Replacing the wheel cylinders in a BMW with drum brakes involves several key steps. Begin by gathering necessary tools, including brake line wrenches, metric socket wrenches, a torque wrench, and a brake bleeder kit. Prepare the vehicle on a stable surface, secure with wheel chocks, and elevate using a jack and stands. Safely remove the brake drum, then detach the old cylinder from the brake fluid line. Install the new cylinder, ensuring it matches the previous specifications, and reattach the brake line. Carefully reassemble the components and test for leaks and functionality to ensure optimal braking performance. Discover more about each step in greater detail.
Gather Necessary Tools
Before you start changing wheel cylinders in BMW drum brakes, gather the right tools. This makes the job smoother.
Start with a good set of brake line wrenches. They help you grip brake line fittings securely. You'll also need metric socket wrenches to take off the wheel and drum assembly. A torque wrench is needed to tighten bolts to the right specifications during reassembly.
A brake bleeder kit is useful to remove any air from the hydraulic system after you replace the cylinder. Use high-temperature brake grease to lubricate moving parts, which helps prevent squeaking. A brake cleaning spray will help clean debris from the drum and nearby parts before you put everything back together.
Use a sturdy jack and jack stands to safely lift the car and keep it steady while you work. Make sure your workspace is organized and well-lit to see clearly and work efficiently.
Prepare the Vehicle
To get your BMW ready for changing the wheel cylinder, follow these steps:
- Find a Safe Spot: Park your car on a flat and stable surface. Make sure there's enough room around the car so you can move easily. A level driveway or garage floor is perfect for keeping the car steady.
- Secure the Car: Put on the parking brake to stop the car from moving. Place wheel chocks behind the rear wheels to prevent any rolling.
- Loosen the Lug Nuts: Slightly loosen the lug nuts on the wheel with the drum brake. Don't take them off just yet.
- Lift the Car: Use a jack to lift the car to a height where you can comfortably reach the wheel and brakes. Put jack stands under strong parts of the car's frame to keep it stable.
- Check Everything: Double-check that the wheel chocks and jack stands are firm and in the right place. Look over everything to make sure it's all set up correctly.
Remove the Brake Drum
To take off the brake drum, first make sure the car is parked safely. Begin by removing the wheel. Loosen the lug nuts with a wrench. Lift the car with a jack, then take off the lug nuts completely to remove the wheel. Ensure the car is steady on jack stands before you go on.
With the wheel off, you can see the brake drum. Look for any screws or clips that might be holding it. Some BMW models have a screw or clip to keep the drum from moving during transport. If you find any, use a screwdriver to remove them.
If the drum is stuck due to rust or dirt, gently tap it with a rubber mallet to loosen it. Be careful not to hit too hard to avoid damaging the drum or other parts.
Here's a quick reference for the tools you'll need:
| Tool | Use | Note |
|---|---|---|
| Wrench | Loosen and remove lug nuts | Don't over-tighten |
| Screwdriver | Remove screws or clips | Use the right size |
| Rubber Mallet | Loosen stuck drums | Tap gently |
Once the drum is loose, slide it off the hub carefully.
Detach the Old Cylinder
To remove the old wheel cylinder, first find it at the top of the brake backing plate. This part helps the brakes work by pushing the brake shoes against the drum.
Start by carefully disconnecting the brake fluid line. Use a flare nut wrench so you don't damage the nut, as brake lines can be fragile.
Next, take off the bolts holding the wheel cylinder in place. Usually, there are two bolts. Use the right size socket wrench to take them out. Be careful not to harm the brake shoes or other parts while doing this.
If the cylinder is stuck, use a bit of penetrating oil to help loosen it.
Check the area around the cylinder for any wear and tear, like worn-out brake shoe linings or rusty parts.
Make sure to get rid of the old cylinder properly.
Install the New Cylinder
With the old cylinder out, it's time to put in the new one. Make sure the new cylinder matches the old one in size and type.
Put the new cylinder onto the brake backing plate and line it up with the holes. Use the right bolts and tighten them following the manufacturer's guidelines. This keeps the cylinder secure without causing damage.
Next, attach the brake line to the new cylinder. Line up the brake line fitting with the cylinder port before tightening to avoid cross-threading. Proper connections are key to avoiding fluid leaks, which can affect braking.
Check the rubber dust boots on the cylinder for any damage. These boots keep dirt and grime out, so they should be in good shape.
Once everything is connected, bleed the brake system to get rid of any air. Air in the system can make the brakes feel soft.
Make sure each step is done carefully so the new wheel cylinder works well with the brakes.
Reassemble and Test
Start putting the brake shoes back. Make sure they fit well on the backing plate. Check that each shoe lines up with the wheel cylinder pistons. Attach them with the return springs. Be careful so the brakes work right later. After the shoes are set, put the drum over them. Check that it turns smoothly.
Next, adjust the brake shoes using the star wheel adjuster. Turn it until the shoes just touch the drum. This makes sure the brakes work well. Once adjusted, put the wheel back on and lower the car.
Now, test the brakes. Look for any fluid leaks around the wheel cylinder. Press the brake pedal several times to build up pressure. Try stopping the car slowly a few times to see if the brakes work evenly.
| Step | What to Do |
|---|---|
| Fit Brake Shoes | Align with pistons, attach springs |
| Put on Drum | Ensure it turns freely |
| Adjust Shoes | Use star wheel for light contact |
| Check Brakes | Look for leaks, test pressure and stops |
People Also Ask
What Are the Signs of a Failing Wheel Cylinder in a BMW With Drum Brakes?
If a wheel cylinder in a BMW with drum brakes is failing, you might notice the car doesn't stop as well, see brake fluid leaking by the wheels, have brakes that wear unevenly, or feel a soft brake pedal. It's important to check it soon for safety.
How Often Should Wheel Cylinders Be Inspected or Replaced on a BMW?
Check the wheel cylinders on a BMW with drum brakes every 20,000 to 30,000 miles during regular brake maintenance. If you see leaks, rust, or brakes not working well, it's time to replace them.
Can I Use Aftermarket Wheel Cylinders for My BMW, or Should I Stick to OEM Parts?
You can use aftermarket wheel cylinders for your BMW, but it's usually best to stick with OEM parts. OEM parts fit perfectly and work well with your car. If you choose aftermarket, make sure they are good quality and meet the right standards.
Are There Any Special Precautions to Take When Working With Brake Fluid During Replacement?
Wear gloves and goggles when working with brake fluid because it can harm your skin and eyes. If you spill any, clean it up right away and throw it away safely. Follow the rules for getting rid of it properly to protect the environment.
What Are the Potential Consequences of Not Replacing a Faulty Wheel Cylinder Promptly?
If you don't fix a broken wheel cylinder quickly, your car might not stop as well. This means it takes longer to stop, which can be dangerous. It might also leak brake fluid, making it even harder to stop and causing accidents.