P0171 is bank 1, not bank 2.

Test the brake booster for leaks. Google/youtube/search for how to.

 

Roger that. Im not sure why I even included the P-code number. I edited my post and took it out.

 

Also search our DIY Guides forum. Lots of good stuff in there.

DIY Guides

Do it yourself guides for E46 repairs/mods

www.e46fanatics.com

 

I took the panel off at the steering column, and was able to see a fluid leak at the union of the shaft and boot. And the sound is definitely coming from this location. It's not the blue/black MPG vacuum line, like I was hoping. In the video below, I'm moving the brake pedal a little, and you can hear the vacuum leak get louder when I'm off the brake, and go away as I dress the brake. Although it never fully goes away.

 

I am surprised if the leaking fluid is brake fluid from the master cylinder at the front. It is almost impossible to pass through the booster diaphragm and into the pedal side.

The pressing down pedal activates two valves:

• one valve to seal the small path connecting the two chambers together so the front chamber doesn't loose the vacuum
• one valve to open so ambient air can enter the rear chamber. I think this valve is leaking.

 

Being in America you may be able to find a business that can recondition the booster as not sure the offending seal could be DIY replaced. If it can't be DIYed or reconditioned then those vac cans are stupidly expensive from BMW.

 

FCPEuro has an "OE" ATE brand brake booster for under $200. I'm just wondering if it's necessary to replace the whole booster, or can this be fixed with less trouble and effort.

 

Wow, FCPEuro for the win. I looked over here in Australia and was looking at around AU$1600 so even with shipping from USA that ATE item is what I'd be buying

 

I have never replaced a brake booster or a master cylinder. But I think you have found another vacuum leak. I hope it solves your issue.

I believe at a minimum you should replace the brake booster and that ATE unit from FCP looks like the right thing to buy.

However, you should do some research on whether you need to replace the master cylinder also. Your video seems to show brake fluid on the booster bellow...According to the link below, that should not happen and that you may have to replace the master cylinder and/or a seal between the master cylinder and the booster.

Brake Booster Leak - Fixable?

Brake Booster Leak - Fixable?

www.e90post.com

Have a search...

 

You know the picture of the Brake Booster on FCP includes a seal, maybe that is the seal to keep brake fluid from the master cylinder out of the the booster.

 

Normally on any MC the seal for fluid is internal to the MC. That O ring is likely just to keep crap getting between the MC and booster.

 

Thanks for the replies. I'll order the ATE unit.

 

To close out this thread, I replaced the brake booster with this ATE unit.

I used the 50sKid method from this video:
"BMW 330i 325i E46 Brake Booster Replacement DIY (No Bleeding Required!)"

The two things I had to do differently from the video:

1) Remove the bracket off the bottom of the DSC. The bracket is held on by 3 x 10mm bolts. This gave me the clearance to get the old booster out and new booster in.
2) Remove the brake pedal bracket entirely, and remove the pedal itself from the bracket.

There is an uncomfortable amount of brake line bending, but it all went back together and is functioning properly. And, the lean codes haven't come back.

 

You have come a long way man..... You were thinking about selling this car for scrap a few months ago....

 

Glad it worked out for you Plus, only a few hundred bucks for a BMW part from a reputable OE brand = winning Not for the scrappers then