Brake System Trouble Shooting

NOTE: This is a general trouble shooting guide. Not all steps will apply to all brake systems. When using this guide, locate the condition in column one that corresponds to your problem and determine the possible causes in column two. Match the number of the possible causes with the same number in column three.

CONDITION	POSSIBLE CAUSE	CORRECTION
Brake chatter, squeal, squeak	1) Dust on drums/rotors, oil stained linings	1) Remove drum/rotor, clean
	2) Weak shoe return spring	2) Check, replace springs
	3) Drum out of round	3) Turn drum on lathe
	4) Excessively worn pads or shoes	4) Replace pads or shoes
	5) Uneven rotor surface	5) Check rotor surface in various locations with micrometer
	6) Excessive lateral rotor runout	6) Check runout with dial indicator, resurface or replace rotor
	7) Excessive wheel bearing play	7) Readjust or replace bearings
Excessive pedal travel	1) Excessive rotor runout	1) Check rotor with dial gauge, resurface or replace
	2) Brake fluid boil	2) Drain system, refill with fluid of correct specification
	3) Warped or excessively worn pads or shoes	3) Check and replace pads or shoes
	4) Rear brakes out of adjustment	4) Adjust shoe to drum clearance
	5) Power brake unit malfunction	5) Check and either overhaul or replace unit
Poor brake operation	1) Too long brake lever stroke	1) Readjust brake pedal lever
	2) Brake cable sticking	2) Check brake cable routing and lubricate
	3) Excessive shoe to drum clearance	3) Check self-adjuster mechanism; readjust or replace components
Shock when pedal applied	1) Brake drum cracked or distorted	1) Replace drum
	2) Uneven brake drum wear	2) Resurface drum or replace
	3) Broken return spring	3) Replace springs
Leaks in caliper piston cylinder	1) Damaged or excessively worn caliper piston seal	1) Overhaul caliper and install new seals
Leaks in caliper piston cylinder	2) Deep scores or corrosion on surface of cylinder bore	2) Overhaul caliper and hone (unless not recommended by manufacturer); install new seals
Rattling in front brakes	1) Pad anti-rattle spring clip broken or missing	1) Install new part or reposition existing one
Rattling in front brakes	2) Excessive clearance between pads and caliper	2) Fit caliper with new pads
Pull when brake applied	1) Incorrect tire pressure	1) Inflate tires evenly as indicated in owners manual
	2) Front end out of alignment	2) Check and align front end
	3) Unmatched tires	3) Make sure all tires have approximately equal amounts of tred and pressure
	4) Restricted brake lines or hoses	4) Inspect for soft hoses or damaged lines. Replace with new hoses or brake tubing
Excessive pedal pressure required	1) Linings coated with brake fluid, oil or grease	1) Fit new pads or shoes
	2) Entire pad not contacting rotor	2) Replace pads
	3) Scored brake rotors	3) Resurface rotor according to specs.
	4) Incorrect pads	4) Check pads
	5) Seized piston	5) Overhaul caliper, check piston
	6) Power brake failing	6) Check power unit and replace
Low pedal effect	1) Air in hydraulic system, brakes not properly bled	1) Check for air leaks and bleed hydraulic system
	2) Hydraulic fluid leaking past primary cup in master cylinder	2) Overhaul master cylinder making sure to replace cups
	3) Bleeder screw not tight	3) Tighten bleeder screw
Uneven braking	1) Linings contaminated	1) Clean or refit with new pads/shoes
	2) Unmatched disc pads	2) Ensure all pads on any axle are same quality
	3) One or more seized pistons	3) Overhaul caliper to free piston
	4) Incorrect tire pressure	4) Inflate tires according to manufacturers recommendations
	5) Front wheel out of alignment	5) Align front wheels
	6) Brake hose or line clogged	6) Free restriction
	7) Caliper alignment improper	7) Remove and realign caliper
Brake pedal pulsation	1) Excessive rotor lateral runout	1) Check rotor runout with dial gauge
	2) Rotor not parallel	2) Check rotor and replace
	3) Wheel bearings out of adjustment	3) Adjust
	4) Rear drums out of round	4) Check drums and turn or replace
Spongy pedal	1) Air in brake system	1) Bleed system
	2) Swollen brake hose(s)	2) Replace hose and bleed system
	3) Brake fluid boiling point too low	3) Drain, flush and refill with fluid of proper specifications
	4) Filler cap vent hole plugged	4) Clean, then bleed system
Pedal yield under slight pressure	1) Deteriorated check valve	1) Replace valve, bleed system
	2) External brake fluid leaks	2) Check master cylinder, lines, and wheel cylinders; replace
	3) Internal leak in master cylinder	3) Overhaul master cylinder
Brake failure or heavy pedal	1) Power unit diaphragm damaged	1) Check and/or replace diaphragm
	2) Check valve malfunctioning	2) Replace valve
	3) Defective vacuum hose	3) Replace hose
	4) Twisted air valve and valve rod plunger	4) Disassemble and repair
Brakes react slowly	1) Check valve malfunction	1) Clean or replace check valve
	2) Vacuum hose blocked or broke	2) Replace hose
	3) Air cleaner clogged or restricted	3) Clean or replace air cleaner
Brake drag or slow return	1) Push rod out of alignment	1) Disassemble and repair
	2) Operating rod out of adjustment	2) Adjust
	3) Air valve and push rod plunger twisted	3) Adjust