master (I brought the ZF part or whatever brand that was OE equivalent) and had to do full bleed procedure on DSC as well with ISTA/P -



Impressive that the master lasted 15+ years considering it sits in hydraulic fluid all the time. I was told its common on the older bimmers that the seals just don't hold the pressure after a certain amount of time or miles etc (and I did not own it the first 8 years of its life)