E53 - Brake bleeding issues
 

Hello,

My X5 4.8is suffered from the "vacuum pump seal failure, oil in brake booster leading to brake booster failure" issue - I changed the booster with a new unit and re-used my Master cylinder. I got everything back together and no matter how much I bleed it (I'd have bled the system 3-4 times over 4-5 days) I can NOT get the pedal to firm up. It feels very, very soft. I do not have a pressure bleeder, so I am using the pedal to the floor method. Here's what I do:

I have used ISTA-D and done the bleeding with the ABS block as well by cycling the pump - still no go. Pedal soft as hell, goes all the way to the floor.

- Ask my helper to press pedal 5 times
- On the 6th time, hold the pedal to the floor
- Run the "ABS Bleed" procedure in ISTA-D
- I crack the bleed screw (1/4 turn or so) with clear tubing attached to nipple
- Close the bleeder screw
- Ask my helper to release pedal

I repeated this multiple times per corner until no dirty fluid nor bubbles were coming out. I bled in this pattern: Rear Right, Rear Left, Front Right, Front Left.

After doing all this I had absolutely NO firmness return to the pedal; So I thought I wrecked the master cylinder and got a new one and changed it out. After bleeding, there is still NO CHANGE in the pedal feel.

I am out of ideas at this point - I don't believe I have a fluid leak since I'm not losing any fluid (level stable). I am using DOT4 fluid.

The car is parked on flat ground. I have read that jacking up the rear may help but I can't see this helping - the highest point on the master cyl when the car sits flat is the rear port, so any air should be getting pushed out of that?

Never done this before - am I doing something wrong here or is something else broken? Car was FINE before I started this (with the exception of a broken brake booster making the pedal super hard).

I have just found this post on a uk forum(xdrivers) and this is a quote from it.
"well had a good conversation with a newly opened indy to me (hes just resently parted from main dealer after 9 years and is 40miles closer than where i was going and 3miles from my work :D ) he said hes 99% (seen 5 x5s sent to him the same as mine) sure that what weve done is forced the seals on the master cylinder inside out from bleeding the brakes by pressing the pedal to the floor 100s of times, so ive ordered a new master cylinder (£55 motor fators) and he said to fit this and then bleed from the beging with the pressure bleeder which will take a fair bit of time! anyway today they have got alot worse with use but the fluid level is exactly the same so no leaks, he said that when the seals have been poped just the front calipers work. However when i asked to book it in with him he said it was a simple job for my bro who did all the new brake pipes and in his explanation he never menchioned anything about laptop for abs unit, last time we bled it running so the abs etc was powered up! also there is no abs brake function on inpa and it has everything else. i could be wrong and my brother is going to phone him when he does it. oh well get the e46 out for some fun!"
Link to the full post.
brake bleeding

I went through the same thing, it wasn't until I finally sprang for a pressure bleeder that I was able to get the job done. I think it's the servos in the ABS block that just don't like the pressure being taken off of them while bleeding.

I, as you did, bled mine a half dozen times with a partner and never for pedal - 15 minutes later, with the pressure bleeder... pedal was awesome and I was done.

If you can barrow a pressure bleeder definitely give it a try, I've never seen the "press and hold" method work on an X.

Good luck!


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I have a pressure bleeder on order... will give you guys an update once I get it.

I have spoken to a lot of people and there is a ton of conflicting information. I've got people swearing on a stack of bibles that they managed to get E46 cars bled by just stomping the pedal and not bothering with cycling the ABS pump at all.. others claiming it can't be done without the software to cycle the abs pump.

Who woulda thought something so simple would take so long?

Heard that - you will get there, I've been through it as well.

I can say all I did was open the ABS block and bleed, I never cycled the pump and I had no issues.

You will be amazed with the difference in using the pressure bleeder the pedal should come right up for you.

Keep us posted [emoji106]


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E53 - Brake bleeding issues
 

The "stack of Bibles" folk just never had air where it's not supposed to be. As long as air is only in the lines downstream of the abs of course you can use the buddy system for bleeding. Brakes don't circulate the fluid there is only one line to each wheel so the fluid probably goes a couple inches back and forth under normal use.

I bought a pressure bleeder for the eventual swap of fluid. Turns out I'll need it for replacing my rear brake lines first. Glad I already had it on hand though.

My pressure bleeder finally arrived - it's a Schwaben Compact bleeder.

I spent a couple of hours on it, had some issues with the bleeder as first it wouldn't seal properly around the reservoir (which I resolved with some teflon thread tape) and then it also seems to leak around the fitting which has the gauge on it (but this is a problem for another day).

Anyway I have made significant progress now. A ton of air came out of the rear right and front left calipers, it was very very frothy. I bled probably 2 liters of fluid through the system.

The pedal is a LOT harder but still not quite where it was before all this mess started. Obviously I need to bleed it a bit more which I will do later this week and report back. But it's looking good thus far.

If air got in the ABS block or the pre-charge pump, you need the right tool to engage then to finish bleeding. There should be a big rubber disk to seal the air over the reservoir and for the other side thread tape should resolve. I seemed to have lucked out and no air got in when. I replaced both rear lines but there seems to be a tiny bit of air in the lines I can feel a bit of compression nothing I can't life with until I do a full exhange of fluid that is already planned.

What is the "right tool to engage them to finish bleeding"? I have used ISTA-D to do this so far, and I pressurize the system from the reservoir cap to 20 PSI using my Schwaben "compact bleeder"

Anyway - I have bled 3 times now with my pressure bleeder. Very little air is coming out and there is absolutely NO improvement. Pedal is somewhat hard with car off, but with car on pedal is absolute mush.

Say pedal at its rest position is 1, and pedal at the floor is 10,
I have NO BRAKES between position 1 and 8
Position 8.5 I have some braking
9.5 Brakes are locking solid - enough to activate ABS.

Where to next? Really looking forward to getting this fixed. Car IS drivable at this point, but the first 85% of the brake pedal travel doing NOTHING isn't exactly confidence inspiring!

E53 - Brake bleeding issues
 

The way you describe the pedal drop is already exactly what it feels like when one front back circuit is open to the atmosphere. You said that you let the air out with your NT510 or equivalent?

If you aren’t spraying fluid out the front or back circuit the air must be in the pre-charge pump or the ABS block


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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)

Been searching every forum for answers, no one has had issue like this, or the couple I did find did not post the solution, so with only the brake booster left to change, will get around to it and let everyone know in case you experience this crazy issue. The only code I ever got was front right wheel sensor, replaced, no difference, then had pressure sensor code, replaced, no change, but no more codes. Was going to buy latest BMW diagnostics to see if any hidden codes show up that my scanner does not show. Anyone know if all BMW interface cables are the same, or any suggestions, had only downloaded software to date. Parked car for now.


Funny thing, brake pedal is harder now, squeaks and airy hisses now when I press pedal hard to stop, so this leads me to believe brake booster was going bad little by little, pinched of vacuum hose which should have isolated problem, as in, the pedal was hard to push, but still locked up the same, so I did not think it could be brake booster initially, but that was before squeak in brake pedal and hissing sound, so hope that is it.

See this video:

https://youtu.be/G95-S9i40R8

Car with two bad check valves in the master cylinder caused all four brakes to lock up.


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Did you remove the bleeder screws and inspect them for corrosion? Put teflon tape on the threads?

https://www.youtube.com/watch?v=_LLJXUbQkdA