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Replacing Your Brake Ducts
 

Pelican Technical Article:

Replacing Your Brake Ducts

Nick Czerula

Time:

2 hours2 hrs

Tab:

$100

Talent:

**

Tools:

Set of sockets, wrenches, screwdrivers

Applicable Models:

BMW 323i Sedan/Wagon (1999-00)
BMW 325i Sedan/Wagon (2001-05)
BMW 328i Sedan (1999-00)
BMW 330i Sedan (2001-05)

Parts Required:

Brake duct, splash shield

Hot Tip:

Put your fasteners in a Ziploc bag

Performance Gain:

Proper brake cooling.

Complementary Modification:

Change the brake pads if worn

The disc brakes on your BMW E46 are extremely efficient for slowing down and stopping the vehicle under most routine conditions. The friction of brake pads against the brake rotors (discs) heats up the brakes: The kinetic motion of the moving vehicle is converted to thermal energy. Slowing down from a high speed drive, controlling the speed of descent through a long downhill, repeated high speed stops, or an emergency braking situation all contribute to a great deal of brake heating. Hot brake rotors can warp, causing uneven braking. Brake pads that are heated beyond a certain point are less effective. And finally, enough heat in the brakes may boil the brake fluid; this causes major loss of braking power.

The brake rotors are designed to dissipate much of this heat as they spin through the air;  an additional and important source of brake rotor cooling air are the brake cooling ducts, located in the right and left corners of the front bumper. Each duct sends cooling air to the brake rotor, improving brake performance. If a duct is damaged, brake performance can suffer, especially under repetitive braking situations. Impact with a parking block, curb, or large speed bump can damage a brake duct and the lower splash shield. Repairs to a brake-cooling duct can be done by removing the front wheel and working in the wheel well. 

Remember that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If  you are working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability. 

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Start by loosening the wheel studs on the side of your vehicle that you are servicing. Do not remove them, just break the studs free. Raise the vehicle off the ground and support it safely using a jack stand. Remove the wheel studs and remove the wheel. See our Pelican Parts technical article on Jacking Up Your BMW for more information.

Working at the lower corner of the front bumper, remove the two splash shield screws (green arrows).
Figure 1

Working at the lower corner of the front bumper, remove the two splash shield screws (green arrows).

While, working inside the front wheel well, remove the three splash shield screws (green arrows).
Figure 2

While, working inside the front wheel well, remove the three splash shield screws (green arrows). NOTE: The driver's side wheel well is shown here but the passenger side is similar.

Pull the splash shield from the front bumper and disconnect the ambient air temperature sensor electrical connector (left side only).
Figure 3

Pull the splash shield from the front bumper and disconnect the ambient air temperature sensor electrical connector (left side only).

If you are replacing the splash shield, lever out the ambient air temperature sensor retaining tabs with a small flathead screwdriver and remove the sensor from the splash shield (left side only).
Figure 4

If you are replacing the splash shield, lever out the ambient air temperature sensor retaining tabs with a small flathead screwdriver and remove the sensor from the splash shield (left side only).

Working inside the front wheel well, remove the brake duct screws, then remove the brake duct from the vehicle.
Figure 5

Working inside the front wheel well, remove the brake duct screws, then remove the brake duct from the vehicle.

When installing the brake duct, be sure to properly align the opening in the brake duct with the alternator duct, then align that with the bumper vent and install screws to attach the duct to the vehicle (left side only).
Figure 6

When installing the brake duct, be sure to properly align the opening in the brake duct with the alternator duct, then align that with the bumper vent and install screws to attach the duct to the vehicle (left side only). It's a good idea to check the alternator cooling duct for debris at this point too. Leaves and other road debris can get trapped in the duct, preventing proper alternator cooling. This could lead to an overheated alternator and a charging system failure.

Comments and Suggestions:
douig Comments: Understood, but my question is the same. The brake duct on mine & other E46 M3 dead ends at the back of the inner fender liner. There appears to be optional openings covers that snap on/off in front of the brakes. Is there any reasonable way to use the existing brake ducts / openings?

Thanks,
Doug
November 26, 2017
  Followup from the Pelican Staff: I have seen people cut the fender liner open and add ducts, as far as available parts I am not sure. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Doug Comments: I have an E46 2002M3. The "brake ducts" direct the air flow to the back of the fender liner, not even close to what appears to be optional openings covers snap on/off in front of the brakes.

What am I missing?

Thanks,
Doug
November 17, 2017
  Followup from the Pelican Staff: This article not for M3 models. Yours will be different. We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

Give our parts specialists a call at 1-888-280-7799. Give them the year and model of your vehicle and ask them to email you the relevant pages from the parts book.

- Nick at Pelican Parts
 

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Page last updated: Mon 1/15/2018 02:30:57 AM