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Monday, 27 October 2014

Brake System

Brake System Points : Brake System, Brake System Inspection, Check Brake Pedal Action, Brake Pedal Height, Brake Pedal Free Play, Brake Pedal Reserve Distance, Checking Brake Fluid, Check For Brake System Leaks, Check Parking Brake, Checking Brake Assemblies, Brake System Inspection Approximately all of the automobile manufactures recommend a periodic inspection of the brake system. This involves checking brake pedal action, fluid level in the master cylinder and the condition of the brake lines, hoses and wheel brake assemblies. The inspection is a part of preventive maintenance, which assures vehicle safety.
Check Brake Pedal Action A fast and accurate way of checking many components of the brake system is the brake pedal check. This is done by applying the brake pedal and comparing its movement to the specifications. The three brake pedal application (specifications) are:
1. Pedal height
2. Pedal free play
3. Pedal reserve distance.
1. Brake Pedal Height It is the distance from the pedal to the floor with the pedal at rest. If the height is in correct. It usually points to the Problems in the pedal mechanism. There may be worn pedal bushings, weak return springs or maladjusted master cylinder push rod. 2. Brake Pedal Free Play It is the amount of pedal movement before the beginning of brake application.
It is the difference between the “at rest” and initially applied positions. Brake pedal free play is needed to prevent brake drag and over heating. If pedal free play is not correct, check the adjustment of the master cylinder push rod. A worn pedal bushing or a bad return spring can also increase pedal free play.
3. Brake Pedal Reserve Distance It is measured from car floor to the brake pedal with the brakes applied. Typically, brake pedal reserve distance should be 2 (051mm) for manual brakes and one inch (25mm) for power brakes. If brake pedal reserve distance is incorrect, check push rod adjustment. Also these may be air in the system or brake adjuster may not be working. Many other problems can cause incorrect pedal reserve distance.
When checking brake pedal action, apply and hold the brake pedal firmly for about 15 minutes seconds. The engine should be running if the car has power brakes. Try to defect any system leakage, which would cause the pedal to slowly move towards the floor. Also make sure the pedal is firm and returns properly. While checking the brake pedal, you should also make sure the brake lights are operating. If they do not work, check the bubbles, fuses and switches.
Checking Brake Fluid An important part of brake system inspection is checking the level and condition of the brake fluid. To check the fluid, remove the master cylinder cover. Pre off be spring clip or unbolt the cover. The brake fluid level should be ¼ inch (6 mm) from the top of the reservoir (typically). Caution Use only the manufactured recommended type of brake fluid. Also keep oil grease and other substances out of the brake fluid contamination can cause rapid deterioration of the master cylinder cups. A sudden loss of braking ability could result. Check For Brake System Leaks When the fluid level in the master cylinder is low, you should inspect the brake system for leaks. Check all brake lines hoses and wheel cylinders. Brake oil leakage will show up as a darkened, damp area around one of the components. Verify brake system leakage by checking that the leaking fluid smells like brake fluid. Check Parking Brake Apply the parking brake, the pedal or level should not move more than 2/3 of full travel. The parking brake should keep the car from moving with the engine idling in drive. The cables and linkage also should be inspected. The cables should not be frayed. The linkage should be tight, undamaged and well lubricated. Checking Brake Assemblies When inspecting a brake system, remove one of the front and rear wheels. This will let you inspect the condition of the brake linings and other components. When inspecting disk brakes, check the thickness of the brake pad linings. Pads should be replaced when the thinnest (most worn) part of the lining is not thicker than the metal shoe (approximately 1/8 or 3mm).
Check the caliper piston for fluid leakage and disc for damage. The disc should not be scored, creaked or heat checked (over heating causes small hardened and cracked areas) the wheel bearings should be adjusted properly. To check the rattles, strike the caliper with a rubber mallet. Repair any of these problems following a service or workshop manual.
When inspecting drum brakes, you must remove the brake drum. This will expose the brake shoe linings, wheel cylinders, braking service of the drum, adjuster enchains and other parts.
The brake shoe lining must not be worn thinner than approximately 1/16” (1.6mm). The shoes should not be glazed or coated with brake fluid, grease, or differential fluid. Any of these problems require lining replacement.
Pull back the wheel cylinder boots and check for leakage. If the boot is full of fluid the wheel cylinder should be rebuilt or replaced. Also check the automatic adjuster, return springs and brake drum. The brake drum should not be, scored, cracked, leak checked or worn beyond specification.
Danger Do not use compressed au to below brake dust off a wheel brake assembly because the most brake linings are made of asbestos, a known cancer causing substance. Use a special brake vacuum machine and a clean rag to remove the dust. Take every precaution, not to breath brake lining dust. If needed wear an approved filter mask over your nose and mouth.

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