2006 x5 brake pedal travel goes low even after bleeding.

[mendes9]

Hi all, a couple days ago "low brake fluid" message came up and noticed that it was a little low, and then pedal went lower than usual. I put in additional fluid pumped brakes but pedal still travels too far down. I tried to bleed them and notice that fluid was not coming out and fluid not leaving reservoir. A common problem on all master cylinders is the very small holes where the reservoir seals are located, become clogged clogged. I removed the reservoir and run a small wire through the holes. I then bleed the brakes again, and rear brakes some fluid came out now but still didn't seem normal, meaning the flow rate didn't seem normal. The front brakes when I bleed those fluid coming out seemed about normal, and fluid from reservoir was emptying now. Ok, I put it all back together (pain in the behind but will be much easier if I do it again). If I pumped the brakes car is off, the pedal became hard after a few pumps and was normal. Turn the car on, and while the brakes do work, the pedal is still lower than normal, yes the brake fluid level is correct. Any ideas? bad master cylinder? Note that I did remove the 2 metal brake lines, but I did re-bleed the brakes at all wheels.

[EODguy]

Did you use the purge menu in your Foxwell or INPA? If not you could definitely have bubbles trapped in the system and regular bleeding won't get them out.

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[andrewwynn]

If air gets into the abs block or the pre charge pump you need to use a tool that will engage those systems for bleeding.


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[mendes9]

Thank you, after some further reading that what appears to be the issue. I will update the thread with results.

[80stech]

The "low brake fluid" warning comes on long before the brake fluid is low enough to cause problems with air and/or the pedal going low, so something more must be going on here.

[StephenVA]

Check a few things. Does you pedal hold steady under a constant foot pressure or does it slowly go down? If the later, check for brake fluid leaking under the driver's seat (under the car not in the car) where the lines tend to rust away. There is a large black panel that covers that area so the line are up inside the frame rails and are trapped in a high moist area. The line covering is of a poor design so they all will rust away in any salt, high humidity region. Ask me how I know.... Mine died at 60K sitting under a cover. Never driven in the winter and always washed and clean.

Brakes not bleeding in rear. Note: this is a given if you have the above problem as the ABS unit thinks you have a leak.

The activation of the ABS bleed procedure will allow the solenoids (?) to open allowing fluid flow to each caliper. The RR is the longest line so it takes a awhile to clear all the air that is trapped. Plan on three/four Qts.

[mr_robot]

Also it's worth checking the vacuum pump the the right cylinder head if you have a N62, Its connected to the booster pump and if it leaks oil it can cause brake pedal problems.