THE BRAKE PEDAL GOES TO THE FLOOR WHEN I STEP ON IT

SYMPTOM SUMMARY
The brake pedal goes to the floor when pressed. There may be little or no braking action when the pedal is depressed. The Red Brake Warning Lamp may be illuminated indicating a system failure.

USUAL CAUSE
Very low brake fluid or a defective Master Cylinder is the usual cause of this symptom. The master cylinder pressurizes the brake system when the pedal is depressed and provides hydraulic fluid to each of the wheels to apply the brakes. The braking system is designed to illuminate the Red Brake Warning lamp when a hydraulic failure is present.

DIAGNOSIS
If you have just performed other brake work on the vehicle and the hydraulic system was opened, the most probable cause is air in the system. The system will need to be bled according to manufacturers recomendations. The first step in diagnosing this symptom is to inspect the brake fluid level at the master cylinder. If the fluid level is low, the system will need to be inspected for leaks. The calipers, wheel cylinders (on drum brakes) will need to be inspected. Brake pads that are completely worn can cause low fluid level. This is a result of the caliper pistons being completely extended, causing most of the brake fluid to reside in the calipers. The brake pads and shoes (if equipped) should be inspected for signs of brake fluid contamination indicating a leak. Inspect the calipers for leaks at the rubber dust boot around the pistons. The dust boot on the wheel cylinder will have to be pulled off slightly to inspect for leaks. Check the hydraulic lines, proportioning valve and flexible hoses for leaks. Inspect the master cylinder where it mounts on the brake booster for signs of leaks. Loosening the master cylinder retaining bolts and pulling it back slightly, will usually result in detection of a leak if present. If leaking, the fluid will run out of the mating surfaces. In this case, the master cylinder will require replacement. If there are no fluid leaks present or the fluid level is normal and the brake pads and shoes (if equipped) are in good condition, the most probable cause of the symptom is a defective master cylinder.

CORRECTIVE ACTION Determining the cause of the failure will dictate what corrective action is necessary. If the hydraulic system needs to be serviced, as with replacement of the master cylinder, it will need to be bled of all the air once it has been resealed. Refer to the manufacturers specific bleeding procedures.

PRECAUTIONS, TIPS, and NOTES
If the vehicle is equipped with ABS, certain ABS components can cause this symptom. In this case, the system should be serviced according to manufacturers recommendations. If servicing the hydraulic system, use caution not to contaminate the system with dirt, debris or water. Always use the recommended brake fluid DOT rating. This information can be obtained from your owners manual or off the cap on the master cylinder.

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BRAKES MAKE A GRINDING NOISE WHEN APPLIED

SYMPTOM SUMMARY
The brakes emit a grinding noise when applied. The braking action may not be as effective as normal.

USUAL CAUSE This symptom is usually caused by metal to metal contact between the brake pad and rotor or brake shoe and drum. The brake pads and shoes have a metal surface that the friction surface is mated to. Once the friction material is worn off, the metal surface will contact the rotating surface of the drum or rotor. This metal to metal contact usually results in a grinding noise.

DIAGNOSIS A visual inspection of the brake system will indicate the cause of the noise. The brake pads and rotors should be inspected for damage. If the rotor is excessively worn beyond the manufacturers minimum thickness, the rotor will have to be replaced. If the drums have grooves worn in them beyond the manufacturers maximum diameter, they will require replacement.

PRECAUTIONS, TIPS, and NOTES When replacing the brake pads or shoes, it is recommended that the brake rotors and drums be machined (often referred to as surfaced or turned). This will provide a flat mating surface for the new pads or shoes which will prevent brake squeal. A high quality anti-squeak compound should be applied sparingly to the back side of the new pads. Some vehicles use metal shims between the pad and the caliper. These shims should be replaced or cleaned and re-installed. Brake rotors and drums become extremely hot after vehicle operation and braking. Use caution when working on the braking system. Brake rotors and drums have a manufacturers minimum thickness and maximum diameter specifications. Never machine a rotor or drum beyond the manufacturers specifications. The minimum thickness and maximum diameter specification is usually stamped on the brake rotor or drum.

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ODOR COMING FROM AIR CONDITIONING VENTS

SYMPTOM SUMMARYA mild to severe odor that emanates from the air conditioning vents shortly after starting the air conditoning. The odor may diminish after the air conditioner has been running for several minutes but reoccurs at next operation.

USUAL CAUSE Odor from the air conditioning is usually caused by mildew growth on the air conditioning evaporator core. During normal A/C operation, water condenses on the evaporator core. This water is drained off through a tube located at the bottom of the evaporator housing in the passenger compartment. Small amounts of water will remain on the evaporator core after the air conditioning is turned off. On a hot day, this moisture inside the evaporator case can cause mildew growth on the evaporator core. This mildew growth can cause a foul odor through the air conditioning vents during the first few minutes of air conditioning operation. It can smell like dirty feet or stinky socks.

CORRECTIVE ACTION
There are several industrial chemicals that can be used to kill the mildew growth, but it will usually require perodic treatments at the peak of the air conditioning season. Household mildew sprays can also help by spraying a fine mist into the vent inlets, usually located on the exterior of the vehicle near the windshield. This procedure should be done while the fan is on high, all windows in the vehicle open and the recirculation switch on the dash set to outside air. The purpose is to draw the cleaner past the evaporator core killing any mildew present on the surface. Use the cleaner sparingly and never spray it directly into the vents located in the passenger compartment.

PRECAUTIONS, TIPS, and NOTES
Completely ventilate the vehicle of any cleaner fumes prior to driving with the windows up. Use caution with the cleaner not to damage the paint or interior of the vehicle.

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ANTI-LOCK BRAKE LIGHT STAYS ON AFTER ENGINE IS STARTED

SYMPTOM SUMMARY
The "ABS" or "Anti-Lock Brakes" light remains on after the engine is started and remains on or flashes.

USUAL CAUSE
The Anti-Lock brake system is designed to rapidly modulate the braking action during a panic stop. This prevents the wheels from locking up and maintains vehicle control and stability. An ABS control module monitors the wheel speed and other various sensors to determine when wheel lock-up is about to occur. The ABS module continually performs diagnostics to ensure that the system is functional. When a malfunction occurs, the ABS module will illuminate or flash the ABS or Anti-Lock light on the dash panel to alert the driver. During start up, the module will illuminate the light as a self test. Shortly after the engine is started, the light should go out indicating the system is functional. If the light remains on the ABS Module has detected a system failure. On most vehicles, the ABS system will not be functional while the light is illuminated. Usually, normal braking will result unless the failure is related to a component that is used for both normal braking and anti-lock braking. If the Red Brake light is also on, normal braking may be degraded as well indicating a system wide failure.

DIAGNOSIS
On almost all ABS systems the module will store a diagnostic trouble code that relates to the circuit or component that has failed. The diagnosis will require the module to be placed in self diagnostic mode, which will result in it transmitting the stored diagnostic code. Once the code is received, the diagnosis should focus on that particular component or sensor. A vehicle specific service manual will indicate how the module is placed into diagnostic mode and will indicated what circuit or component relates to what code. Often a special scan tool, similar to a hand held computer, is required to interface with the module.

CORRECTIVE ACTION Once the code has been retreived from the modules memory, that component or circuit will require service. Some components, such as the wheel speed sensors, are usually simple to replace. However, other components such as the hydraulic modulator and control solenoids require special tools and special bleeding procedures to ensure proper operation.

PRECAUTIONS, TIPS, and NOTES
If the ABS light is on, the failure should be corrected as soon as possible. If possible, you should leave repairs to the ABS system to trained service personnel that are equipped with the correct tools and equipment. The Hydraulic Modulator may contain brake fluid pressurized to over 1,500 psi, that if not properly bled, can pose significant danger to someone servicing the system.

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THE TORSION BAR

TORSION BARS
Torsion bars provide spring action for the front suspension from the twisting of a metal bar. Torsion bars are anchored to the frame at one end and attached to the lower control arm at the other. The weight of the vehicle along with the movement of the control arm causes the rod to twist. The twisting of the metal rod provides a torsional spring that reacts in a similar manner to the coil spring. Ride height is controlled through use of an adjustable arm at the frame mounting point for the torsion bar.

AUTOMATIC LEVEL CONTROL
Automatic level control provides automatic adjustment of a vehicles ride height to compensate for load or driving conditions. Components consist of a level controller, air pump, air shocks or air bags and ride height sensors. The system works by using sensors to input information about the ride height of a vehicle to the controller. The controller then supplies air from the air pump to the air shocks or air bags, as necessary to adjust the vehicles ride height as needed.

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SUSPENSION AND TIRES

SUSPENSION OVERVIEW
The suspension of a vehicle is used to allow the tires to react to changes in the road surface and support the chassis of the vehicle. The suspension allows the wheels to move up and down while dampening the transfer of this movement to the rest of the vehicle, including the occupants. Independent suspension is used in the front ends of passenger cars and most light trucks. Some vehicles use four wheel independent suspension. Independent suspension allows one wheel to react to surface variation without affecting the other wheels. Each wheel is attached to the chassis using individual suspension components.

TIRES
The tires of an automobile provide traction for starting, stopping and driving. They are used to support the weight of a vehicle and as an aid to the operation of the vehicles suspension. Passenger car tire sizes in the U.S. today, are rated in the P-Metric system. The rating can be found on the side wall of the tire. This is an alpha-numeric rating system that uses a letter or number to represent size, usage or construction of a tire. An example is P215/75R15. The first letter is an indication of the usage of the tire, P would stand for passenger car, LT would be a light truck. 215 is a rating in millimeters for the section width of a tire. The number after the slash represents the aspect ratio of the tire and the tires sidewall height in relation to its width. The R designates the construction of the tire, in this case it stands for radial. If a letter were to preceded this letter, it would indicate a speed rating of the tire. The last number indicates the rim size that the tire is intended for.

Other information that can be found on the tire side wall is the Uniform Tire Quality Grading designation. This is a government tire rating system used by manufacturers to provide tire comparison information. With the UTQG rating system, information is given to compare tire treadwear, traction and temperature resistance. Treadwear is a measure of tire durability. 100 would be a tire rated for standard resistance to treadwear. A rating of 300 would be a tire with three times the treadwear resistance of a standard tire. This rating should be used to compare tire treadwear within a manufacturer, not between manufacturers.

The traction rating is a grade classifying a tires ability to stop in a straight line on wet surfaces, concrete and asphalt under test conditions. An A rating means the tire meets maximum DOT standards. A B rating means the tire meets medium DOT requirements. A C rating indicates a tire meets minimum requirements. There are three grades used to measure a tires resistance to generation of heat due to friction. Grade A indicates a tire that can withstand temperatures generated at 115 mph for 30 minutes. Grade B indicates a tire that can withstand temperatures generated at 100 mph for 30 minutes. Grade C indicates a tire that cannot withstand temperatures generated at 100 mph for 30 minutes.

Tire wear is affected by driving conditions, wheel alignment, balance and inflation pressure. Proper maintenance is the best way to insure longer tire life. Inflation pressure should be checked weekly. Tire rotation schedules should be followed as recommended by the manufacturer. Wheel alignment should be checked if uneven tire wear is noticed or after running over a large hole or object. Aggressive driving should be avoided to extend tire life as well.

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STEERING SYSTEM OVERVIEW

POWER STEERING PUMP
The power steering pump provides the hydraulic pressure used for steering assistance. The power steering pump is driven by a belt attached to the crankshaft pulley. The power steering pump pulley rotates a vane assembly inside a pump ring located inside the pump. Pressure is created by compressing fluid between the vanes and the surface of the pump ring. The pump pressure output is maintained by a flow control valve that contains an internal pressure relief valve. There are two types of power steering pumps used, submerged and nonsubmerged. Both are similar in operation, with the only difference being the type of fluid reservoir used. A submerged type of pump contains the pump and fluid reservoir in one unit. A nonsubmerged uses a remote fluid reservoir for the pump.

STEERING COLUMN/SHAFT
The steering column is a link between the steering wheel and the steering gear. It consists of a collapsible housing containing a collapsible rotating shaft. As a safety measure, the steering column is designed to collapse in the event of a front end collision. If a steering column has collapsed, it must be replaced. The steering shaft is a two piece component located inside the steering column. It is supported at the top and the bottom of the steering column by bearings. The steering column housing may also contain transmission shift components. Design of transmission shift components can vary from model to model. Earlier models use a tube that contained a rod that runs the length of the column used to actuate shift linkage. Recent model vehicles use a cable operated shift linkage, that can be actuated by a column mounted shift lever. Safety designs on late model vehicles incorporate a brake transmission shift interlock system. This system locks out shifter operation, when the ignition is on, until the brake pedal is depressed. Most systems use an electric solenoid actuated by the brake light switch, that releases the shift linkage. The steering column is used to mount several accessories. The turn signal switch, headlamp dimmer switch, wiper switch, and ignition switch, can be located on or inside the steering column. Service of the steering column usually requires removal of these components. Care should be taken when the steering column is removed for service. The column should not be dropped, leaned on, or subject to blows to either end. Internal components of the column can shear off, causing the column to partially collapse.

TIE RODS
The tie rods are used to link the steering gear to the steering knuckle. The tie rod ends are a ball and socket design that allows the tie rod to flex up and down with the movement of the front suspension. Tie rods should be inspected for excessive movement, grease seal tears, or any visible wear. You should not be able to collapse the ball and socket assembly of the tie rod by attempting to compress it by hand. Any inward movement of the ball and socket should be considered excessive wear.

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