Chevrolet Sonic Repair Manual: Brake Assist System Description and Operation
- System Component Description
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The brake assist system consists of the following:
- Brake Pedal
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Receives, multiplies and transfers brake system input force from driver.
- Brake Pedal Pushrod
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Transfers multiplied input force received from the brake pedal to the vacuum brake booster.
- Vacuum Brake Booster
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Uses source vacuum to decrease effort required by driver when applying brake system input force. At rest, source vacuum is applied to both sides of the vacuum diaphragm for single booster. Return springs maintain the booster in a rest position. When brake system input force is applied, vacuum to the rear of the diaphragm is cut off, and air at atmospheric pressure is admitted in its place. This provides a decrease in brake pedal effort required. When input force is removed, vacuum again replaces atmospheric pressure within the booster.
- Vacuum Source
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Supplies force used by vacuum brake booster to decrease brake pedal effort. The source vacuum for a spark ignition engine is normally derived from the intake manifold.
- Vacuum Source Delivery System
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Enables delivery and retention of source vacuum for vacuum brake booster.
- System Operation
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Under normal driving conditions, without the brakes applied, vacuum is allowed to act on both sides of the diaphragm within the vacuum brake booster. When the brake pedal is applied, the effort by the driver is multiplied due to the relative length of the brake pedal in relationship to its pivot point and the point at which the push rod to the vacuum brake booster is attached.
Movement of the push rod causes a valve within the vacuum brake booster to close between the two sides of the diaphragm, thus isolating each side. It also allows a valve to open that allows atmospheric pressure to act on the pedal side of the vacuum brake booster while maintaining vacuum on the vacuum source side of the diaphragm. The movement of the brake pedal pushrod is transferred to the hydraulic brake master cylinder via the vacuum brake booster. The pressure differential within the vacuum brake booster reduces the effort required by the driver in applying the brakes.
General
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Brake Dust Warning
Warning: Avoid taking the following actions when you service wheel
brake parts:
Do not grind brake linings.
Do not sand brake linings.
Do not clean wheel brake parts with a dry brus ...
Other materials:
Eliminating Unwanted Odors in Vehicles
GM Vehicle Care Odor Eliminator, Refer to Adhesives, Fluids, Lubricants, and
Sealers, may control or eliminate odors in the interior and luggage compartment
areas of GM vehicles. This non-toxic, biodegradable, odorless product has been shown
to greatly reduce or remove the following types of o ...
Rear Compartment Courtesy Lamp Replacement (Hatchback)
Rear Compartment Courtesy Lamp Replacement
Callout
Component Name
1
Rear Compartment Courtesy Lamp Assembly
Procedure
Use the appropriate trim tool in order to release the lamp assembly
from the rear quarter ...
Cylinder Head Removal
Loosen the 12 cylinder head bolts in the sequence as shown. Use the following
procedure:
Loosen the cylinder head bolts 90 degrees.
Loosen the cylinder head bolts 180 degrees.
Note: Do not damage the guide sleeves (4) and (5).
R ...
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