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Thread: The Brake Booster Job

  1. #1
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    Thumbs up The Brake Booster Job (Done)

    As you all maybe familiar with the post I made a week ago regarding the strange brake behavior I was experiencing. The Brake pedal went all the way to the floor when the pedal was pressed as a single motion.

    Based on the diagnosis of the trusted sources here, the symptoms pointed to the brake booster. There are no leaks in the brake cylinder area or at any of the brake lines at the wheels. So I decided to get Bill's (MaxLumen) Brake booster rebuild kit and give the booster a overhaul. I will also be replacing the Brake lines with Stainless Steel lines, and a new set of pads. Since I will be working on the brake system I will also flush the fluids.

    Now that I have all the things to do, I tried to look up some good instructions with pictures to do this job. Could not find a lot other than what's on Bill's site. While that is useful it was not as friendly to follow. S here is my attempt to document this with as many pictures I can take and go slow so that the next person like me may benefit from it.

    I had to change servers so here are all the pics in a single folder.

    Parts:
    • Pentosin 7.1 or 11s (A little bit may be lost during the process)
    • Brake fluid of your choice (I alternate between Motul Gold and ATE Blue so that I can visually verify the flush)
    • Coolant (A small amount may be lost)
    • 2 Rubber Grommets (PN: 34-31-1-160-133) that goes between the brake fluid reservoir and the booster (Not required but you know me. LOL)

    Tools:
    • Various ¼ drive sockets (Easier to use)
    • Flat Brade and Phillips Screwdrivers
    • Long Nose Pliers
    • Bench Vice (Nice to have)
    • 2 small pieces of wood (2"x4"x6" should do)
    • Hair-dryer or heat gun
    • Various Wrenches
      • 7mm (Brake Bleeding)
      • 11mm
      • 14mm
      • 17mm flare and crowfoot
      • 13mm flex joint

    MISC.
    • Microfiber Towels or Lint free rags
    • Rubber Gloves
    • Fender protection mat or a blanket (from accidental spill of brake fluid on paint)
    • 2 shallow medium sized aluminum foil tray or baking pan
    • 3 corks from your favorite wine bottle (to plug the coolant hoses at the Aux Water pump)
    • 2 small flat plastic containers
    • A retaining pin remover or a Carving fork
    • A small container of soapy water

    Inital Prep:
    • Set up a bench or clean work area with a bench vice
    • Set the wipers to vertical
    • Ignition off, pump brakes till the pedal gets hard to discharge system pressure (about 20 pumps)
    • Place one of the aluminum foil tray under the work area by the driver side firewall
    • Place the fender protection mat or blanket on the driver side fender and secure


    So Now the fun starts. I will take it slow and do this over the next couple of days depending on how much time I have to put in it.

    Remove interior trim

    Open hood as you will be taking the hood opening handle off.

    Pop the small black cap and remove single screw in center of hood release lever on the left foot rest and remove lever

    2 plastic screws near pedals (rotate 90 degrees)

    2 plastic screws on underside of leather trim

    2 plastic screws on left foot rest

    Remove foot rest carefully by slowly pulling towards the seat while pushing towards the center of the car. The end of the footrest has a tab that needs to be detached carefully.

    Remove the pedal base cover by slowly pulling towards the seat while also pulling towards the door. The end of the base cover has a tab as well.

    Remove the leather trim. Be careful, there are 3 Velcro strips along the console, and three retaining pins along the top (a pin popper or a carving fork does the job quite nicely)

    There is also an air duct that is in the way. It is held in place with a single screw up by the door side of the duct. Remove it..

    That's all for the day. The hard part of removing the four 13mm nuts will come up soon.
    Last edited by Ahmed303; 12-07-2013 at 03:39 PM.

  2. #2
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    Do not undo the 4 nuts untill you have removed the master cylinder and the two lines that go to the booster - the two lines into the booster are in sometimes verrrrry tight and you will need all the leverage you can get. After everything is disconnected under the hood, then tackle the 4 nuts and the pin that attaches the brake pedal to the booster. BTDT...
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  4. #4
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    Quote Originally Posted by Wuffer View Post
    the two lines into the booster are in sometimes verrrrry tight and you will need all the leverage you can get.
    +1 and use a tool that drives the walls only like shown HERE!
    to register your 8 @ www.8coupe.com!

    Best regards from good old Germany Harry!

  5. #5
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    And I would recommend disconnecting the battery. There is a thick live wire under the dash in close proximity to where you will be working. Got got a nasty zap when I was doing this job years ago!

  6. #6
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    Thumbs up

    Ahmed, good timing. I'm actually in the process of doing this myself. I have the booster out, just waiting for the rebuild kit to come in the mail from Max Lumens. Definitely, disconnect the battery, as mentioned above. But before you do so, leave the wipers in the extended position to ease the removal of the cabin micro-filter cowl. Also I strongly recommend a crowsfoot flare wrench for disconnecting the hard lines. That was the only way I could undo the booster hard-line fitting. I had no trouble with the 4 brake booster bolts from inside the footwell, it wasnt too difficult getting access to them. I did all 4 with the brake switch disconnected, but in its place. Just use a long extension for the hidden one.

    I emptied the pentosin tank and moved it aside (still attached in car), I then disconnected the hard-line fittings from the pentosin manifold and moved them aside. I was able to loosen the 2 master cylinder bolts that bolt it to the booster and wiggle the master cylinder aside. I was then able to remove the brake booster without removing the Master Cylinder from the car or disconnecting the brake lines. Its not too difficult, and there is sufficient play in the lines to push the master cylinder aside and out of the way in order to get the booster out. This way, I didn't get air in the MC and I wont have to bleed the brakes (did that few months ago). Since you will be replacing your brake lines with, it may not mater to you anyway, but its much easier to bleed the brake system with the MC intact and no air trapped inside it.

    Also, no need to remove the heater control valve, that too can just be pushed aside once you remove the cabin micro-filter cowl. This is a good time to check all your hydraulic hoses under the booster. I used this opportunity replace all of mine.

    Let me know how your work is coming along and thank you for documenting your process.

    EDIT:
    As luck would have it, I just received the rebuild kit in the mail this morning and I rebuilt the booster. Took me 2h. As others have documented, pressing the seal into the retainer was a PITA. I really cant imagine doing this rebuild without a vise,. The remaining 5 or 6 O-rings were simple enough.
    Attached Images Attached Images
    Last edited by nervnom3; 04-13-2013 at 10:14 PM.
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  7. #7
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    OK....So had a couple of hours to spend with the car and wanted to pick up the brake booster task.

    - Put the wiper arms vertical and turn of the car



    Since I had to start the car to put the wiper arms up, I pumped the brake pedal to depressurize the system again.

    - Take the plastic cover off of the Aux Water Pump. It has 3 spring clips that attaches it to the 3 Acorn nuts of the pump. I started in the back to detach the one in the middle (Driver side edge) and then the front 2 came out easy. The cover is fragile and I remember cracking one before on another car.





    - Took out the cabin air filter enclosure.



    - Tagged and detached the 2 sensors. One mounted on the pump and the other on the bracket



    - Detached the bracket by unscrewing a small Phillips head screw

    Unscrewed the large connector mounted by the battery charging port and detached the connector. There is a ring hat holds the back end of the connector to the mount.

    - Took out the 3 acorn nuts that holds the Aux pump assembly to the bracket.

    - Detached the top most hose from the pump and capped it with a wine bottle cork. I was careful and lost just a few drops of coolant

    - Detached the 2 pinch clips that hold the sensor wires to the wall between the pump and the fuse box and moved the cable away

    - Lifted the Aux pump up and away to take it off it's posts

    - Detached and capped the bottom 2 hoses, put the pump away and pull the hoses away from the work area using an elastic cord.

    - Now that the area is cleared away, unplugged the brake fluid tank cap sensor, took off the cap and screen inside and pumped out the brake fluid from the tank using a turkey baster.

    - Once all the fluid was pumped out I detached the tank from the booster assembly by pulling up and slowly rocking back and forth. If you want to reuse the grommets, be careful rocking too much side to side. Since I will be replacing these (as always) I didn't care all that much

    - Detached the electrical wire from a clip that is mounted at the joint of the assembly. There is a better picture of the clip later

    - Took out the low pressure pentosin hose by loosening the hose clamp and pulling up. I was careful to quickly slide my finger under the hose so I lost just a few drops. Capped the hose with a small ¼" X 2" wood dowel

    - Using a 17mm Crowfoot, 12 inch extension and a 3/4 drive ratchet at a 90 degree offset, detached the high pressure line. This was super tight and I don't see how this can be done without a crowfoot.

    - Detached the 2 had brake lines using a 11mm flare wrench

    Now that marks all I needed to do under the hood. You may have noticed that I had my hood up in a service position again. This position gave me more room and light to work with.

    Inside the car (again):

    - Detached the 4 13mm bolts using this long and flexible extension I made. This is similar to the setup I used for a few of the nuts when I did my intake manifold gasket job. This let me take out the 4 nuts very easy and under 10 minutes.

    - I then took out the small clip that holds the clevis pin that attaches the brake pedal to the booster shaft. I pulled and wiggled assembly a little from under the hood to loosen up the pin area and pulled the pin out detaching the assembly from the pedal.

    (This may sound crazy but getting that pin ou was the hardest part of this job so far)

    - Slowly wiggled and pulled the assembly towards the front of the car and It's out. Put in on a large foil container to drain the fluids out before I start rebuilding (Hopefully tomorrow.)
    Last edited by Ahmed303; 12-07-2013 at 03:42 PM.

  8. #8
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    The yellow paint on the bolts leads me to believe someone already replaced this once before?

    PICT1255.JPG

  9. #9
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    May have. The bolt threads also had some blue thread-locker on them. Not sure who did it or when because I looked through all the receipts from the PO and don't see this being done.

  10. #10
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    Quote Originally Posted by olinjohnston1 View Post
    The yellow paint on the bolts leads me to believe someone already replaced this once before?
    I'd say for sure, as OEM bolts should be hex head, not allen.
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  11. #11
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    Quote Originally Posted by nervnom3 View Post
    I'd say for sure, as OEM bolts should be hex head, not allen.
    HUH? The difference?

  12. #12
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    Hex head - hexagon externally.
    Allen head = hexagon internally.

    (google image search if all else fails)

    Your allen head bolts lead me to believe that the original hex-head bolts from your brake booster were replaced sometime ago by someone and marked with yellow paint markers.

    http://www.realoem.com/bmw/showparts.do?model=EG11&mospid=47330&btnr=34_0501& hg=34&fg=25

    No biggie, just sayin'.
    Last edited by nervnom3; 04-19-2013 at 10:27 PM.
    ----- Alpina supercharger parts and rebuild kits. www.b7stuff.com -----
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    e36 M3 Vert


  13. #13
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    Oh OK.

    BMW may have changed things around as well. Like the Fuel rail bolts used to be Allen but they changed to T-30. In any case there is sufficient evidence that the booster was replaced before. Mox's kit will just allow me to recheck everything and upgrade.

    Talking about the re-build I spend a little more time

    - Detached the booster from the Master Cylinder by unscrewing the 2 Allen bolts.

    - Put the Booster on it's end in a tray and turn the set screw a half turn to let some fluid drip out.

    - Place a rag under the booster and hold the booster down. Take the set screw out completely and slowly let the booster up so that the spring can come out. A lot of pentosin should come out here. Mine looked very fresh from the last flush I did.

    I left the booster on it's end for a little while thinking the internals will drop out with gravity but I ended up taking them out with a rag wrapped needle nosed pliers

    Replaced ALL (except 2) O rings even the 4 (2 round and 2 flat) on the Servo piston connected to the pedal shaft

    - The first remaining O ring is this one on the right (next to the oil seal) and I am scratching my head to figure out where it goes. Can some one tell me please?

    - The second one is this one I took out of the input shaft area and forgot the orientation of the groove of that O ring. Can someone tell me if the groove of the O ring should face the inside or outside?

    There is a chance I will be able to wrap it up soon.
    Attached Images Attached Images
    Last edited by Ahmed303; 12-07-2013 at 03:43 PM.

  14. #14
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    I am doing exactly the same job, in addition I'm doing the master cylinder too (just inspect and clean. Yes it can be disassembled non destructively). In regard to the input shaft seal in question, the grooved side faces inside the booster as the fluid pressure inside the booster will get into the groove, forcing the seal around the shaft, improving the seal. you can pretty much think this way logically with all seals of this type.

  15. #15
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    Quote Originally Posted by affa View Post
    I am doing exactly the same job, in addition I'm doing the master cylinder too (just inspect and clean. Yes it can be disassembled non destructively). In regard to the input shaft seal in question, the grooved side faces inside the booster as the fluid pressure inside the booster will get into the groove, forcing the seal around the shaft, improving the seal. you can pretty much think this way logically with all seals of this type.
    Super! Thank you.

  16. #16
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    OK a quick e-mail to Max Lumens resolved the mystery of the extra O ring. As everyone says, his kit is "Over-Complete". That O ring was included just in case I had an older style E32/E34/E28 Booster.

    With that happy note I marched along

    - I used this diagram from Martin's page to reference my reassembly

    - The new seal was pressed in. It was tight initially so I did this trick. I put the seal in a new and dry zip-lock freezer bag and put it in the freezer overnight. At the time of assembly, I took it out of the freezer bag and placed it on a dry paper towel. Then I used a hairdrier to heat up the metal cone (hot to touch but not too hot) to expand the area a little. Then I just pushed in the seal in the opening. I pushed it in using a flat piece of cardboard and my fingers and was very careful to make sure all edges went in correctly and level. (Old on the left and new setup on right)

    All other pieces were cleaned and re-assembled:

    Had a very busy weekend with the wife doing a lot of spring cleaning and shopping stuff. Hopefully, this will be a productive week for me to put the car back together.
    Last edited by Ahmed303; 12-07-2013 at 03:44 PM.

  17. #17
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    Thanks for taking the time to document this so well Faisal, I know I will be doing this some time in the future. Would you mind listing all of your sources for parts?
    I sure hope admin puts this over in the DIY archives for future easy reference.

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    Quote Originally Posted by 8Harry8 View Post
    +1 and use a tool that drives the walls only like shown HERE!
    Ooooo....these look good! What sizes do we need? I know down the line I will have to do this and will need the right tools. Plus I HEART tools


    Faisal, excellent write up my friend!
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  20. #20
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    Quote Originally Posted by IcemanBHE View Post
    Get it consolidated....and Ill stick it.
    Will do. I need a little more time to wrap it up with re-installation picture. The biggest problem with consolidation is the 30 picture limit. Even if I break it out to multiple posts, the auto-merge kicks in.

    You can consolidate and sticky this one if you like. This one is complete.
    Last edited by Ahmed303; 04-23-2013 at 08:35 PM.

  21. #21
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    OK. Wrapped it up today.

    Attached the Master cylinder to the booster. There is a small restrictor plate that goes to the front hole of the master cylinder closest to the closed end. Replaced the 2 rubber grommets on the master cylinder that connect to the brake fluid reservoir. Attach the booster and the master cylinder together with the 2 bolts and remember to attach the black clip that holds the alternator wire.

    Now slide in the assembly back to the opening. I used a small long plastic box to just hold it in place till I attach the pedal connection.

    This gave me a decent level of movement flexibility to attach the Brake pedal to the booster shaft by pushing the pedal all the way in and put in the Clevis pin and the retaining clip without breaking a sweat. After the pedal was attached to the booster shaft, I bolted the booster to the firewall as before.

    Lined up all the connections and connected them.

    Cleaned up all the parts and pieces and put them back using the opposite way I took them off.

    At this point most people will bleed the brakes, top up the pentosin and burp the coolant and be done. I however wanted to do a few extra things in between.

    Switched the 2 front rotors as they were put in the wrong way before, ditto with the rear rotors to match the fronts. Replaced all the brake pads in all corners, replaced all the brake lines with the Phoenix SS Brake lines and the 2 brake pad sensors. Then bled the brakes with fresh ATE Blue fluid. NOTE: For the brembo 4 piston BMW brakes with 2 bleed nipples, bleed the inside nipple and then bleed the outside.

    So That's a wrap. Now I have to figure out the pesky wire problem I have in this post so that I can start my car again.
    Last edited by Ahmed303; 12-07-2013 at 03:45 PM.

  22. #22
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    Excellent work Faisal - nice looking disks as well!
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  23. #23
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    Quote Originally Posted by Ahmed303 View Post
    Remove interior trim

    Open hood as you will be taking the hood opening handle off.

    Pop the small black cap and remove single screw in center of hood release lever on the left foot rest and remove lever




    2 plastic screws near pedals (rotate 90 degrees)

    2 plastic screws on left foot rest




    Remove foot rest carefully by slowly pulling towards the seat while pushing towards the center of the car. The end of the footrest has a tab that needs to be detached carefully.





    Remove the pedal base cover by slowly pulling towards the seat while also pulling towards the door. The end of the base cover has a tab as well.


    Faisal,

    Nice write-up and pictures as well. Having done this very job on my '91 last year, I must ask why on earth, you would remove the hood release lever and kick panel on the drivers side? This is not needed to do this job.

    Dan M.

  24. #24
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    Quote Originally Posted by DanMarshall View Post
    Faisal,

    Nice write-up and pictures as well. Having done this very job on my '91 last year, I must ask why on earth, you would remove the hood release lever and kick panel on the drivers side? This is not needed to do this job.

    Dan M.
    Thanks Dan. Not sure about the '91 model but in my car the black plastic pedal base cover has a downward bent edge that is covered by the top edge of the driver side kick panel. Removing the kick panel makes it easier to remove the pedal base cover by pulling that side down first to detach the tab on the other side.

    001.JPG

    002.JPG

    003.JPG
    Last edited by Ahmed303; 05-02-2013 at 08:31 PM.

  25. #25
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    Faisal,

    I think they are the same, but I had no problem removing the cover. I didn't need to remove the air duct for mine either.
    anyway nice job on the tutorial.

    Dan M.

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