Nissan Almera is equipped with two independent braking systems: working and parking
The first, equipped with a hydraulic drive with a vacuum booster, provides braking when the car is moving, the second slows down the car in the parking lot.
Dual-circuit working system with a diagonal connection of the brake mechanisms of the front and rear wheels.
One hydraulic circuit provides the right front and left rear brakes, the other - the left front and right rear.
Elements of the brake system of a 4x2 car: 1 - floating caliper; 2 - front wheel brake hose; 3 - front wheel brake disc; 4 - front wheel brake tube; 5 - hydraulic drive reservoir; 6 - ABS block; 7 - vacuum amplifier; 8 - pedal assembly, 9 - brake pedal; 10 - rear parking brake cable; 11 - rear wheel brake tube; 12 - brake mechanism of the rear wheel; 13 - rear wheel brake drum; 14 - parking brake lever; 15 - sensor for signaling an insufficient level of working fluid; 16 - brake master cylinder
If one of the circuits of the service brake system fails, the second circuit is used to stop the car with sufficient efficiency.
Brake pedal - suspension type. A brake light switch is installed in the bracket of the pedal assembly above the brake pedal - its contacts close when the pedal is pressed.
To reduce the effort on the brake pedal, a vacuum booster is used, using the vacuum in the receiver of a running engine.
The vacuum booster is located in the engine compartment between the pedal pusher and the main brake cylinder and is attached with four nuts (through the bulkhead) to the pedal bracket.
The vacuum amplifier is non-separable, it is replaced in case of failure.
The main brake cylinder is fastened with nuts to two studs of the vacuum booster housing.
On top of the cylinder there is a reservoir of the hydraulic drive of the brake system, in which there is a supply of working fluid.
The tank body is marked with maximum and minimum liquid levels, and a sensor is installed in the upper part, which, when the liquid level drops below the MIN mark, turns on the signaling device in the instrument cluster.
When the brake pedal is pressed, the pistons of the master cylinder move, creating pressure in the hydraulic drive, which is supplied through pipes and hoses to the working cylinders of the wheel brakes.
1 - brake hose; 2 - fitting for bleeding hydraulic brakes; 3 - a bolt of fastening of a bracket to a directing finger; 4 - guide pin; 5 - protective cover of the guide pin; 6 - guide pads; 7 - support; 8 - brake pads; 9 - brake disc
The brake mechanism of the front wheel is disc, with a floating caliper, which includes a caliper, made together with a single-piston wheel cylinder.
1 - bolt securing the bracket to the guide pin; 2 - support; 3 - guide pin; 4 - protective cover of the guide pin; 5 - brake disc; 6 - brake pads; 7 - spring clips of pads; 8 - shoe guide
The brake shoe guide is attached to the steering knuckle with two bolts, and the bracket is attached with two bolts to the guide pins installed in the holes of the shoe guide.
Protective rubber covers are installed on the fingers.
Grease is placed in the holes for the pins of the shoe guide.
When braking, the fluid pressure in the hydraulic drive of the brake mechanism increases and the piston, moving out of the wheel cylinder, presses the inner brake pad against the disc.
Then the bracket (by moving the guide pins into the holeyah guide pads) moves relative to the disc, pressing the outer brake pad against it.
A piston with a rectangular rubber sealing ring is installed in the cylinder body.
Due to the elasticity of this ring, a constant optimal gap is maintained between the disc and the brake pads.
The brake mechanism of the rear wheel with the drum of the car 4x2 removed: 1 - brake shield; 2 - rear brake shoe with parking brake lever; 3 - clamping spring pads; 4 - spring cup; 5 - support post; 6 - upper coupling spring; 7 - wheel cylinder; 8 - spacer bar with clearance adjuster; 9 - regulator spring; 10 - front block; 11 - parking brake cable; 12 - lower return spring
The brake mechanism of the rear wheel is drum, with a two-piston wheel cylinder and two brake shoes, with automatic adjustment of the gap between the shoes and the drum.
The brake drum is also the hub of the rear wheel and the bearing is pressed into it.
Elements of the mechanism for automatic adjustment of the gap between the pads and the drum of a 4x4 car: 1 - twisted spring of the threaded tip; 2 - threaded tip of the spacer bar; 3 - spring regulator lever; 4 - spacer bar; 5 - twisted spring of the spacer bar; 6 - leaf spring; 7 - ratchet nut
The mechanism for automatic adjustment of the gap between the shoes and the drum consists of a composite spacer bar for the shoes, the regulator lever and its spring.
It starts working when the gap between the pads and the brake drum increases.
Elements of the brake mechanism of the rear wheel of the car: 1 - spring cup; 2 clamping spring pads; 3 - support post; 4 - front block; 5 - upper coupling spring; 6 - wheel cylinder; 7 - spacer bar; 8 - regulator spring; 9 - rear shoe with parking brake lever; 10 - parking brake cable spring; 11 - lower return spring
When the brake pedal is pressed, under the action of the pistons of the wheel cylinder, the pads begin to diverge and press against the drum, while the protrusion of the regulator lever moves along the cavity between the teeth of the ratchet nut.
At a certain amount of pad wear and the brake pedal is depressed, the adjuster lever has enough travel to turn the ratchet nut one tooth, thereby increasing the length of the spacer bar and at the same time reducing the gap between the pads and the drum.
In this way, the gradual lengthening of the spacer bar automatically maintains the clearance between the brake drum and the shoes.
The wheel cylinders of the brake mechanisms of the rear wheels are the same.
The front pads of the brake mechanisms of the rear wheels are the same, while the rear ones are different - they are mirror-symmetrically equipped with non-removable parking brake levers.
The spacer bar and ratchet nut of the left and right wheel brakes are different.
The ratchet nut and lug of the left wheel spacer bar are left hand threaded, while the ratchet nut and lug of the right wheel spacer bar are right hand threads.
The levers of the brake mechanisms of the left and right wheels are mirror-symmetrical.
The car is equipped with an anti-lock braking system (ABS), which provides more efficient braking by reducing the fluid pressure in the brake mechanisms of the wheels at the time of their blocking.
The fluid from the master brake cylinder enters the ABS unit, and from there it is supplied to the brake mechanisms of all wheels.
ABS unit: 1 - control unit; 2 - hole for connecting the tube of the brake mechanism of the front right wheel; 3 - hole for connecting the tube of the brake mechanism of the rear left wheel; 4 - hole for connecting the tube of the brake mechanism of the rear right wheel; 5 - hole for connecting the brake pipe mechanism of the front left wheel; 6 - hole for connecting the tube of the main brake cylinder; 7 - pump; 8 - hydraulic block
The ABS unit, mounted in the engine compartment on the right side member, near the bulkhead, consists of a hydraulic unit, a modulator, a pump and a control unit.
ABS operates depending on the signals from the wheel speed sensors. The sensors are inductive type.
The front wheel speed sensor is located in the wheel hub assembly - it is inserted into the groove of a special sensor mounting ring sandwiched between the end surface of the outer ring of the hub bearing and the shoulder of the steering knuckle hole for the bearing.
The drive disk of the front wheel speed sensor is a protective washer of the hub bearing, located on one of the two end surfaces of the bearing.
This dark colored washer is made of magnetic material. On the other end surface of the bearing there is an ordinary light-colored protective washer made of thin sheet metal.
When the vehicle is braked, the ABS control unit detects the start of wheel lockup and opens the corresponding modulator solenoid valve to release the pressure of the working fluid in the channel.
The valve opens and closes several times per second, so you can verify that the ABS is working by the slight vibration of the brake pedal at the time of braking.
Parking brake drive - manual, mechanical, cable, on the rear wheels.
It consists of a lever, a front cable with an adjusting nut on its tip, an equalizer, two rear cables and levers in the rear wheel brakes.
The parking brake lever, fixed between the front seats on the floor tunnel, is connected to the front cable.
An equalizer is attached to the rear end of the front cable, into the holes of which the front ends of the rear cables are inserted.
The rear cable ends are connected to the parking brake levers attached to the rear shoes.
During operation (until the rear brake pads are completely worn out), adjustment of the parking brake drive is not required, because. extension of the brake spacer compensates for pad wear.
The parking brake actuator only needs to be adjusted if the cables or the parking brake lever have been replaced.
Possible malfunctions of the brake system and methods of correction
Cause of malfunction Remedy
Increased brake pedal stroke
Leakage of brake fluid from working brake cylinders - Replace failed working brake cylinders, wash and dry pads, discs and drums
Air in the brake system - Remove air by bleeding the system.
Rubber o-rings in brake master cylinder damaged - Replace master cylinder
Damaged rubber brake hoses - Replace the hoses and bleed the system.
Increased runout of the brake disc (more than 0.03 mm) - Grind or replace the disc if the thickness of the braked discs of the front of the wheels is less than 19.8 mm
Insufficient braking performance
Oiling the brake pads - Wash and dry the pads
Jamming of pistons in working cylinders - Eliminate the causes of jamming, replace damaged parts
Complete wear of linings brake pads - Replace brake pads
Brake overheating - Stop immediately and let the brakes cool down
Use of poor quality pads - Use original pads or products from companies specializing in the production of brake parts
Violation of the tightness of one of the circuits (accompanied by the failure of the brake pedal) - Replace damaged parts, bleed the system
Brake pedal misalignment - Determine the cause of the increase in full travel and replace the damaged parts
Violation of the adjustment of the protrusion of the rod of the vacuum brake booster - Contact the service to adjust the booster
Anti-Lock Braking System (ABS) Malfunction - Contact a Service Center to Check Your Anti-Lock Braking System
Incomplete release of all wheels
No free play on the brake pedal
Increased protrusion of the vacuum brake booster rod - Replace the brake master cylinder
Contact the service to adjust the amplifier
Swelling of the rubber seals of the main cylinder due to the ingress of gasoline, mineral oils, etc. into the liquid. - Flush and bleed the entire hydraulic drive system, replace rubber parts
Jammed master cylinder pistons - Check and replace master cylinder if necessary
Braking one wheel when the pedal is released
Broken or loose parking brake shoe return springs - Replace spring
Piston sticking in the working cylinder due to contamination or corrosion of the body - Replace the working cylinder and bleed the hydraulic brake system
Swelling of the sealing rings of the working cylinder due to the ingress of foreign impurities into the liquid - Replace the working cylinder and bleed the hydraulic brakes
Violation of the position of the caliper relative to the brake disc when the mounting bolts are loosened - Tighten the mounting bolts, if necessary, replace the damaged parts
Incorrect parking brake adjustment - Adjust the parking brake
Anti-Lock Braking System Abnormality - Have an Anti-Lock Braking System Test
Sliding or pulling the car to the side when braking
Jamming of the piston of the working cylinder - Check and eliminate the jamming of the piston in the cylinder
Clogging of any tube due to dent or blockage - Replace or clean tube
Dirty or oily discs, drums and brake pads - Clean brake parts
Wheels out of alignment - Adjust wheel alignment
Various tire pressure - Set the required tire pressure
One of the brake circuits does not work (accompanied by a decrease in braking efficiency) - Replace damaged parts and bleed the system.
If this does not lead to the desired result, contact the service to check the anti-lock brake system (if installed on the car)
Increased effort on the brake pedal when braking
Vacuum booster defective - Replace booster
The hose connecting the vacuum booster and the engine intake pipe is damaged or its fastening is loose - Replace the hose
Swelling of rubber cylinder seals due to the ingress of gasoline, mineral oils, etc. into the liquid. - Replace cylinders, flush and bleed the system
Squeak or vibration of the brakes
Oiling the friction linings - Clean the linings with a wire brush using warm water and detergent.
Remove the causes of fluid or grease getting on the brake pads
Worn pads or foreign matter in them - Replace the pads
Excessive runout or uneven wear (felt by vibration of the brake pedal) of the brake disc - Grind or replace the disc if the thickness of the brake discs of the front wheels is less than 19.8 mm