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Old 03-01-2011, 01:07 AM
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Yorgi Yorgi is offline
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Location: Toronto
 
Join Date: Mar 2005
Posts: 3,491
Mein Auto: '04 M3 / '06 650i Cab
G. Front Brake Pad Change Steps:

G1. Remove front driver side wheel
While the car is still on the ground, use a breaker bar with a 17mm extended socket to loosen the 5 wheel bolts. Break the bolt loose using a star pattern then gently re-tighten to the point where the bolt can still be removed once the wheel is off the ground.
If you have wheel locks and don’t know where the key is, check under the trunk mat where the battery and tools are located which is the standard storage location.

TIP: Cover the socket with black tape to prevent marring the wheels.



Engage the parking brake and chock the rear wheel on the opposite side of the car you are jacking to prevent the car from moving while on the jack.

Raise the front wheel using a hydraulic jack on the front left jacking point. See IMAGE #05.

Use a “cross wrench” or cordless impact wrench to fully remove the 5 wheel bolts. If the wheel is stuck to the hub after removing the 5 bolts, use a rubber mallet to hit the outer edges of the wheel until it comes loose. You can also sit in front of the wheel and use the heel of a running shoe to kick the outer edges of the tire until the wheel come loose.

TIP: During removal of the last bolt, press the wheel against the hub to prevent it from falling off the hub. You don’t want the wheel falling and hitting the brake caliper on the way down.



G2. Remove Spring Clip
Use a large blade screwdriver or small pry bar to remove spring clip from caliper. Pry the middle of the clip horizontally back towards the rear of the car until the retaining lug in the middle of the clip is exposed, then pull the clip towards you.



G3. Remove Guide Pins
Pry off the two plastic caps covering the guide pins. See IMAGE #7.



Using a 7mm hex socket, remove the upper and lower guide pins.




G4. Compress Piston back into Caliper
The piston must be fully pushed back into the caliper to make room for the thicker replacement pads. You also need to push the piston in to get the caliper off the carrier if there is a wear lip on the outer edge of the rotor.

Place an 8” C-clamp as illustrated in IMAGE #10. Be careful not to pinch wires or the bleed valve at the back of the caliper. Tighten the clamp until the piston is fully seated in the caliper. There should be only mild resistance as you tighten the clamp, if not check the positioning of the C-clamp.

TIP: Keep an eye on the brake fluid reservoir for fluid levels before and after each piston is compressed. If the fluid level rises to near overflow remove some fluid from the reservoir. Brake fluid is an excellent paint stripper and will severely damage paint if spilled. See Section J below for details on how to gain access to the brake fluid reservoir; it’s buried under the cabin air filter.



G5. Disconnect Brake Pad Wear Sensor (Front Left and Rear Right wheels only)
BMW TIS Note:
The brake pad wear sensor must be replaced once it has been removed (brake pad wear sensor loses its retention capability in the brake pad)

If you are a die-hard believer in BMW’s TIS recommendations, then always replace sensors when doing brake pads.
I examine the sensor for wear and if it’s in good condition I reuse it. It is still a very good idea to have new sensors on hand in case you break them during removal. They can get brittle over time.




Follow the sensor wire back to the enclosure. Open cover of housing and unplug old sensor and replace with new sensor. There is a small push button at the base of the plug that must be pushed to release the plug. Use the old sensor wire to route the new wire back to the caliper. Do not install the “green” end of the sensor into the pad at this point.







G6. Remove Brake Caliper from the Brake Carrier and hang it from the suspension spring
Wiggle the caliper off the carrier by pulling towards the back of the car. Never let the caliper hang by the brake line - you could damage the lines which may result in bake failure. See IMAGE #19 for an example of how to hang the caliper by the suspension spring. You can also place the caliper on an upside down bucket or other suitable stand.




If the caliper does not come off easily the piston is probably not fully retracted. Repeat Step G4 to ensure the piston is compressed.

G7. Fully compress piston back into caliper if necessary
Once the caliper has been removed look at the piston and confirm it is fully compressed. If not use the C-clamp to push on the inner brake pad until the piston is fully retracted. To prevent damaging the piston, NEVER push directly on the face of the piston, always use an old pad or even a block of wood between the clamp and piston face.



G8. Clean brake carrier, caliper and guide pins. Inspect condition of piston rubber boot.
Remove both brake pads from the caliper.

Examine the condition of the rubber boot and piston face. If any rips are visible in the rubber or if the piston face contains heavy gouges or a large amount of rust order a caliper rebuild kit from BMW. It is important to thoroughly clean the surface of the piston and the inside of the caliper directly across from the piston. These two areas contact the backs of the pads and if they are not clean and smooth brake squeal can occur.

Guide pins should always be removed and thoroughly cleaned to ensure smooth operation of the caliper. The caliper slides on these pins and will bind if they are overly dirty resulting in rapid pad wear and possibly squeal.

DO NOT grease the guide pins. Unlike other cars which have metal-on-metal pins BMW uses a rubber-on-metal design that will bind the calipers if grease is used on the pins.

BMW TIS Note:
Replace guide screws which are not in perfect condition.

If you cannot get the pins clean or if you notice groves in the pins once they are cleaned replace the pins, they are not expensive.

Cleaning guide pins and the caliper-to-pad contact areas is dirty work but failure to do this will contribute to the likelihood of brake squeal and rapid pad wear. Dirty and binding calipers are a major cause of squealing.




TIP: Use brake cleaner, wire brushes and an old credit card to scrape off deposits on guide pins.

I use small brass brushes to clean the caliper-to-pad contact points thoroughly. A small blade screwdriver can be used with light pressure to scrape off large deposits. Spray brake cleaner fluid liberally as you go. See IMAGE #21 and IMAGE #23 for a before/dirty and after/clean caliper and pins.



TIP: Place newspaper under the caliper to catch brake pad dust/grime that falls during cleaning. It is also a good idea to wear a face mask and eye protection while cleaning the calipers since quite a bit of dust can be kicked up if the calipers are very dirty.


G9. Check Brake Rotor thickness and runout
The minimum allowable rotor thickness is stamped on the rotor hat. See IMAGE #24
Use a brake rotor vernier caliper (available on eBay for $30) to measure rotor thickness. A brake rotor vernier caliper will reach over any outer lip caused by worn rotors. You can also use a micrometer with a 1”-2” range to measure rotor thickness. As a workaround you can use a standard vernier caliper with two spacers placed on each face of the rotor then subtract the thickness of the spacers to get your reading.

If the rotor is below the stamped minimum then the rotors must be replaced. See Step G10.




OPTIONAL: measure rotor runout
In addition to thickness, rotors can be checked for runout (warpage). A dial indicator with magnetic stand can be found on eBay for ~ $40. Large steel surfaces are rare on the 6er, so I used the carrier for the magnetic base. A stand with a clamp vs a magnet base might be preferable.



G10. OPTIONAL – Replace Brake Rotors If Necessary
Replace brake rotors if thickness is found to be below the minimum thickness stamped on the rotor hat. Always replace rotors in pairs.

Remove the two caliper carrier bolts using an 18mm socket or 18mm wrench and remove carrier from steering knuckle.



TIP: If you are removing the carriers for a rotor install, clean and lube carriers while they are off the car.



Remove rotor retaining screw from rotor with a 6mm hex socket. Keep pressure on the rotor with one hand to prevent it from falling off the hub while loosening the screw.



Pull rotor off hub. If it sticks use a rubber mallet on the rotor hat to loosen the caliper. Don’t hit the rotor ring with the rubber mallet.

Clean the face of the hub with a wire brush. Debris on the face of the hub can cause wheel vibrations or a warped rotor feeling when braking.



If retaining screw is rusty replace it. Seized rotor retaining screws are a common problem and will require drilling out if they get bad. If I see any rust at all on the retaining screw I replace them. At $1 it is cheap insurance against seized screws.



Install new rotor on hub. Use anti-seize compound on retaining screw threads and torque to 16 Nm (12 lb-ft).



Install caliper carrier and torque bolts to 110 Nm (81 lb-ft).

TIP: If you are using anti-squeal paste on calipers, see IMAGE #38 and apply paste now before installing the carrier.
__________________
Straight lines are for fast cars...turns are for fast drivers
'04 M3 - track
'06 650i Cab - daily driver
'02 Highlander - kid hauler
'01 330Ci - winter beater


Last edited by Yorgi; 03-01-2011 at 01:30 AM. Reason: formatting
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