How to replace a car combination valve

The combination valve balances your braking system. If it is broken, it should be replaced to ensure safe driving.

The combination valve contains everything you need to balance your brake system in one compact unit. Combination valves include metering valve, proportional valve and differential pressure switch. This valve kicks in every time you use the brakes and does a lot of work, meaning it can wear out at some point in your car's life.

If the combination valve is faulty, you will notice that the car will nose dive and come to a slow stop when braking hard. This is because the valve no longer measures the amount of brake fluid going to the front and rear wheels. If the valve is clogged, the brakes can fail altogether if there is no bypass in the system.

Necessary materials

• Hex key set
• socket wrenches
• Chemical resistant gloves
• reptile
• Drip tray
• flashlight
• Flat head screwdriver
• Jack
• Jack stands
• Large bottle of brake fluid
• Metric and Standard Linear Wrench
• Protective clothing
• Ratchet with metric and standard sockets
• Safety glasses
• Scan Tool
• Torque bit set
• Wrench
• Vampire pump
• Wheel chocks

Part 1 of 4: Car preparation

Step 1: Park your vehicle on a level, firm surface.. Make sure the transmission is in park (for automatic transmission) or 1st gear (for manual transmission).

Step 2: Install wheel chocks around the rear wheels, which will remain on the ground.. In this case, the wheel chocks will be located around the front wheels, since the rear of the car will be raised. Engage the parking brake to keep the rear wheels from moving.

Step 3: Raise the car. Using a jack recommended for the weight of the vehicle, raise it under the vehicle at the indicated jack points until the wheels are completely off the ground.

Step 4: Install Jacks. The jack stands should be located under the jacking points. Then lower the car onto the jacks. For most modern cars, the jack stand attachment points are on a weld right under the doors along the bottom of the car.

• AttentionA: It is best to consult the vehicle owner's manual for the correct jack installation location.

Part 2 of 4: Removing the Combination Valve

Step 1: Access the Master Cylinder. Open the car hood. Remove the cover from the master cylinder.

• A warning: Wear chemical resistant goggles before attempting to remove any part of the brake system. It is best to have goggles that cover the front and side of the eyes.

Step 2: Remove brake fluid. Use a vacuum pump to remove the brake fluid from the master cylinder. This will help prevent brake fluid from leaking out of the master cylinder when the system is open.

Step 3: Find a Combination Valve. Use your creeper to get under the vehicle. Look for a combination valve. Place a drip tray directly under the valve. Put on chemical resistant gloves.

Step 4: Disconnect the lines from the valve. Using adjustable wrenches, remove the inlet and outlet piping from the combination valve. Be careful not to cut the lines, as this can lead to serious brake repairs.

Step 5: Remove the valve. Remove the mounting bolts holding the combination valve in place. Lower the valve into the sump.

Part 3 of 4: Installing a New Combination Valve

Step 1: Replace Combination Valve. Install it in the place where the old valve was removed from. Install the mounting bolts with blue loctite. Use a torque wrench and tighten them to 30 in-lbs.

Step 2: Reconnect the lines to the valve. Screw the lines to the inlet and outlet ports on the valve. Use the line wrench to tighten the ends of the line. Don't overtighten them.

• A warning: Do not cross the hydraulic line when installing it. Brake fluid will leak out. Do not bend the hydraulic line as it may crack or break.

Step 3: With the help of an assistant, bleed the rear brake system.. Have an assistant depress the brake pedal. While the brake pedal is depressed, loosen the bleed screws on the left and right rear wheels. Then tighten them.

You will need to bleed the rear brakes at least five to six times to remove air from the rear brakes.

Step 4: With a helper, bleed the front brake system.. As your assistant depresses the brake pedal, loosen the front wheel bleed screws one at a time. You will need to bleed the rear brakes at least five to six times to remove air from the front brakes.

• Attention: If your vehicle has a brake controller, make sure you bleed the brake controller to remove any air that may have entered the duct.

Step 5: Bleed the Master Cylinder. Have your assistant depress the brake pedal. Loosen the lines leading to the master cylinder to let the air out.

Step 6: Prime the Master Cylinder. Fill the master cylinder with brake fluid. Install the cover back on the master cylinder. Depress the brake pedal until the pedal becomes firm.

• A warning: Do not allow brake fluid to come into contact with the paint. This will cause the paint to peel and flake off.

Step 7: Check the entire brake system for leaks. Make sure all air bleed screws are tight.

Part 4 of 4: Reset and check the brake system

Step 1: Restart the car's computer.. Locate your computer's digital data read port. Get a portable engine light tester and set ABS or brake parameters. Scan current codes. When codes are present, clear them and the ABS light should turn off.

Step 2: Drive the car around the block. Use a normal stop to make sure the braking system is working properly.

Step 3: Get the car out onto the road or into a car-free parking lot.. Drive your car fast and apply the brakes quickly and sharply. During this stop, the combination valve should operate correctly. The brakes may squeak a little under hard braking, but should not lock up the rear brakes. The front brakes should respond quickly. If the vehicle has an ABS module, the plungers can pulse the front brakes to prevent the front rotors from locking up.

• Attention: Watch the instrument panel while checking to see if the ABS light comes on.

If you're having trouble replacing a combination valve, consider seeking help from one of AvtoTachki's certified mechanics, who can perform service anytime, anywhere you choose.