DIY Auto Service; Hydraulic Brake System Diagnosis and Repair
Each component in the brake system with rubber seals needs to be replaced.In order to diagnose the hydraulic problem in the brake system, you must know what a good system feels like when you step on the brake pedal to brake.How far did the pedal move before it was firm?Is the pedal solid or does it feel like a sponge?Is the pedal going further than normal, and is the brake warning light on?Is the pedal stroke affected by the temperature of the brake fluid?Drum brakes may not be adjusted.
Disc brake pads may be pushed back too far from the rotor due to excessive wheel bearing end or rotor operationout.The fluid may be polluted by air.Remember that the air is compressed.Part of the hydraulic system is likely to leak or be filled with air.Look for fluid leakage on lines, valves, wheel cylinders or calipers.
The moisture in the brake system becomes hot enough to boil.Steam is a compressed gas.Flush brake system.Check if the brakes are not dragged.The brake line may be too close to the hot exhaust and the brake fluid is boiling.The boiling brake fluid is a gas that can be compressed.
This is especially true today for the catalytic converter exhaust system.Look for the missing heat shield or isolate the line from the heat.One of the main seals in the main cylinder leaks the liquid back into the tank while stepping on the brake pedal.
The main cylinder needs to be repaired or replaced.The pulsating is caused by uneven or twisted rotor surface or outside the round drum brake drum.The main cylinder may have a hydraulic failure due to a leak in the main cylinder itself or in the brake system.
Since the system is divided into two separate hydraulic systems, it will only affect half.If the main piston loses fluid, it does not make the hydraulic connection between it and the secondary piston when the piston moves forward.The short rod at the front of the main piston will mechanically push the auxiliary piston forward.
The pedal will go further than normal, but the secondary piston will still create pressure for a part of the hydraulic system.The spring will bring the main piston back to the starting point.If the secondary piston loses fluid, the movement of the brake will still create a hydraulic connection between the primary piston and the secondary piston.
The secondary piston will move forward and down on the rod at the front of the piston.The main piston can now generate pressure in the main part of the system.The spring at the front of the secondary piston returns the secondary piston to a stationary position.
The pumping master cylinder allows more fluid to enter the pumping part of the two pistons.This is achieved through the forward bending movement of the main seal.When the seal is bent, it allows the fluid from the vent to bypass the seal and fill the cavity in front of the piston.
Small holes drilled behind the main piston also allow fluid flow from the replenishment port.Air is not allowed to enter as long as there is fluid in the reservoir.If the reservoir is running very low, the air may be pumped into the hydraulic part and cause problems, such as the sponge pedal.
Most vehicles use master cylinders that can be replaced.Some vehicles use the main cylinder of ABS and can only be replaced as an assembly.Disconnect any electrical connectors from the main cylinder.
Loosen the line of the main cylinder using a suitable size tubing wrench.Loosen the mounting bolts at the back of the main cylinder.Remove the line and mounting bolts and remove the main cylinder.
Note: do not apply any brake fluid to the paint surface as this will erode the paint and plastic.The main cylinder should be deflated before installation.When using the bleeder adapter, which is usually installed in the box, fill the tank with a screwdriver and pump the piston slowly.
When pumping, pay attention to when the bubbles stop flowing out of the hose submerged in the brake fluid container.The main cylinder is a bench ready for installation.Install bolts and torque according to specifications.
Install the line loosely.
Let someone push the pedal down and tighten the line.Install electrical connectors.Fill the reservoir to the \"full\" mark.Step on the brake pedal and see how it feels.Note: depending on the problem, the rest of the brake system may not have to bleed at this time.
The layout of the hydraulic system will determine the order of bleeding.The most common method is to use the closest pattern.Start with the farthest bleeder screw and work towards bleeder closest to the main cylinder.
Note: anti-vehicleLock Brake System (ABS), special procedures may be required to discharge the system.Note that some systems use a fully charged accumulator that stores the hydraulic pressure that needs to be exhausted before opening the system.Confirm the service information.Popular on rear wheel drive cars, light and medium trucks.
This means that part of the main cylinder operates the front brake and the other part operates the rear brake.Since the main cylinder is located on the left side of the North American product engine compartment.The general rule is that the farthest brake drain is behind the right.
Fill the tank with the correct brake fluid.Use one of the three bleeding methods to open the right posterior bleeding screw.Turn this screw on and off until the clean air-free liquid comes out (no bubbles ).
Check the level as needed.
Move to the left rear vent screw and perform the same operation.Move to the front drain screw on the right side and perform the same operation.Move to the left front drain screw and perform the same operation.
Re-check the fluid in the reservoir and do not overfill it.Clean the area with brake fluid on it so as not to look like a leak.Do not apply any brake fluid on the paint surface.
Mainly used for front wheel drive cars.
Since their front brakes are about 90%, the front and rear brakes do not give the vehicle enough brakes if the front hydraulic system fails.To separate the brake system by 50/50, the right front brake is in the same hydraulic circuit as the left rear brake.The left front brake is in the same circuit as the right rear brake.
The connected wheels form an \"x\" shape in the car.There are usually 4 lines off the main cylinder.Fill the tank with the correct brake fluid.
Use one of the three bleeding methods to open the right posterior bleeding screw.Turn this screw on and off until the clean air-free liquid comes out.Check the level as needed.Move to the left front drain screw and perform the same operation.
Move to the left rear vent screw and perform the same operation.Move to the front drain screw on the right side and perform the same operation.Re-check the fluid in the reservoir and do not overfill it.
Clean the area with brake fluid on it so as not to look like a leak.Do not apply any brake fluid on the paint surface