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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 10-13-2012, 06:10 PM   #81
ttrinh9
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I re bled my brake lines and tapped the dsc module lightly, pressurized the system and Waited a few minutes before cracking the bleed valve. My brakes do feel a bit more firm. I did this procedure twice. I'm going to drive around a few day and brake hard to release air from the abs, then bleed the lines again to be sure. Thanks!!
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Old 12-11-2012, 02:43 PM   #82
turnerk2
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Quote:
Originally Posted by Kris.R View Post
So I went through several of threads trying to find a cure for my issue. A brake pedal that would make a whistle type sound when the brake was applied and released. Everyone that had success with the noise being gone stated that the dealer changed the brake booster under the CPO and the sound went away. Since a brake booster is a pain in the ass to overhaul and wouldn't even seem that it would be the brake booster itself made me think that it was much more simple than that. Well, I certainly did find out that it was much more simple than that.


Parts to Purchase:
You will need part #4 and #5 from the diagram below.
The part number for #4 is 34336765316 (Gasket)
The part number for #5 is 34331160183 (Non-Return Valve)
Both parts cost around $20 from the dealership.


You will need to purchase a hose clamp like the one below.


Replacement Procedures:
- You will need a pair of plier cutters to cut the old clamp.
- After you have removed the old clamp, gently pull on the hose with the Non Return Valve connected to it and out of the brake booster.
- Now take a pair of adjustable pliers and clamp the old Non Return Valve and twist left to right while pulling it up and out of the hose.
- Once you have accomplished that, insert the new Non Return Valve by hand into the hose.
- Next, you will need to replace the Gasket on the brake booster from where you pulled the Non Return Valve.
- Once you've done that, go ahead and plug the Non Return Valve into the Gasket hole and clean up.

Now start your car and pump the brakes, guess what? No more whistling from the brake pedal!


*Everything provided in this DIY is at your own risk and I am not in any way responsible for your mistakes or broken parts resulting from non experienced persons.
do the brakes need to be bled following your procedure? i'm dealing w the same issue. thanks in advance!
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Old 12-11-2012, 02:55 PM   #83
turnerk2
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Quote:
Originally Posted by buhddy View Post
This seems to be the right direction for my issue. Haven't tried it yet, but I did remove the check valve, blow silicon and compressed air through it, and it seemed to be working. Also got some silicone spray on the check valve gasket. But it must have improved the seal because now it only whines for a moment after letting off the brake, instead of constantly whistling. I think a new valve and gasket are in my very near future. I'd hate to think it was a booster, as the brakes are functioning flawlessly. Thanks for the reply!

I have read elsewhere that there is a gasket on the firewall side that can get torn as well. As I was under the dash pushing on the brake pedal, the noised seemed to be associated with certain spot on the pushrod to the cylinder more than anything else. Which sounds like seal that's just worn or maybe a slightly thinner part of the pushrod from wear allowing a small gap from the seal. Seems like a waste to have to replace all that and bleed the breaks if that seal is the only culprit. Anybody have any luck replacing the inner seal without removing the mastercylinder? Is it even possible?
^bump
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Old 12-12-2012, 04:32 PM   #84
NC BMW fan
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There is no way to replace the gasket on the booster while its on the car. I'm not even sure if its repairable at all. On e you get the booster off to look at it, might as well replace it.
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Old 12-12-2012, 09:09 PM   #85
turnerk2
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Originally Posted by NC BMW fan View Post
There is no way to replace the gasket on the booster while its on the car. I'm not even sure if its repairable at all. On e you get the booster off to look at it, might as well replace it.
NC good point, once I get a look at it I'll be sure to post what I come up with, hissing sound at pedal is driving me bananas..
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Old 04-22-2013, 08:02 PM   #86
Sequel95
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Replacing my brake booster right now

My 2003 330ci had the whistle when the brake pedal is slightly pressed and seems to start when the car is warmed up. I ordered a new brake booster for about $179 and also ordered the connector discussed in this thread. So far so good- the old brake booster has been removed and replaced, but I stripped the fastening screw for the brake fluid reservoir when replacing, so had to remove the master cylinder again and will try to remove screw. New screw is on order. I had to remove the DSC unit to get the brake booster out. I am hoping I don't get the pedal to the floor problem that will require a tow to the dealership. What do you think is the % of cars that need the BMW system to bring the brakes back to life, notably after air has been introduced into the brake system...

I will report back after everything is back together. Good thread here. Thanks.

A few weeks ago I replaced the oil separator and all connected hoses. Big project but I watched the BavAuto video and it made it much easier. It is a slow project, so take your time if you do it. This brake booster job is now bigger than the oil separator replacement!
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Old 04-22-2013, 09:18 PM   #87
NC BMW fan
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If you had to remove the DSC, you will (or did) have to bleed the system. That should keep you from having to go to the dealership. If the pedal is soft, re-bleed to get rid of the air in the lines. Once you have decent pedal response take the car where you can do a "panic" stop. That will trigger the ABS pump. That would push any remaining air from the DSC. The warning lights will go off when the air is gone.

If you've changed the booster, the hard part is done!
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Old 04-27-2013, 11:46 PM   #88
Sequel95
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Success! I finished the brake booster replacement today. Ended up bleeding the brakes twice to firm up the pedal and I am happy to report no more whistling brake pedal. One thing I would add: if you are thinking of doing this project yourself, don't be dissuaded by comments like, " I would never do this again." Each of us has different skills and patience. If you have lots of patience and the time, you can do this project. Just take your time!
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Old 06-06-2013, 02:22 PM   #89
bswurtz
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I think I have the same problem, but I haven't seen anyone mention any check engine lights associated with this problem. I have my check engine light on and need to get it cleared to register the car. 2 different shops have said it's the booster, but I've seen a whole bunch of posts on here with no mention of any check engine codes. I don't want to go through cost and effort to replace booster and still have check engine light on. Any of you have code that went away from replacing booster, or is the check engine unrelated? Brakes still work fine, but definite air leak from booster area.
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Old 06-06-2013, 04:10 PM   #90
Itzed
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In my experience, CE lights are almost always related to issues that could possibly affect emissions, and a brake issue would not do that.
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Old 06-07-2013, 02:17 PM   #91
NC BMW fan
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Quote:
Originally Posted by bswurtz View Post
I think I have the same problem, but I haven't seen anyone mention any check engine lights associated with this problem. I have my check engine light on and need to get it cleared to register the car. 2 different shops have said it's the booster, but I've seen a whole bunch of posts on here with no mention of any check engine codes. I don't want to go through cost and effort to replace booster and still have check engine light on. Any of you have code that went away from replacing booster, or is the check engine unrelated? Brakes still work fine, but definite air leak from booster area.
What are the CEL codes you've gotten? They may or may not be associated with the booster at all. If the shop you took it to didn't tell you go to one of the auto parts stores. They can check codes but it will be very generic description. At least it gives you a starting point.

I also had CEL codes that were O2 sensor related. I had a software update done and codes cleared. It has never come back on.
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Old 08-13-2013, 03:48 PM   #92
LaRouge
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my experience replacing the booster

Thanks to all for tips. I found I absolutely could not remove the booster without removing both the ABS unit (push brake lines toward the front of car) and the black plastic cover for the computer. Also, it was much easier to work in the interior where the booster attaches to the brake pedal once I removed the driver's seat. I completely removed the aluminum frame that holds the pedal to the underside of the dash (i.e., I removed the third nut). Once back together, I started bleeding it by filling the reservoir half full with Ate super blue, pressurizing it with my pressure bleeder empty (i.e., no fluid in the pressure bleeder), tapping the ABS lightly, then, one at a time, cracking open each of the two connectors from the brake master cylinder at the ABS block (V and H) until blue fluid flowed without bubbles (blue is very easy to see on the aluminum). Be sure to rinse with clean water. Then I filled the bleeder with a quart of Valvoline clear fluid and bled the brakes. The car was quite driveable, but brakes were a tad spongy, so I bled it again with the remainder of the quart of super blue. The blue vs clear fluids made it easy to tell when I'd bled enough, saving an extra quart of each. Next time I'll have 11 mm and 12 mm crowfoot flare wrenches on hand.

I guess I'm slow--especially in 100 degree heat. The procedure took me more like 5 days--certainly a long ways beyond 5 hours! That included a trip to Ace for a tap to re-thread a messed up bolt hole for the seat. I'm wondering if the leaky booster was also responsible for the various misfire and O2 sensor codes I've been getting the past few months. Also, just as a test I didn't replace the valve where the hose connects to the booster, and it works fine.
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Old 08-13-2013, 03:50 PM   #93
LaRouge
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I forgot to mention, after the initial bleeding, my wife hosed down the street while I did a series of ABS stops from about 25 mph.
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Old 08-14-2013, 12:56 PM   #94
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The misfire you talk about...do you get that around 3500-4000 rpm? I had a "hesitation" around there and 02 codes. It turned out to be a needed software update (look for topics on this site). After the update and cleared codes car ran better than ever. A good indie garage can do the update for around $100-$150.
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Old 08-14-2013, 02:14 PM   #95
LaRouge
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I meant misfire codes; maybe I mis-spoke. Check engine light came on and with my Peake tool I got codes: 8 (Mass air sensor), 53 (Crank Sensor), F4 (Flywheel adaptation segment timing faulty), E4 (O2 sensor adapt. limit cyl 4-6) and E3 (same, cyl 1-3).

Cleared codes and got E4 and E3 two days later.

Codes were obviously garbage, but indicated something was wrong that the computer couldn't directly measure, i.e. vacuum, hence the booster. At least that is my almost completely uneducated opinion.

By coincidence, the car did go into limp-home mode back in March. It had been throwing a bunch of codes (FA F2--maybe that is when I got a misfire code). I replaced the fuel tank breather valve p/n 13 90 1 433 603 and the codes disappeared until the booster started hissing.

After replacing the breather valve I had to deliberately do the drive cycle routine because a few hundred miles over a week around town wasn't enough to pass emissions.

Nice to be done with all that. I hope.
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Old 08-14-2013, 03:26 PM   #96
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I'm not familiar with Peake codes, your situation sounded similar to mine but with more detail now it doesn't. New O2 sensors could fix it but don't replace anything based on my assumptions.
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Old 08-14-2013, 03:54 PM   #97
LaRouge
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I don't think there is anything left to fix. Peake codes refer to the R5/FCX-3 reader, which I have used a dozen times since I finally bought one last year. My guess, probably originating with discussions with brother-in-law BMW indie mechanic, is this: a vacuum leak can trigger spurious codes (02, crank, MAF etc); therefore a bunch of unrelated codes at once indicates a likely, or at least possible, vacuum leak. There is no direct code for a vacuum leak, but the hissing booster was an obvious leak. I don't plan to replace 02 sensors until I get the code just for them--without a bunch of other codes. Although at 180k miles replacing them wouldn't hurt anything but my pocketbook.
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Old 12-23-2013, 10:33 PM   #98
Jsmk23
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I have the same hissing coming from behind the brake pedal and from under the hood in the brake booster.

The hissing begins as soon as i start it up. It goes away/or very light hearing if i press the pedal all the way down with force.
It gets louder if i light press it down.
It also goes away if i press down the accelerator but if i let go of accelerator even at high speeds it will still hiss.

I also noticed if Im at a stoplight at idle, the idle dips a little.
But if i pushed down the brake with force to the point the hissing goes away the idle goes up at normal.

I also have lean and misfiring codes.

I hope its not the brake booster

** Also no difference in braking/brake pedal itself.
Same as normal

Last edited by Jsmk23; 12-23-2013 at 10:37 PM.
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Old 12-26-2013, 02:34 AM   #99
turnerk2
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the source of the hissing, at least in my case, was a leaking/cracked diaphragm inside the brake booster, had it replaced, now it's fine, no more hissing. not cheap to have repaired but if you can do it yourself you'll save a lot of dough. hope this helps
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