Diagnostics of brake system faults (Nissan Patrol Y60)

The brake pedal is too hard to press

Brake pads installed (disc brakes), or friction linings of shoes (drum brakes) not that type. Check, replace.

The patency of the brake line coming from the master brake cylinder (MBC) is impaired. Check the lines, eliminate the cause of the blockage, or replace them.

The brake pedal axle is jammed. Perform necessary repairs or replace axle bolt and bushings.

Wheel cylinder/caliper piston is stuck. Perform a major overhaul of the cylinder/caliper.

The brake booster is not functioning properly. Check the amplifier for proper operation (see Chapter Brake system).

There is a "grabbing" of the brakes

The patency of the master cylinder fittings is impaired. Check and clean the brake master cylinder and brake fluid reservoir.

Wheel cylinder/caliper piston is stuck. Make any necessary repairs.

The parking brake cable is jammed. Replace the cable.

The tension springs of the drum brake shoes are broken or stretched out. Replace defective springs.

The adjustment of the vacuum booster/master cylinder tappets is disturbed. Check and make any necessary adjustments.

Note: To detect signs of brake seizure, jack up the vehicle and support it. Rotate the wheels by hand one by one to check for seizure. If all wheels rotate freely, have an assistant press and release the foot brake pedal. Make sure that the brakes release the wheels without delay. A blocked brake master cylinder nipple causes simultaneous seizure of two wheels whose brakes are included in the corresponding specific hydraulic circuit. Release the bleeder valve on one of the seized wheels, making sure that the seizure is caused by an increase in pressure in the circuit.

A jammed parking brake drive cable usually leads to the rear driveshaft seizing. To check, jack up the rear of the car and place it on supports, disconnect the drive cable from the actuator lever - the rear driveshaft should start to rotate freely.

There are noises emitted by the brake mechanisms

Braking is accompanied by a squealing sound. The friction lining material is polished. Remove the suspected pads/shoes (see accompanying illustration) and remove the polish from their surface using sandpaper.



Braking is accompanied by a grinding noise. The friction lining material is worn out. Check the condition of the pads/shoes and discs/drums of the suspected brake mechanisms. Replace worn pads/shoes, have the damaged disc/drum reground (see accompanying illustration).

Note: Brake squeal is most often caused by polishing the brake pad friction surfaces to a shine, but other possible causes such as using the wrong type of pads or missing anti-squeal springs or anti-squeal pads should not be overlooked.

If the friction linings of the pads/shoes have worn down to the base metal, all four pads/shoes must be replaced, even if they are in good condition on the opposite wheel.

If the brake disc/drum is heavily scratched, it should be ground or replaced to restore braking efficiency.

There is a low "softness" of the brake pedal stroke

The automatic brake regulator for the rear wheels has failed. Make the necessary repairs or replace the regulator.



The brake fluid level has dropped. Check the system for signs of leaks - carefully inspect all fittings (see accompanying illustration). Perform necessary repairs, restore fluid levels and bleed the hydraulic system.

Air has entered the hydraulic system. Bleed the system.

Note: In most cases, the "softness" of the brake pedal is due to air entering the hydraulic system. It is imperative to find the source of air penetration and eliminate the defect (seals or nipple connections). Then the system should be bled.

Defective brake system components are easy to identify by the presence of traces of brake fluid leaks on their surface. Wheels lock when braking

The friction linings of the brake pads/shoes become clogged due to oil or brake fluid getting on them. Identify and eliminate the cause of contamination, replace pads/shoes.

The brake drum is deformed. Check and make any necessary replacements.

The wrong type of brake pads/shoe linings are installed. Check, replace.

The brake shoe tension springs are broken or stretched. Check and replace defective springs.

The pressure regulating valve is faulty. Replace the valve.

Note: Remove all wheels and inspect the friction linings for wear and signs of oil contamination. Check the condition of the brake shoe tension springs by comparing their free length with that of new springs.

A sign of brake drum deformation is pulsation of the brake pedal during light braking.

If the rear wheels are constantly locked, you should check the serviceability of the pressure regulator.

There is pedal pulsation during braking

The brake drum/disc is deformed. Turn the defective component.

The front or rear wheel hub bearings are worn out, or their preload is loose. Adjust the preload or replace the defective bearings.

Note: Warped brake drums/discs must be resurfaced. This work should be entrusted to specialists at a car service workshop, who will also help you determine whether this procedure is appropriate. You may have to purchase new components.

Brake fade occurs

The friction linings of the brake pads/shoes have become clogged due to oil or brake fluid getting on them. Identify and eliminate the cause of contamination, replace pads/shoes.



The brake drum is deformed. Check and make any necessary replacements.

The automatic rear brake adjuster has failed. Perform any necessary repairs to the regulator.

The wrong type of brake pads/shoes are installed. Make a replacement.

The brake fluid is contaminated. Bleed the hydraulic system and fill it with fresh brake fluid. Bleed the brakes.

Note: In most cases, brake fade occurs as a result of sudden and frequent braking, which leads to heating of the friction linings and discs/drums of the brake mechanisms. After the mechanisms cool down, braking should return to normal.

The brake mechanisms are overheating

The automatic brake regulator of the rear wheel has failed. Make any necessary repairs.

The brake shoe tension springs are broken or stretched. Check and replace defective springs.

The adjustment of the vacuum booster/master cylinder tappets is disturbed. Check and make any necessary adjustments.

Wheel cylinder/caliper piston is stuck. Make any necessary repairs.



Damaged or blocked hydraulic brake line hose/tube (see accompanying illustration). Eliminate the cause of the blockage or replace the defective hose/tube.



The brake master cylinder nipple is blocked. Check and clean the cylinder and brake fluid reservoir.

Braking is applied too abruptly. Change your driving style.

Note. To check the brake mechanisms for jamming, jack up the car and place it on supports. Rotate each wheel by hand in turn. If the piston of the wheel hub/caliper of one of the brake mechanisms is jammed, it makes sense to check and perform a restorative repair of all cylinders/calipers, as well as the master cylinder.

The brakes failed

The master cylinder has failed. Remove the cylinder, perform its refurbishment, bleed the hydraulic system.

Brake fluid level has dropped due to leaking calipers/wheel cylinders. Perform necessary repairs, bleed the hydraulic system.

The fluid level has dropped due to leaks in the brake hoses/tubes. Replace defective components, bleed the hydraulic system.

Air has entered the hydraulic system. Find out and eliminate the cause, pump the system.

The brake fluid is contaminated. Empty the system, fill with fresh fluid, bleed the brakes.

Note: To find sources of leaks, fill the master cylinder with brake fluid and ask an assistant to pump the foot brake pedal. At the same time, try to visually register external fluid leaks.