View Single Post
Old 03-01-2011, 01:10 AM
Yorgi's Avatar
Yorgi Yorgi is offline
Officially Welcomed to the 'Fest
Location: Toronto
Join Date: Mar 2005
Posts: 3,650
Mein Auto: '04 M3 / '06 650i Cab
H. Rear Brake Pad Change Steps:

I will not go into the same level of detail for the rear pads because of the similarities to the fronts. The main differences are the shape of the spring clip and the fact that the outer pads do not have fingers on the back.

If you are changing rear pads only, review the front pad steps above in Section G if more detail is required.

H1. Remove rear passenger 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 retighten 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 front wheel on the opposite side of the car you are jacking to prevent the car from moving while on the jack.

Raise the rear wheel using a hydraulic jack on the right rear jacking point.

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.

H2. 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 towards the rear of the car until the retaining lug in the middle of the clip is exposed, then pull the clip towards you.

H3. Remove Guide Pins
Pry off the two plastic caps covering the guide pins. See IMAGE #47.

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

H4. Compress Piston back into Caliper
The piston must be fully pushed back into the caliper to make room necessary for the thicker replacement pads and to clear any wear lip on the rotor edge if it exists.

Place an 8" C-clamp as illustrated in IMAGE #49. 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.

H5. Disconnect Brake Pad Wear Sensor (Front Left and Rear Right wheels only)
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 order replacement 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 where it is plugged in. Open cover of housing and unplug old sensor and replace with the 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.

H6. 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 H4 to ensure the piston is compressed.

H7. 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. See IMAGE #20.

H8. 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.

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.

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. Binding calipers is 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.

H9. 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 H10.

OPTIONAL: measure rotor runout
See Step G9 for measuring runout.

H10. 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. Note that rear rotors contain brake shoes used for the parking brake. They can be a little more difficult to remove due to the shoes. Disengage the parking brake if removing the rear rotors.

See Step G10 for rotor replacement details.

H11. Prep Brake pads for installation
OPTIONAL: See Step G11 for brake pad prep details.

H12. Apply Anti-Squeal Compound to Caliper and Carrier
Apply a thin coat of anti-squeal compound to the piston surface being careful not to get any on the rubber seal which can cause swelling.

Apply a thin coat of anti-squeal compound to where the back of the outside pad comes in contact with the caliper (directly across from the piston face) and to the caliper where the outer pads ears will make contact.

Apply a thin coat of anti-squeal compound to the caliper carrier at the pad contact points. See IMAGE #58.

H13. Install brake pads and caliper
Push the inner pad, the one with 3 fingers on the back of the pad, into the piston. Place the outer pad onto the other side of the caliper. Note there are no fingers on the outer pad, unlike the front outer pads.

With the new pads installed, push the caliper back onto the caliper carrier.

H14. Install Guide Pins and caps
Torque to 30Nm (22 lb-ft). Do not over tighten the guide pins and ensure they are clean before installing. Install the 2 plastic cover caps.

H15. Install brake pad wear sensor
The new sensor should have been plugged into the enclosure in Step H5. Take the green sensor end and plug it into the notch on the top of the inner brake pad. It may take some wiggling and force to get it to snap in fully.

H16. Install spring retaining clip
Position the two outer ends of the clip first then push firmly towards the back of the car on the middle of the clip to engage the two hooked lugs. You can use the prybar to help push back the clip before inserting the hooks. Once in place you can tap the clip with a rubber mallet to ensure it is fully seated.

H17. Apply Anti-seize to Hub if necessary
If you do not see silver or copper anti-seize paste on the center hub, apply a thin coating now before installing the wheel. See IMAGE #44.

H18. Install rear wheel
Place the wheel on the hub and align the bolt holes. Reinstall the wheel bolts and hand tighten. Drop the car then torque each bolt to 120 Nm (93 lb-ft) in a star pattern. Failing to use a cross/star pattern can warp the wheel.

H19. Left rear Brake Pad
Repeat Steps H1 through H18 for the rear left wheel. There is no brake pad sensor to replace on the left rear wheel.
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 11:06 AM. Reason: formatting