Brake pedal to the floor in E70

[heze]

Good evening all,

I have a problem with my brakes: When the car is running, the brake pedal is going slowly to the floor... Please read the following part for the complete history:

- I bought this car with major electrical issues, so I never drove the car and I don't know whether this problem was already there when I bought it...
- My DSC unit was faulty (ECU faulty). I replaced the DSC with another used DSC.
- I bled the complete brake system with two man method. Pedal rock hard after bleeding.
- As soon as the engine was able to run again, I discovered that the pedal was slowly going to the floor.
- I replaced the master cylinder (for a new one) because this is useally the problem. Bled the system again, and no change in behaviour.
- I suspected the DSC to be faulty. Changed the DSC for another one. Bled again and still the same behaviour.
- Tested the master cylinder by plugging the connections to the DSC and press the pedal with running engine. Pedal was hard en did not go to the floor.
- Reconnected the front line to the DSC again. Bled the system again. Pedal did go to the floor again but after 10 attempts the pedal became harder and became almost acceptable, but a bit mushy.
- Reconnected the aft line to the DSC again and bled the system again. Now the pedal went to the floor again, and this did not change after multiple attempts.

I bleed with air pressure to the reservoir and a canister to the bleeding nipples. I also did the bleeding procedure in ISTA (operating the ABS valves while bleeding).

As you can see, I tried a lot to get rid of this problem, but I still cannot figure this out... I suspect that there is still air in the system, but how can I get this air out?

I read more storys about this problem, but never saw the real solution to it. Some people are still driving around with this problem.

Thanks in advance and best regards
Hendrik

[SF07e70]

subscribed

I had my brake pedal go all the way to the floor after no braking in a snow shower. It happened after no braking for about an hour due to very light traffic. Since then, I found myself testing the brakes every 15mins or so to make sure there was pressure.

[h16bill]

Did you figure it out? I have the same issue after changing the front calipers. I suspect its air in the DSC unit.

cheers
Bill

[beetle6986]

Originally Posted by h16bill

Did you figure it out? I have the same issue after changing the front calipers. I suspect its air in the DSC unit.

cheers
Bill

This is normal the first few times you pump the brakes after changing pads. After pumping the pedal a few times they should go back to normal. Changing pads doesn't introduce air into the system unless you disconnect the calipers for some reason.

[Skers 05]

Have you tried ISTA to run the bleeding routine?!

[heze]

Good morning,

I left it as it was. New master cylinder and replacement of the DSC did not solve the problem.

Half a year later the car was ready for the yearly examination by the garage and was approved to be road legal. During driving it is not a problem, but when you press the brake very hard during standstill, the pedal slowly moves to the ground (in about 20 seconds).

Since it passes the garage's test, I will leave it as it is.

I also read that one of the 4 brake hoses could be the problem. When the sthrengthening fibers inside the hoses are broken, the hose can stretch or swell during hard braking, causing the pedal to go to the floor without a visible oil leakage. Maybe you can check this.

Did you bleed the system after changing the calipers? This always needs to be done! When you don't do this, exactly the symptoms as you describe will happen.

Best regards Hendrik

[Entr0py]

Get 4 pairs of vice grips and clamp off the 4 hoses.
If the pedal holds high and hard, everything under the hood is good.
Have someone take off the vice grips 1 at a time while you maintain pressure and note the pedal height changes.
You will figure out where the pedal is going.
You did not mention the year or the miles on the calipers, that would be my guess.

Most of the time no one bothers to grease the caliper bolt sleeves, (that should slide in the caliper brackets) when they change the pads, then they seize and cause this fading pedal. You have 8 slide sleeves, 1/2 are probably seized.

I took off my calipers, painted them yellow, clear coat w/catalyst, all new hardware.
Zero problem bleeding the system.
Some nice slotted and drilled rotors, nice pads, and I have had the best brakes for 3 years/30K now.

[X5 MAN]

Entropy

That's an awesome looking ride for a 2007 X5 !!

[Entr0py]

Thanks, but it's 2011 as you know

[h16bill]

Still having this issue.

>Have you tried ISTA to run the bleeding routine?!

Yes, running the ISTA DSC bleed routine with 20lbs applied to the master cylinder cap. Might try 25lbs today. I am thinking about c-clamping the brake lines today. I have never done this because I believe it leads to rubber line failure but I am running out of ideas and the rubber hoses are cheap.

[TwinSnailz]

Do you have the stiff brake pedal after parking over night or a few hours?

[h16bill]

Any time with engine off the brake pedal is rock hard. When the car is started the pedal will slowly sink with hard pressure on it. I just tried it with the front two rubber hoses clamped off. Still does it. Need to try the bleeders to make sure they are securely clamped when I go back out. I don't want to clamp the back ones since I haven't done anything to the back.

[TwinSnailz]

Mine was the same. I had a feeling that the brake booster had failed. Previously I had changed out the whole check valve line because bmw didnt sell just the check valve itself along with the booster seal. Nothing changed. Did a master cylinder leak test by putting a flexible nylon strap down the booster vacuum hole to see if any brake fluid was leaking from the master cylinder. None was found.
I purchased a used booster from a low miles 2013 x5 along with new aftermarket master cylinder , while im at, because there was some nasty white gunk in there.
Everything is back to normal now. No more stiff pedal and sinking(which scares me the most).

I shook the old booster and there were a lot of debris which I couldn’t get out to see what it was or had failed. But glad that it was the culprit
Taking out the booster was tricky. You have to maneuver it at a special angle for it to come out because the wiper rods were in the way. Good luck with yours or anyone whole have this problem.

[h16bill]

Mine was working fine until I discovered a partially stuck caliper. After switching both front calipers I have the pedal issue. Unless bleeding the brakes can cause the booster to fail I think I have a different issue.

[deepblonde]

Originally Posted by h16bill

Mine was working fine until I discovered a partially stuck caliper. After switching both front calipers I have the pedal issue. Unless bleeding the brakes can cause the booster to fail I think I have a different issue.

Any updates? Have you managed to resolve your brake pedal sinking problem?