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Discussion Starter · #1 ·
I have a 2001 325XI and the other day I went to brake and my brake pedal was really soft. So, I looked in the brake fluid reservoir and it was black. The brake fluid looked very burnt. After looking around I assumed it was the brake master cylinder.

So I ordered a new one and of course it was the wrong part because the 325XI has a lower connection (not sure what it is connected to). I found a re-manufactured one locally and picked it up.

After reconnecting everything, putting in new Dot 4 fluid and bled the brakes for an hour (until all bubbles were out and the fluid started running the color of the new fluid) I assumed it was all ready to go. I went for a ride and the brake pedal is still spongy.

My problem / question: I realize that I opened up the brake system so I probably have a ton of air in the system. I know I am going to do more bleeding of the brakes but how can I bleed the lower port on the master cylinder?? I feel like I could have air trapped in the lower line of the new master cylinder and cant think of a way to bleed that. If I have air in there I'd be stuck with a spongy pedal.

Any ideas?? Once I have this fixed up I took a lot of pictures and will do a DIY on the sight.

Thank you!!
 

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i hope u figure it out...and i cant wait for the DIY on the master cylinder replacement as i have to replace mine real soon.
 

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Discussion Starter · #3 ·
Well, (4) litres of DOT 4 brake fluid later I have figured it out!

1.) ABS; there are a lot people saying you have to go to a BMW dealer to pulse the ABS system. I had my BMW up on blocks and turned on the car, slightly ran the car so the wheels were spinning and slammed the brakes so the ABS went off. I did that and bled each brake individually.
2.) Bench bleeding of the master cylinder: After (3) litres of brake fluid, tons of bleeding on each corner I was still a bit spongy. My buddy kept saying that "you should have bench bled the master cylinder". So, I took off the hard lines again, hooked up the bleeding kit and bled the master cylinder while it was on the car. And we did get a ton of air out of the system.

We then went back to bleeding the brakes again, we used up another litre and the brake felt great! So I will put up the DIY and pictures tomorrow. My wife's car is back and for a 2001 car it brakes like a race car, just snappy, hard, perfectly progressive brake feel!

DIY tomorrow!
 

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Well, (4) litres of DOT 4 brake fluid later I have figured it out!

1.) ABS; there are a lot people saying you have to go to a BMW dealer to pulse the ABS system. I had my BMW up on blocks and turned on the car, slightly ran the car so the wheels were spinning and slammed the brakes so the ABS went off. I did that and bled each brake individually.
2.) Bench bleeding of the master cylinder: After (3) litres of brake fluid, tons of bleeding on each corner I was still a bit spongy. My buddy kept saying that "you should have bench bled the master cylinder". So, I took off the hard lines again, hooked up the bleeding kit and bled the master cylinder while it was on the car. And we did get a ton of air out of the system.

We then went back to bleeding the brakes again, we used up another litre and the brake felt great! So I will put up the DIY and pictures tomorrow. My wife's car is back and for a 2001 car it brakes like a race car, just snappy, hard, perfectly progressive brake feel!

DIY tomorrow!
How do you beed the master cylinder? I just replaced all the calipers bled the lines and the ABS but the pedal is still mushy
 
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