2002 BMW 330ci Brake Booster and Master Cylinder Change

How to change an e46 Brake Booster and Brake Master Cylinder. Note that the Brake Booster change is very involved as it requires you to move the DSC controller out of the way in order to remove and install the booster. Professional Labor on a job like this is quite lengthy (why the cost to change it is high), so you want to make sure that your brake booster is indeed bad before you go through this. My brake booster was contaminated with brake fluid and was not operating as it should. Less expensive fixes would be to spray lubricant into the booster from the driver's compartment side or replace the check valve at the 2 o-clock position on the booster. Please note, when changing the Master Cylinder, it's always a good idea to bench bleed it first.
This job involves brake fluid, handle with care, I used DOT 4. Keep away from paint or allowing it to contact and stay on any part of the body. Clean off brake fluid immediately if it contacts your paint. Do not mix brake fluid with water or allow it to contact water.

[@Jo-gu9st]

very poor video quality

[@magincap70]

The codes or the actual problem? The codes were misfires mostly and lean fuel blah blah like ten dtc's, but it was all caused by the little o-ring that goes on the back of the master cylinder....yeah, that wasn't even there. Eventually I opened the hood and could here the brake booster hissing, so I decided to replace the booster. That's how I found the missing o-ring. Put in the new booster, replaced the o-ring, fixed.

[@PiliaeAl]

Hey man I just realised Why im losing vaccuum- I forgot th eO ring behind the master cylinder!

[@anyhootyepo654]

Good video! Thank u!

[@manzana8]

Thanks for uploading this. Helped me a lot!

[@kennyspringer7668]

Okay so I have a 02 325i with the trifecta is it easier just to change the ABS sensor or go through the DCS sensors and everything the c110 Creator is telling me which is DSC one and two also caring angle sensor internal. And abs internal fault code. But I've changed a few things a couple times and like my wheel speed sensors and it knocked out to DCS sensors I think I have false codes

[@thecurtray]

od video guy.now I will fix my daughters.how many hours maybe if you read this.good stuuf my friend

[@lhendrick1]

Dan, thanks for posting this, it helped me a bit when doing my booster replacement. By combining this with some other videos here on KZbin I got all the info I needed to do the job. Some of the gaps in your video, and the out of focus section under the dash were addressed elsewhere. Again, thanks for posting this, as it's good to get this fixed.

[@magincap70]

The codes or the actual problem? The codes were misfires mostly and lean fuel blah blah like ten dtc's, but it was all caused by the little o-ring that goes on the back of the master cylinder....yeah, that wasn't even there. Eventually I opened the hood and could here the brake booster hissing, so I decided to replace the booster. That's how I found the missing o-ring. Put in the new booster, replaced the o-ring, fixed.

[@yoshi1u2]

try disconnecting thing and plugging the vac lines to find your leak.

[@20rich02]

I have a problem. when you pump the brakes the pressure on the pedal builds up and stays if you stay on the brake pedal. When you let loose of the pedal and press it again the pressure is gone and the pedal gos almost down to the floor what could that be?? Brake booster?? Master cylinder???

[@yoshi1u2]

bleed it again

[@PiliaeAl]

Wow, just looked at when you posted this! My car has been sitting on the driveway since early December. I was looking on youtube and could not find anything like this! Thanks so much!

[@SirFixAlotAutos]

Great I am glad you liked it. The most difficult part of this is moving the DSC control unit out of the way in order to pull the brake booster out (clearance issue.) You have to be very careful with the brake lines (especially during reconnection) in order not to cross thread. Take photos before you remove so that you can reference for reassembly. Good Luck!

[@andrewl7330]

Very helpful video. I appreciated seeing the process of bench bleeding and that it is normal for fluid to run out freely from the hard line passages until you get them plugged. However, you kinda skipped over the install portion. Once you have the master back in position on the car, as soon as you pull the plug out of the passage fluid will be flowing out really quickly. No? Do we just stuff a rag down there and deal with the fact that a bunch of fluid will escape while rushing to get the hard line in there? Or is there some trick to make sure you don't dump half a reservoir of fluid while doing this dance?

[@SirFixAlotAutos]

Good question, so the master cylinder works like a piston pump, if you aren't moving the pump, there's not much fluid that passes by the piston's chamber. This is the case when you are installing it. A little will drip down when removing the caps (so keep a rag underneath) but it'll be small drips since you aren't actuating the brake pedal. Good Luck.

[@andrewlunse6283]

@@SirFixAlotAutos Thanks for responding!! I don't mean to sound argumentative, but in your video the fluid is pouring out pretty rapidly on the bench until you get the cap in. I'm currently in the middle of the master install and mine acts the same, fluid pours out very quickly if/when the ports are open after bleeding. I have seen other videos where the fluid just slowly drips out after bench bleeding, not those are other manufacturers. I have 2 E46 masters on hand and they both do the same thing, brake fluid freefall I suppose this won't negate the actual bleed results? As in - as long as the reservoir doesn't go dry during the time the ports are open, no air should be getting into the cylinder...?

[@magincap70]

Hey, thanks, your video helped me out a ton. You can get that booster out without disconnecting your brake lines though. Takes a little wiggling and I had to unbolt that abs controller but it came out fine, so if you don't need to replace your master cylinder, you can do it without bleeding.

[@thecurtray]

magincap70 may I ask what issues you had to change only that.he said the master can leak inside booster and causes vacuum to run anywhere.thanks alot

[@magincap70]

The codes or the actual problem? The codes were misfires mostly and lean fuel blah blah like ten dtc's, but it was all caused by the little o-ring that goes on the back of the master cylinder....yeah, that wasn't even there. Eventually I opened the hood and could here the brake booster hissing, so I decided to replace the booster. That's how I found the missing o-ring. Put in the new booster, replaced the o-ring, fixed.