CAR VIBRATES AT HIGH SPEEDS

SYMPTOM SUMMARY There is a vibration or shimmy at high speeds. The symptom may get worse as the vehicles speed increases and may or may not be present at lower speeds.USUAL CAUSE The usual cause of a vibration or shimmy at high speed is improper tire balance or damaged tires.DIAGNOSIS Perform a careful visual inspection of each tire. Look for damage to the tires such as bulges or exposed steel belts. Inspect the wheels for dents, warpage or missing lug nuts. Check the tire pressure to ensure all tires are inflated evenly and to the correct pressure (check the owner's manual for the correct tire pressure - it should also...

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BRAKE WARNING LIGHT IS ON

SYMPTOM SUMMARY The red brake warning lamp remains on after the vehicle is started. USUAL CAUSE The brake system is equipped with a red brake warning lamp that will illuminate under certain conditions. Some vehicles feature a float located in the master cylinder that will illuminate the brake warning lamp when the fluid level becomes too low. The light will also come on if hydraulic pressure is lost in one of the front or rear brake channels. Usually the proportioning valve contains the circuit that will turn the light on during hydraulic pressure failure. It will also automatically prevent any additional fluid to be...

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MASTER CYLINDER IS LOW ON BRAKE FLUID

SYMPTOM SUMMARY The master cylinder is low on brake fluid or the brake fluid continually goes low. USUAL CAUSE It is normal for the master fluid level to decrease slightly as the brake pads wear. As the brake pads wear, the pistons in the caliper extend to compensate for the friction wear. As this occurs, the caliper will store more brake fluid in the caliper cylinder and will decrease the fluid level in the master cylinder.DIAGNOSIS You will need to determine whether the fluid level is low in the master cylinder due to a fluid leak or the normal brake pad wear discussed above. A brake inspeciton should be...

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LOUD SQUEAL HEARD WHEN STEERING WHEEL IS TURNED

SYMPTOM SUMMARY A loud squeal is emitted from under the hood when the steering wheel is turned.USUAL CAUSE This symptom is usually caused by a loose or worn power steering belt.DIAGNOSIS With the help of an assistant, rotate the wheel all the way to the right or left while inspecting the drive belts. If the drive belts slip or squeal, service will be necessary. With the vehicle off, inspect the belts for wear or cracking. Some vehicles utilize a single serpentine belt that drives all of the accessories. These types of belts usually use an automatic tensioner that maintains the proper tension at all times....

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THERE IS A LIQUID ON THE FLOORBOARD OF MY CAR

SYMPTOM SUMMARYThere is a liquid present on the floorboard of the vehicle. The fluid may be green or clear and may be more noticeable after operating the heating or air conditioning system. USUAL CAUSE Water present on the floorboard is usually caused by one of two things. Water is circulated into the passenger compartment through the heater core. The heater core is heated by the engine coolant. Air is then blown over the heater core, by the blower motor when the heater is on, to heat the passenger compartment. If this core develops a leak, it will usually leak into the passenger compartment floorboard. A heater core that has only a pin-hole sized leak, may not be leaking on the floor but may produce a fine mist or oily film that collects on the...

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FRONT END DIPS WHEN I STEP ON THE BRAKES

SYMPTOM SUMMARY The vehicle dips forward when the brakes are applied.USUAL CAUSE This symptom is usually caused by misadjusted rear brakes or weak shocks or struts.DIAGNOSIS The shocks or struts can be tested by bouncing the front of the vehicle several times by placing your body weight on the front bumper. Once the vehicle starts the up and down motion, remove your weight from the front bumper. The up and down bouncing should come to a stop after only one or two additional bounces. If the the vehicle continues to bounce, the front shocks or struts may require replacement. A tire inspection can reveal worn...

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CAR PULLS WHEN I STEP ON THE BRAKES

SYMPTOM SUMMARY The vehicle pulls to the right or left when the brakes are applied.USUAL CAUSE The usual cause of this symptom is contamination on the braking surface or a malfunctioning caliper. It can also be caused by different tire sizes on the right and left wheels. Worn suspension components can also cause this symptom.DIAGNOSIS If contamination, such as grease or oil is present on the left side, the vehicle will pull to the right since the left side will not provide the same braking force as the right. A visual inspection is the first step in diagnosing the problem. Perform a visual inspection on both sides of...

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BRAKE PEDAL PULSATES WHEN I STEP ON IT

SYMPTOM SUMMARY The brake pedal pulsates when applied. The symptom may be worse at higher speeds. USUAL CAUSE This symptom is usually caused by warped brake rotors. If the vehicle is equipped with four wheel disc brakes, it could be either the front or rear brake rotors. Excessive heat build up on the brake rotors can cause them to warp , causing a brake pedal pulsation. This can be the result of heavy stop and go driving. If the rear brakes are not adjusted properly, the demand on the front brakes will be higher which can also contribute to front rotor warpage. Some vehicle brake designs are...

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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...

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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...

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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....

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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...

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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...

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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. ...

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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...

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CONTROL ARMS Et STEERING KNUCKLES

STEERING KNUCKLES The steering knuckle provides an attachment point for the tie rod to the wheel. The steering knuckle also provides an attachment point for the upper and lower ball joints in conventional A frame suspension system. With Macpherson strut systems, the steering knuckle anchors the lower end of the strut and the lower ball joint. The spindle of a rear wheel drive vehicle is supported and attached by the steering knuckle. With a front wheel drive vehicle, the front hub and bearing assembly is attached to the steering knuckle. Disc brake systems also use the steering knuckle as a mount for the brake caliper. The components...

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STEERING HUB

The hub and bearing assembly is attached to the spindle and steering knuckle of a vehicle's front suspension. The hub and bearings provide a rotation point for the wheel, as well as support for the weight of the vehicle on the spindle or axle. Rear wheel drive vehicles use tapered roller bearings for the front wheels. The wheel bearings are placed in the hub with the tapered ends facing one another. The inner bearing is larger than the outer bearing due to the need for increased support for the wheel. The outer races of the wheel bearings are pressed into the hub assembly. The wheel bearings are lubricated with bearing grease and...

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SQUEAK OR SQUEAL FROM WHEEL

SYMPTOM SUMMARY There is a squeak or squeal sound coming from the wheel area when the vehicle is in motion. The symptom may be worse when the brakes are applied.USUAL CAUSE A squeak or squeal from the wheel area can be caused by worn brake pads or uneven braking surfaces between the pad and the brake rotor. The brake pad is equipped with a metal wear indicator that contacts the brake rotor when the pads become worn beyond their useful service life. This wear indicator is designed to emit a high pitched squeak when it contacts the brake rotor to indicate that brake service is needed. If the brakes are severely worn, the indicator may contact the rotor at all times emitting the squeak even when the brakes are not applied.DIAGNOSIS A visual inspection of the brakes will indicate...

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Squealing Sounds

General Description of Problem: You hear a squealing sound at some point during the operation of your vehicle. Probable Explanation: Most squealing in an automobile comes from one of two locations. These are the belts or the brakes. Typical squealing from under the hood occurs when belts are slipping while brakes often squeal when either engaged in stopping or when the pads are worn to a low level and the "Warning Sensor" squeals to notify you it is time to get your brakes replaced. Solutions: 1. Determine if the squeal is under the hood or in the brake system. Common under the hood squeals can be heard immedietely after starting the car as the various belts kick into action, during use of the A/C system, or while turning in a car with power steering. If the squeal...

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SHOCKS AND STRUTS

STRUTS AND SHOCKS Struts and shocks are used for ride control in the suspension system of a vehicle. They are designed to dampen the movement of the vehicle suspension as it reacts to changes in road surface. Shock absorbers are used with conventional coil spring, leaf spring or torsion bar suspension systems. Shocks serve to control the rebound action of the springs or torsion bars. Shock absorbers contain a large piston rod, hydraulic oil and a control valve. When the shock absorber compresses, the piston rod tries to force the hydraulic oil through an orifice in the control valve. The diameter of the...

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RACK AND PINION STEERING

The steering gear transfers the rotary motion of the steering wheel to a linear motion used to steer the front wheels. Two types of steering gear are in use today, the standard gear box and the rack and pinion. The standard gear box uses a worm gear that is rotated by the steering wheel to move the pitman shaft. The worm gear contains spiral cut grooves that mesh with a sector gear at the top of the pitman shaft. The spiral action of the worm gear causes the pitman shaft to move the steering linkage in a linear motion. Power steering is achieved by using hydraulic pressure to assist in the rotation of the worm gear. ...

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EMERGENCY BRAKE

The emergency or parking brake is used as a mechanical means to apply the rear brakes for parking or in the event of failure of the brake hydraulic system. Application of the emergency brake is accomplished through a hand or foot operated lever. The operating lever contains a ratchet assembly that allows the brake to be locked in place. A brake warning light switch is connected to the parking brake lever assembly and is used to illuminate the brake lamp when the emergency brake is applied. Diagnosing problems involving the parking brake are fairly straightforward. Refer to your auto repair book for the design details pertaining...

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THE MASTER CYLINDER

All passenger cars and light trucks in the United States today are equipped with a dual master cylinder. The dual master cylinder, also known as a tandem master cylinder, is essentially two separate master cylinders combined into one unit. The dual master cylinder is used as a safety device, to divide the brake hydraulic system into two individual hydraulic circuits. There are two types of split hydraulic systems used. Most rear wheel drive vehicles use a conventional split system, dividing the brake circuits by axle. One half of the master cylinder is used to operate the front brakes, while the other is used to operate...

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JOINTS AND BOOTS

The efficient operating range of a universal joint is about 1-4. When this range is exceeded, the universal joint will start to vibrate excessively. This is caused by the universal joint speeding up and slowing down as it rotates. It is a normal operating characteristic of a universal joint, and is minimized by using the front universal joint to cancel out the rear universal joint. However, this will only work if the universal joint operating angle does not exceed 5 degrees. As the angle increases, the speed fluctuation of the universal joint, as it rotates, rises beyond acceptable limits. Because of this, universal joints are...

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EMERGENCY BRAKE OR PARKING BRAKE WON'T HOLD

SYMPTOM SUMMARY The emergency brake or parking brake will not hold.USUAL CAUSE The usual cause of this symptom is improper rear brake adjustment. Many vehicles utilize a self adjusting rear brake system. This system maintains adequate brake tension on the rear brakes so that when the parking brake is engaged, the rear brakes hold the vehicle in place.DIAGNOSIS The self adjusters re-tension the rear brakes each time the parking brake is engaged or the vehicle is driven in reverse and the brakes are applied. This system needs to be used frequently to maintain the proper rear brake tension. Often, the parking...

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I HEAR A LOUD SQUEAL WHEN A/C IS TURNED ON

SYMPTOM SUMMARY A loud squeal is produced when the A/C is turned on.USUAL CAUSE This symptom is usually caused by a loose or worn air conditioning compressor belt. When the A/C is activated the compressor is engaged. This places a load on the engine and the drive belt that rotates the compressor. If the belt is loose or worn the belt can slip on the compressor pulley and emit a loud squeal.DIAGNOSIS The drive belts should be inspected for proper tension and wear. A properly tensioned belt should have aproximately 1/2" of deflection at its greatest span between pulleys. Inspect the belt for wear. Belts can become glazed on the inside drive surface which can cause them to slip, which produces the loud squeal. Some vehicles use an automatic tensioner that contains a large spring...

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CAR PULLS TO ONE SIDE WHILE DRIVING

SYMPTOM SUMMARY The vehicle pulls to the right or left. The problem may be worse at higher speeds. If the symptom only occurs during braking, refer to the "Vehicle Pulls When Brakes Are Applied" symptom.USUAL CAUSE This symptom usually indicates that a front end alignment is needed. It can also be caused by a tire pull or improperly inflated tires.DIAGNOSIS Tire pressure and condition should be checked and corrected as necessary. The tires should be rotated from front to rear and the vehicle should be road tested. If the symptom still persists, the front end alignment will have to be inspected and adjusted as necessary.PRECAUTIONS,...

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BRAKE WARNING LIGHT

The brake warning light is located in the instrument cluster area and is illuminated to warn of brake pressure loss or to indicate application of the parking brake. The brake warning light is supplied voltage from an ignition feed circuit and ground is furnished through two separate switches to illuminate the light. One switch is located in the brake combination valve or the master cylinder. In the event of a failure of one of the hydraulic circuits of the brake system, the switch will close and the light will be illuminated. The other switch is used to warn of parking brake application and is located near the parking brake lever....

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Brake System Overview

Early automobile brake systems consisted of cable operated brake lining, usually mounted on one axle. The system provided extremely poor stopping power and did not always apply brake pressure evenly to the wheels. This could cause one wheel to lock up and make the vehicle difficult to control during stops. Front brakes were rarely equipped on early vehicles. The need to have the front wheels move from side to side for steering made installation of a cable operated brake system an engineering nightmare. The invention of hydraulic brake systems provided safe, high powered and even braking for automobiles and light trucks. Hydraulic...

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THE BRAKE SYSTEM

BRAKE SHOES Vehicles equipped with a drum brake system use brake shoes to stop the vehicle, by creating friction between the brake lining and the inside surface of the brake drum. The brake shoes consist of heat resistant friction material, bonded or riveted to a metal shoe. Hydraulic pressure is applied to the wheel cylinder which forces the brake shoe into the brake drum. Diagnosing and troubleshooting automotive brakes and doing the necessary repairs is a very doable task as brakes are not difficult to understand and most of the components are easily accessible.There are two basic types of drum brake lining arrangements used on...

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BRAKE ROTOR AND CALIPER

One of the more doable jobs in auto repair is that which involves the brakes. The brake rotor provides a friction surface for the brake pads. It is designed to dissipate the heat generated by friction during braking. The ability of a brake rotor to properly disperse heat relates to the size of the brake rotor. The measurement of the thickness of the brake rotor is designed to provide the greatest heat dissipation possible. Machining the brake rotor below those specifications can cause excessive heat build-up during heavy braking. The brake rotor may have cooling fins set in the center to provide ventilation for improved heat dissipation....

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