Service Manual2007 Aveo HYDRAULIC BRAKES

SECTION 4A

HYDRAULIC BRAKES

Caution : Disconnect the negative battery cable before removing or installing any electrical unit or when a tool or equipment could easily come in contact with exposed electrical terminals. Disconnecting this cable will help prevent personal injury and damage to the vehicle. The ignition must also be in LOCK unless otherwise noted.otherwise noted.

SPECIFICATIONS

General Specifcations

Application	Millimeters	Inches
Brake Drums:	.	.
Inside Diameter	200.00	7.87
Maximum Revore Diameter	201.00	7.91
Out-to-Round	0.04	0.001
Brake Rotors:	.	.
Discard Thickness	18.00 (22*)	0.71 (0.86*)
Lateral Runout (Installed)	0.06	0.002
Rotor Diameter	236.00 (256*)	9.29 (10.08*)
Rotor Thickness (New)	20.00 (24*)	0.79 (0.94*)
Thickness Variation	0.1	0.004
Master Cylinder:	.	.
Bore Diameter	22.22	0.87
Minimum Bore Diameter	20.64	0.81
Caliper	.	.
Piston Minimun Diameter	52 (54*)	2.05 (2.12*)
Wheel Cylinder Diameter:	.	.
Front	52 (54*)	2.05 (2.12*)
Rear	20.64	0.81

* : Optional (High Altitude or 1.6L DOHC)

Fastener Tightening Specifications

Application	N•m	Lb-Ft	Lb-In
Frint brake hose-to-caliper bolt	40	30	354
Bleeder Screw	9	7	80
Caliper Maunting Bolt	100	74	885
Hub-to-Disc Screws	4.5	3.3	40
Dust Cover Screws	4.5	3.3	40
Brake Lines	16	12	142
Trim Panel Screws	7	-	62
Brake Pedal-to-Pedal Bracket Hex nut	22	16	-

COMPONENT LOCATOR

Brake System - ABS -

Brake oil tank cap
Brake oil tank
Master cylinder
Brake booster
Brake booster nut
Pedal bolt
Pedal
Pedal nut
Spring
Brake pedal cover
Pedal bracket assembly
Stoplamp switch
Front brake pipe
Rear brake pipe
Front brake hose
Rear brake hose
E-ring
Union bolt
ABS assembly

Brake System - NON-ABS -

Brake oil tank cap
Brake oil tank
Master cylinder
Brake booster
Brake booster nut
Pedal bolt
Pedal
Pedal nut
Spring
Brake pedal cover
Pedal bracket assembly
Stoplamp switch
Front brake pipe
Rear brake pipe
Front brake hose
Rear brake hose
E-ring
Union bolt

DIAGNOSIS

Brake System Testing

Brakes should be tested on a dry, clean, reasonably smooth and level roadway. A true test of brake performance cannot be made if the roadway is wet, greasy, or covered with loose dirt whereby all tires do not grip the road equally. Testing will also be adversely affected if the roadway is crowned so as to throw the weight so roughly that the wheels tend to bounce.

Test the brakes at different vehicle speeds with both light and heavy pedal pressure; however, avoid locking the brakes and sliding the tires. Locked brakes and sliding tires do not indicate brake efficiency since heavily braked, but turning, wheels will stop the vehicle in less distance than locked brakes. More tire-to-road friction is present with a heavily braked, turning tire than with a sliding tire.

Because of the high deceleration capability, a firmer pedal may be felt at higher deceleration levels.

There are three major external conditions that affect brake performance:

Tires having unequal contact and grip of the road will cause unequal braking. Tires must be equally inflated, and the tread pattern of the right and the left tires must be approximately equal.
Unequal loading of the vehicle can affect the brake performance since the most heavily loaded wheels require more braking power, and thus more braking effort, than the others.
Misalignment of the wheels, particularly conditions of excessive camber and caster, will cause the brakes to pull to one side.

To check for brake fluid leaks, hold constant foot pressure on the pedal with the engine running at idle and the shift lever in N (Neutral). If the pedal gradually falls away with the constant pressure, the hydraulic system may be leaking. Perform a visual check to confirm any suspected leaks.

Check the master cylinder fluid level. While a slight drop in the reservoir level results from normal lining wear, an abnormally low level indicates a leak in the system. The hydraulic system may be leaking either internally or externally. Refer to the procedure below to check the master cylinder. Also, the system may appear to pass this test while still having a slight leak. If the fluid level is ormal, check the vacuum booster pushrod length. If an incorrect pushrod length is found, adjust or replace the rod.

Check the master cylinder using the following procedure:

Check for a cracked master cylinder casting or brake fluid leaking around the master cylinder. Leaks are indicated only if there is at least one drop of fluid. A damp condition is not abnormal.
Check for a binding pedal linkage and for an incorrect pushrod length. If both of these parts are in satisfactory condition, disassemble the master cylinder and check for an elongated or swollen primary cylinder or piston seals. If swollen seals are found, substandard or contaminated brake fluid should be suspected. If contaminated brake fluid is found, all the components should be disassembled and cleaned, and all the rubber components should be replaced. All of the pipes must also be flushed.

Improper brake fluid, or mineral oil or water in the fluid, may cause the brake fluid to boil or cause deterioration of the rubber components. If the primary piston cups in the master cylinder are swollen, then the rubber parts have deteriorated. This deterioration may also be evidenced by swollen wheel cylinder piston seals on the drum brake wheels.

If rubber deterioration is evident, disassemble all the hydraulic parts and wash the parts with alcohol. Dry these parts with compressed air before reassembly to keep alcohol out of the system. Replace all the rubber parts in the system, including the hoses. Also, when working on the brake mechanisms, check for fluid on the linings. If excessive fluid is found, replace the linings.

If the master cylinder piston seals are in satisfactory condition, check for leaks or excessive heat conditions. If these conditions are not found, drain the fluid, flush the master cylinder with brake fluid, refill the master cylinder, and bleed the system. Refer to "Manual Bleeding the Brakes" in this section.

Brake Hose Inspection

The hydraulic brake hoses should be inspected at least twice a year. The brake hose assembly should be checked for road hazard damage, cracks, chafing of the outer cover, and for leaks or blisters. Inspect the hoses for proper routing and mounting. A brake hose that rubs on a suspension component will wear and eventually fail. A light and a mirror may be needed for an adequate inspection. If any of the above conditions are observed on the brake hose, adjust or replace the hose as necessary.

Warning Lamp Operation

This brake system uses a BRAKE warning lamp located in the instrument cluster. When the ignition switch is in the START position, the BRAKE warning lamp should glow and then go off when the ignition switch returns to the RUN position.

The following conditions will activate the BRAKE lamp:

Parking brake applied. The light should be on whenever the parking brake is applied and the ignition switch is ON.
Low fluid level. A low fluid level in the master cylinder will turn the BRAKE lamp on.
As a test of the lamp circuit. Vehicles with antilock brakes will illuminate the BRAKE lamp for 3 seconds when the ignition starter is turned ON.

Brake Lamp Warning Circuit Diagnosis

Test Description

The number(s) below refer to step(s) on the diagnostic table.

There are three possible symptoms of a problem: the brake warning lamp is always on; the brake warning lamp is never on; the brake warning lamp will not operate for a particular function. This test takes you to the appropriate starting point in the procedure.
This test checks whether the Antilock Brake System (ABS) system has turned on the brake warning lamp. If the vehicle is not equipped with ABS, the answer will be NO.
These steps test for simple conditions that can turn on the brake warning lamp.
This checks whether the brake fluid level switch is faulty.
This checks whether the parking brake switch is faulty.
This removes the circuit to the electronic brake control module (EBCM) in a vehicle with ABS.
This removes the parking brake switch circuit.
This removes the brake fluid level switch circuit.
This checks the only remaining circuitry that can activate the brake warning lamp.
This tests for the presence of battery voltage used by both the oil pressure lamp and the brake warning lamp.
This step begins a sequence that will restore voltage to the lamps.
This checks for a burned out indicator lamp.
This begins a sequence that will find the open that prevents contact to ground needed to operate the lamp.
This checks whether the ABS system has tried to turn on the brake warning lamp and could not. If the vehicle is not equipped with ABS, the answer is NO.
This step begins a search for a problem in the parking brake switch circuit.
This step begins a search for a problem in the brake fluid level switch circuit.

Brake Lamp Warning Circuit Diagnosis

Step	Action	Value(s)	Yes	No
1	Turn the ignition ON. Is the brake warning lamp always on?	-	Go to Step 2	Go to Step 19
2	Check the ABS warning lamp. Is the ABS warning lamp also on?	-	Go to Step 3	Go to Step 3
3	Use a scan tool to check for diagnostic trouble codes (DTCs) and follow the procedures for any DTCs found. Is the lamp still on?	-	Go to Step 4	System OK
4	Release the parking brake fully. Is the lamp off?	-	System OK	Go to Step 5
5	Check the brake fluid level. Is the fluid level acceptable?	-	Go to Step 7	Go to Step 6
6	Fill the brake fluid reservior with clean DOT-4 equivalent hydraulic fluid. Replace the cap on the brake fluid reservoir. Is the lamp stil on?	-	Go to Step 7	System OK
7	Unplug the harness connector from the brake fluid sensor switch. Is the lamp still on?	-	Go to Step 9	Go to Step 8
8	Replace the parking brake lever switch. Is the repair complete?	-	System OK	-
9	Reconnect the brake fluid level switch. Remove the rear console cover to expose the parking brake mechanism. Release the brake completely. Slide off the terminal with the BRN wire from the wiring harness. Does the lamp go out?	-	Go to Step 10	Go to Step 11
10	Replace the switch. Is the repair complete?	-	System OK	-
11	Replace the terminal back onto the switch. Is the vehicle equipped with ABS?	-	Go to Step 12	Go to Step 14
12	Unplug connector C207. Does the lamp go out?	-	Go to Step 13	Go to Step 14
13	Repair the short to ground in circuit BRN between terminal 1 of connector C207 and terminal 18 on the EBCM. Is the repair complete?	-	System OK	-
14	Disconnect connector C212. Is the lamp still on?	-	Go to Step 16	Go to Step 15
15	Repair the short to ground in circuit BRN between connector C212 and connector C207 or between connector C213 and the parking brake switch. Is the repair complete?	-	System OK	-
16	Disconnect connector C201. Does the lamp go out?	-	Go to Step 17	Go to Step 18
17	Repair the short to ground in circuit BRN between connector C201 and the brake fluid level switch. Is the repair complete?	-	System OK	-
18	Repair the short to ground in circuit BRN between terminal A5 of the instrument cluster and connector C201or connector C213. Is the repair complete?	-	System OK	-
19	Check the brake lamp after doing each of the following functions: Apply the parking brake. Remove the cap from the brake fluid reservoir. Command the lamp on using a scan tool. Does the brake warning lamp operate for any of these conditions?	-	Go to Step 32	Go to Step 20
20	Turn the ignition ON. Does the oil pressure indicator light?	-	Go to Step 24	Go to Step 21
21	Check fuse 3. Is the fuse in good condition?	-	Go to Step 23	Go to Step 22
22	Replace fuse 3 with another 10-amp fuse. Does the brake warning lamp function now?	-	System OK	-
23	Check Ef1 in the engine fuse block. Is Ef1 in good condition?	-	Go to step 25	Go to Step 24
24	Replace Ef1 with another 30-amp device. Is the repair complete?	-	System OK	-
25	Unplug C206 from the connection box behind the left-side kick panel. This is the largest connector at the bottom of the box. Use a digital volt meter (DVM) to measure voltage from terminal A5 of the cluster. Does the DVM indicate the specified voltage?	11-14 v	Go to Step 27	Go to Step 26
26	Repair the open in circuit PNK from terminal A5 in the connection box fuse 3 in the I/P fuse block. Is the repair complete?	-	System OK	-
27	Reconnect harness terminal A5 to the connection box. Gain access to the rear of the instrument cluster. Unplug the instrument 10-pin cluster connector. Use a DVM to measure the voltage from terminal B9 of the instrument cluster connector to ground. Does the DVM show the specified value?	11-14 v	Go to Step 28	Go to Step 29
28	Repair the open in circuit PNK between terminal B9 and A5 or from there in circuit BRN to terminal 18 of connector C201 Is the repair complete?	-	System OK	-
29	Remove the brake indicator lamp from its socket and examine it. Is the lamp burned out?	-	Go to Step 30	Go to Step 31
30	Replace the brake indicator lamp. Is the repair complete?	-	System OK	-
31	Return the brake indicator lamp to its socket the instrument cluster. Look for the open in circuit BRN between terminal A5 of the cluster and terminal 18 of connector C201. Repair any open found in circuit BRN. Is the repair complete?	-	System OK	-
32	Check the ABS lamp. Is the ABS lamp flashing?	-	Go to Step 33	Go to Step 34
33	Use a scan tool to determine what DTCs are present and repair them according to the tables for the DTCs involved. Is the repair complete?	-	System OK	-
34	Try applying the parking brake fully. Does the brake warning lamp fail to light when the parking brake is applied?	-	Go to Step 35	Go to Step 38
35	Expose the parking brake mechanism by removing the rear console. Use a jumper to short the terminal from the BRN wire to ground. Does the lamp come on?	-	Go to Step 36	Go to Step 37
36	Replace the parking brake switch or repair the grounding between the parking brake switch and the brake handle mounting or between the brake handle mounting and the vehicle body. Is the repair complete?	-	System OK	-
37	Repair the open in circuit BRN. This will be in one of two places: The I/P harness between terminal B9 of cluster and terminal 3 of connector C213. The floor harness between terminal 3 of connector C213 and the parking brake switch. Is the repair complete?	-	System OK	-
38	If the brake warning lamp is not indicating low brake fluid, remove the cap from the brake fluid reservoir to lift the sensor from the brake fluid. Does the lamp come on?	-	System OK	Go to Step 39
39	Unplug the harness connector from the sensor on the brake fluid reservoir cap. Use a jumper to short the terminals in the harness connector together. Does the lamp come on?	-	Go to Step 40	Go to Step 41
40	Install a new fluid level sensor switch into the brake fluid reservoir. Is the repair complete?	-	System OK	-
41	Use the jumper to short terminal 1 (BRN wire) to ground. Does the lamp come on?	-	Go to Step 42	Go to Step 43
42	Repair the open to ground in circuit BLK between the terminal 2 (BLK wire) of the harness connector for the level sensor switch and ground G102 at the left front corner of the vehicle. Is the repair complete?	-	System OK	-
43	Repair the open in circuit BRN. There are two possible locations for this open: The I/P harness between terminal B9 of cluster and terminal 18 of connector C201. The front harness between terminal 18 of connector C201and terminal 1 of the harness connector for the level sensor switch. Is the repair complete?	-	System OK	-

A low brake fluid level in the master cylinder will turn the BRAKE lamp ON. Refer to "Brake System Testing" in this section to test for fluid leaks.

MAINTENANCE AND REPAIR

ON-VEHICLE SERVICE

Manual Bleeding the Brakes

Important : Manual bleeding of the hydraulic modulator is not possible. If air enters the antilock brake hydraulic modulator, or if an unfilled modulator is installed, use the scan tool to bleed air out of the brake system. Replacement modulators are shipped already filled and bled. In normal on-vehicle service procedures involving the modulator, such as the procedure to replace the electronic brake control module, air will not enter the modulator. In such cases, use the bleeding procedure in this section.

Remove the booster reserve by applying the brakes several times with the engine OFF until all the reserve is depleted.

Important : If the master cylinder is known or suspected to have air in the bore, then it must be bled before any wheel cylinder or caliper is bled.

Fill the master cylinder reservoir with brake fluid. Keep the master cylinder at least one-half full of fluid during the bleeding operation.

Disconnect the front brake line(s) at the master cylinder.
Allow the brake fluid to fill the master cylinder until it begins to flow from the front pipe connector port.
Connect the front brake line(s) to the master cylinder.

Tighten

Tighten the brake lines to 16 N•m (12 lb-ft).

Slowly push and hold the brake pedal one time.

Loosen the front brake line at the master cylinder to purge all air from the cylinder.
Tighten the brake line as in Step 5, and then release the brake pedal slowly. Wait 15 seconds before proceeding to the next step.
Repeat the sequence, including the 15-second wait, until all the air is removed from the master cylinder bore.

Notice : Care must be taken to prevent brake fluid from contacting any painted surface to prevent damage to the paint finish.

After all the air has been removed at the forward connection(s), bleed the master cylinder at the rear (cowl) connection(s) in the same manner as with the front connections.

Attach a transparent tube over the valve. Allow the tube to hang submerged in brake fluid in a transparent container.

Slowly push and hold the brake pedal one time.
Remove the bleeder cap and loosen the bleeder screw to purge the air from the cylinder.
Tighten the bleeder screw.

Tighten

Tighten the bleeder screw to 9 N•m (80 lb-in).

Slowly release the brake pedal. Wait 15 seconds before proceeding with the next step.

Important : Rapid pumping of the brake pedal pushes the master cylinder secondary piston down the bore in a manner that makes it difficult to bleed the system.

Repeat the sequence, including the 15-second wait, until all the air is removed. It may be necessary to repeat the sequence 10 or more times to remove all the air.
Locate the front bleeder caps.

Proceed to bleed the front brakes following the appropriate sequence, beginning with Step 12.
Check the brake pedal for sponginess. Repeat the entire bleeding procedure to correct this condition.

Brake Hose - Rear -

Removal Procedure

Raise and suitably support the vehicle.
Disconnect the brake lines from the brake hoses at the body and the rear axle brackets.

Remove both brake hose E-ring retainers.
Remove the brake hoses from the brackets.

Installation Procedure

Install the brake hoses to the body and the rear axle brackets.
Connect the brake lines to the brake hose.

Tighten

Tighten the brake lines to 16 N•m (12 lb-ft).

Install the brake hose retainers.
Lower the vehicle.
Bleed the brake system. Refer to "Manual Bleeding the Brakes" in this section.
Check the brake system for leaks.

Brake Hose - Front -

Removal Procedure

Raise and suitably support the vehicle.
Disconnect the brake line from the brake hose support bracket on the wheel housing.
Remove the E-ring retainer.

Remove the brake hose from the wheel housing bracket.

Remove the bolt from the brake caliper.
Remove the seal rings and the brake hose.

Installation Procedure

Install the new brake hose to the caliper with new seal rings and the bolt.

Tighten

Tighten the front brake hose-to-caliper bolt to 40 N•m (30 lb-ft).

Install the brake hose and the E-ring retainer to the wheel housing bracket.
Connect the brake line to the brake hose.

Tighten

Tighten the brake line to 16 N•m (12 lb-ft).

Lower the vehicle.
Bleed the brake system. Refer to "Manual Bleeding the Brakes" in this section.
Check the brake system for leaks.

Stoplamp Switch

Removal Procedure

Disconnect the negative battery cable.
Remove the trim panel screws.
Remove the trim panel.

Turn the stoplamp switch and the connector assembly, and pull it from the brake pedal bracket.
Separate the stoplamp switch from the connector to replace the stoplamp switch.

Installation Procedure

Install the connector to the stoplamp switch.
Turn the stoplamp switch and the connector assembly, and twist it into the brake pedal bracket.

Press the brake pedal and pull the switch plunger to its maximum setting to adjust the switch.
Release the plunger and pull up on the pedal.
Install the trim panel screws.

Tighten

Tighten the trim panel screws to 7 N•m (62 lb-in).

Press the brake pedal and pull the switch plunger to its maximum setting to adjust the switch.

Brake Pedal

Removal Procedure

Remove the screws that hold the trim panel to the instrument panel.
Remove the trim panel.
Remove the stoplamp switch. Refer to "Stoplamp Switch" in this section.
Disconnect the retaining ring, the pin, and the spring from the pushrod/brake pedal connection.

Remove the pedal mounting shaft and nut.
Remove the brake pedal, exposing the brake booster pushrod and the pedal-to-dash panel bracket.

Remove the brake pedal cover.

Installation Procedure

Install a new brake pedal cover, if needed.
Coat the pedal shaft with grease.
Position the brake pedal on the pedal-to-dash panel bracket and the pedal shaft.
Place the nut on the pedal mounting shaft.

Tighten

Tighten the brake pedal-to-pedal bracket nut to 22 N•m (16 lb-ft.)

Install the pushrod to the pedal with the pin and the retaining ring.

Install the spring on the shaft in its original position.
Connect the stoplamp switch and the connector assembly by twisting it into the pedal bracket.

Install the trim panel with the screws.

Tighten

Tighten the trim panel screws to 7 N•m (62 lb-in).

GENERAL DESCRIPTION AND SYSTEM OPERATION

Hydraulic Fluid

Master cylinder fluid should meet the DOT-4 specification.

Use only clear fluid from a sealed container. Fluid that is exposed to the air will absorb moisture. Water in the master cylinder fluid will cause the fluid to boil and the rubber components to deteriorate.

Thoroughly clean the master cylinder reservoir cap before removing it. Do not let any dirt or foreign material fall into the fluid reservoir.

There is a fluid level switch in the master cylinder reservoir. When the fluid level is low, the BRAKE lamp in the instrument cluster will turn on. The correct master cylinder fluid level is marked on the left side of the master cylinder reservoir. If the fluid level is below the MIN indicator mark, check the hydraulic brake system for leaks, and then refill the reservoir to the MAX indicator mark.