When the brake light is on, the brakes are less responsive, or the brake pedal begins to sink to the floor, it's possible that the brake fluid has leaked. Another common symptom is new puddles under the car; in this case, the liquid is colorless and not as viscous as other engine oils so the consistency is similar to cooking oil.
Step
Method 1 of 6: Finding Leaks
The first step to repairing brake fluid is to diagnose the location and severity of the leak. Then, you need to make repairs.
Step 1. Open the hood and check the brake fluid reservoir
This reservoir is on the driver's side towards the rear of the engine compartment. If the brake fluid is low, there may be a leak.
Step 2. Check for leaks by checking for oil puddles under the car
The location of the inundation also helps determine the general location of the leak.
Step 3. Spread the newspaper on the floor under the car, where the leak is supposed to occur
Step 4. Pump the brake pedal to force the oil out through the leaking section
Make sure the car is NOT starting when you do this. Starting the car will make the brake fluid splatter quickly and the leak is difficult to control, depending on the severity.
Step 5. Crawl under the car and look for the spot where the oil drips from the brakes
If the leak is coming from inside the wheel, you may need to remove the wheel to check for leaks in the hoses and calipers.
If your car has brake drums, it's possible that the wheel cylinder is leaking. You will need to remove the wheel drum to check it
Step 6. Check for leaks in the master cylinder
The location of the master cylinder varies from vehicle to vehicle so we recommend reading the user manual to find it. If you don't have it, look it up on the internet.
Step 7. Make sure the master cylinder cover is tightly closed
Occasionally, liquid may seep from a cover that is not securely fastened.
Method 2 of 6: Rebuilding the Brake Calipers
Not many mechanics rebuild calipers, wheel cylinders, or main cylinders completely from scratch. Instead, they ship the components to a central rebuild station and reassemble the newly rebuilt components. Buying new calipers is almost always better than rebuilding them. The price of calipers has dropped, and is only slightly more expensive than rebuilt calipers. However, if you want to take on a challenge, buy a rebuild kit at a repair shop to rebuild the brake calipers.
Step 1. Remove the old calipers
- Purchase a caliper rebuild kit from a repair shop or dealer.
- Remove the brake bleeder bolt using a flare-nut wrench. If necessary, tap gently and apply penetrating oil to loosen the bolts without breaking them.
- Remove the steel and brake lines using a flare-nut wrench. Replace this hose if it is cracked or worn before putting the calipers back on the car.
- Remove bearings, shims (a kind of flat ring to fill gaps between objects), springs, and sliders or caliper pins.
- Remove the outer dust seal.
- Place a piece of wood slightly thicker than the two brake pads stacked together in the caliper behind the piston.
- Blow low pressure compressed air into the inlet port. This step will bring up the piston.
Step 2. Replace the pistons
- Lubricate the new pistons available in the rebuild kit using brake fluid.
- Insert the new piston into the caliper by pressing it sufficiently with your finger.
Step 3. Replace the calipers
- Replace the outer dust seal.
- Replace bearings, shims, springs, and sliders or caliper pins. Use the new parts available in the repair kit, and discard the old parts.
- Reconnect the steel and rubber conduit.
- Replace the brake drain bolt.
- Test the brakes to make sure they are no longer leaking.
Step 4. Remove all air from the brake system
Method 3 of 6: Replacing the Wheel Cylinder
Defective wheel cylinders can leak brake fluid. Replace the wheel cylinder with a completely new unit as it is easier and only slightly more expensive than rebuilding components.
Step 1. Remove the wheel
- Remove the hubcap (rim cover) and tires.
- Raise the car using a jack so the wheels don't touch the ground.
- Remove the lug nut and wheel.
- Spray the brake steel line fittings with penetrating oil to loosen any rust.
Step 2. Remove the brake drum
- Remove the rubber stopper behind the backing plate.
- Loosen the self-adjuster (star wheel) to lower the brake shoes. If you adjust the self-adjuster in the wrong direction, the drum will tighten and not rotate. Use a flat head screwdriver to remove the adjuster arm, if necessary.
- You may need to use a hammer to tap the center of the drum to loosen the rust surrounding the center piece.
- Remove the drums.
- Place the drip tray under the brake shoes. If the brake shoes are stained with fluid, you will also need to replace them.
- Spray the area with brake cleaner to remove dirt and fluid.
Step 3. Loosen the brake steel line
- Prepare a vacuum hose to prevent brake fluid from leaking from the brake steel line. Install a screw or bolt at one end of the hose.
- Locate the brake steel channel in the plate where it is screwed into the wheel cylinder and use a wrench to loosen the brake line fitting.
- Remove the fitting.
- Attach a vacuum hose to the line to prevent leakage.
Step 4. Replace the wheel cylinder
- Locate the two retaining bolts on the backing plate that secure the wheel cylinder.
- Use a socket wrench to loosen the bolt
- Remove the old wheel cylinder.
- Insert the brake steel line fitting into the new cylinder. Screw as far as possible by hand.
- Insert the bolt back into the backing plate and screw it to secure the new cylinder.
Step 5. Remove all air from the brake system
Read the guide in Method 6.
Method 4 of 6: Replacing Brake Steel Lines and Hoses
If the brake hose is cracked and brittle or mushy and sticky, the hose needs to be replaced. If there are rusty spots on the brake lines, you will need to sand them gently to see if the metal is thinning. If the steel conduit has a thin section of the metal wall, it is best to replace it.
Step 1. Remove the tire that is above the leaking brake line
Step 2. Remove the brake line from the fitting closest to the master cylinder
Use the correct flare nut wrench.
Step 3. Remove all bracket clips that secure the brake line
Step 4. Disconnect the brake line from the brake caliper using a wrench
Step 5. Loosely install the new brake line on the caliper
The length of the new brake line must be the same as the old one.
Step 6. Replace the bracket clip with the new channel
Step 7. Install the brake line with the fitting closest to the master cylinder using a wrench
Step 8. Tighten all joints
Step 9. Remove all air from the brake system as described in Method 6
Method 5 of 6: Replacing the Master Cylinder
Most modern brake systems are divided into two circuits, with two wheels for each system. Should one circuit fail, the other system brakes will still function. The master cylinder applies pressure to both circuits. Usually the cost of replacing a master cylinder is cheaper than rebuilding it.
Step 1. Open the hood and locate the master cylinder
Step 2. Remove the brake fluid reservoir cover
Step 3. Suck brake fluid from the master cylinder using a turkey baster
After that, pour it into a plastic container.
Step 4. Disconnect all electrical connectors from the master cylinder
Step 5. Disconnect the brake line using a wrench by turning it counterclockwise
Step 6. Remove the master cylinder mounting bolt with a socket wrench
Step 7. Remove the old master cylinder
Step 8. Install the new master cylinder by tightening the mounting bolts
Step 9. Connect the brake line to the master cylinder using a wrench
Step 10. Connect the electrical connector with the new master cylinder
Step 11. Remove all air from the air system
Method 6 of 6: Bleed Air from the Brake System
After repairing the brake system, remove all air and brake fluid from the system and replace it with new brake fluid. You will need someone's help for this project.
Step 1. Ask the assistant to sit in the driver's seat
Step 2. Remove the brake fluid reservoir cover above the master cylinder
Step 3. Drain all the brake fluid from the master cylinder using a turkey baster
Store the used brake fluid in a plastic bottle. Wipe off deposits with a clean, lint-free cloth.
Step 4. Refill the brake fluid reservoir with a new one
Check the underside of the reservoir cover or the vehicle's user manual to find the right type of brake fluid for the car.
Step 5. Loosen the brake fluid drain screw located on the caliper or wheel cylinder on the right rear of the car
You will have to drain each brake at a time to keep the system from drawing air in. Start from the right rear of the car.
Step 6. Attach the vinyl hose to the drain screw
Step 7. Place the other end of the vinyl tube into a clear plastic bottle
Step 8. Ask an assistant to press the brake pedal to the lowest point of its normal range (you may need a block under the brake pedal to keep it from going past this point)
Step 9. Tighten the right front brake fluid drain screw after all the water bubbles have cleared
Step 10. Ask the assistant to pump the brake pedal until it becomes firm and builds up pressure
This step will draw the fluid into the master cylinder body. Oil should splash into the bottle every time the assistant pumps the brakes. Do this until the new brake fluid starts to come out.
Continue filling the master cylinder with brake fluid. The oil should not be half empty
Step 11. Ask the assistant to press the brake pedal again
Tighten the brake fluid drain screw and remove the hose.
Repeat the process until all four wheels have been drained. Again, you'll need to drain one brake at a time
Step 12. Fill the master cylinder with brake fluid
Step 13. Test the brakes to make sure they are working normally again
Tips
- You can use an open end wrench to remove the brake steel line. However, this type of wrench tends to damage steel easily so spray the area with lots of penetrating oil when you slowly release the brake line.
- If the brake pedal still feels soft after completing the repair, it means that you will need to re-drain the brake system to remove any air bubbles.
- If you are repairing a set of brakes, be sure to replace the same part on the opposite side of the axle. Always treat the brakes as a set of axles instead of fixing on individual wheels.
Warning
- Try not to damage the brake drain bolt while removing it.
- Depressing the brake pedal to its lowest point while draining the brakes can damage the seals on an aging or poorly maintained system. Therefore, try not to do it.
- Comply with all local regulations regarding brake fluid disposal.
- Follow the manufacturer's instructions for raising the car with a jack.
- Always wear protective clothing, goggles and gloves when handling brake fluid.
