Sudden hard brake pedal

Tiny
DFRANCA
  • MEMBER
  • 2009 CHEVROLET COBALT
  • 2.0L
  • 4 CYL
  • TURBO
  • 2WD
  • 115,000 MILES
Today I was driving on the highway to work and came up on some traffic and pressed my brake pedal. The pedal was very hard and vibrated. Then I took my foot off the pedal and pressed it again and it was fine. It was not a sudden hard stop where ABS should have kicked on. Also the past year the brake pedal takes a decent amount of pressure to apply stopping power.
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Thursday, July 18th, 2019 AT 6:45 AM

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Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome to 2CarPros.

If it vibrated and was difficult to press, it does sound like the ABS was actuated even though you weren't skidding. That can very possibly happen if one of the wheel speed sensors is going bad. That is where I would start checking. However, if it is an intermittent issue, it could test good when you check it.

Regardless, here are the directions for testing an ABS wheel speed sensor:

https://www.2carpros.com/articles/abs-wheel-speed-sensor-test

If you find one to be bad, here is a link that shows in general how one is replaced:

https://www.2carpros.com/articles/how-to-replace-an-abs-wheel-speed-sensor

Here are links that explain how to use a volt / multi meter and check wiring:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-check-wiring

_________________

If you look at pic 1, it shows sensor locations for your vehicle. Start by making sure nothing is loose, disconnect the sensor connector and inspect it for corrosion or damage and so on.
If it is determined that one is bad, here are the specific directions for your vehicle to replace them. The attached pics correlate with the directions.

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Front:

REMOVAL AND REPLACEMENT
Front Wheel Speed Sensor Replacement

Removal Procedure

1. Remove the left front wheel. Refer to Tire and Wheel Removal and Installation (See: Wheels and Tires > Removal and Replacement).

pic 2

2. Disconnect the vehicle speed sensor (VSS) electrical connector (2).

pic 3

3. Remove the retainer bolt.
4. Remove the retainer.
5. Remove the VSS.
6. Remove and discard the O-ring.

Installation Procedure

1. Lubricate a new O-ring with transmission fluid. Refer to Lubrication Specifications (See: Manual Transmission/Transaxle > Fluid Types).
2. Install the new O-ring.

pic 4

3. Install the VSS assembly.

Caution: Refer to Fastener Caution (See: Vehicle > Vehicle Damage Warnings > Fastener Caution).

4. Install the VSS retainer bolt.

Tighten the bolt to 9 Nm (80 lb in).

pic 5

5. Connect the VSS connector to the VSS (2).
6. Install the left front wheel. Refer to Tire and Wheel Removal and Installation (See: Wheels and Tires > Removal and Replacement).

______________________________

Now if you find that one of the rear sensors has failed, the hub and sensor are one part and it is a bit move involved to replace. Here are those directions and the remaining pics correlate with the directions. Note that I have added both procedures for if the vehicle has rear disc brakes or rear drum brakes. If you look at the pics, you will be able to identify which you have. However, since it is a turbo, I suspect they are disc.

____________________________

REAR WHEEL BEARING AND HUB REPLACEMENT (DISC BRAKE)
Rear Wheel Bearing and Hub Replacement (Disc Brake)

Removal Procedure

1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle (See: Vehicle Lifting > Procedures > Lifting and Jacking the Vehicle).
2. Remove the tire and wheel assembly. Refer to Tire and Wheel Removal and Installation (See: Wheels and Tires > Removal and Replacement).
3. Without disconnecting the hydraulic brake flex hose, remove and support the rear brake caliper and bracket as an assembly, and remove the rear brake rotor. Refer to Rear Brake Rotor Replacement (See: Brake Rotor/Disc > Removal and Replacement).
4. Disconnect the electrical connector from the wheel speed sensor.

pic 6

5. Remove the wheel bearing/hub assembly mounting nuts.
6. Remove the wheel bearing/hub assembly and the disc brake backing plate from the rear axle assembly.

Installation Procedure

pic 7

1. Install the wheel bearing/hub assembly and the brake backing plate to the rear axle assembly.

Caution: Refer to Fastener Caution (See: Vehicle > Vehicle Damage Warnings > Fastener Caution).

2. Install the wheel bearing/hub assembly mounting nuts to the axle assembly. Tighten the nuts evenly, in a cross-pattern.

Tighten the nuts to 45 Nm (33 lb ft) plus 30 degrees.

3. Connect the electrical connector to the wheel speed sensor.
4. Install the brake rotor, and install the brake caliper and bracket as an assembly. Refer to Rear Brake Rotor Replacement (See: Brake Rotor/Disc > Removal and Replacement).
5. Install the tire and wheel assembly. Refer to Tire and Wheel Removal and Installation (See: Wheels and Tires > Removal and Replacement).
6. Lower the vehicle.

____________________________

Rear drum brakes.

REAR WHEEL BEARING AND HUB REPLACEMENT (DRUM BRAKE)
Rear Wheel Bearing and Hub Replacement (Drum Brake)

Removal Procedure

1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle (See: Vehicle Lifting > Procedures > Lifting and Jacking the Vehicle).
2. Remove the tire and wheel assembly. Refer to Tire and Wheel Removal and Installation (See: Wheels and Tires > Removal and Replacement).
3. Remove the brake drum. Refer to Brake Drum Replacement (See: Brake Drum > Removal and Replacement).

pic 8

4. Remove the plug from the drum brake actuator access hole in the backing plate. Using the access hole, install a support (1) for the brake backing plate.
5. Disconnect the electrical connector (2) from the wheel speed sensor, if equipped with ABS.
6. Remove the wheel bearing/hub assembly mounting nuts (3).

pic 9

7. Remove the wheel bearing/hub assembly from the rear axle assembly and brake backing plate.

Installation Procedure

pic 10

1. Install the wheel bearing/hub assembly to the brake backing plate and the rear axle assembly.

pic11

Caution: Refer to Fastener Caution (See: Vehicle > Vehicle Damage Warnings > Fastener Caution).

2. Install the wheel bearing/hub assembly mounting nuts (3) to the axle assembly. Tighten the nuts evenly, in a cross-pattern.

Tighten the nuts to 45 Nm (33 lb ft) plus 30 degrees.

3. Connect the electrical connector (2) to the wheel speed sensor, if equipped with ABS.
4. Remove the support (1) from the brake backing plate.
5. Install the plug to the drum brake actuator access hole in the backing plate.
6. Install the brake drum. Refer to Brake Drum Replacement (See: Brake Drum > Removal and Replacement).
7. Install the tire and wheel assembly. Refer to Tire and Wheel Removal and Installation (See: Wheels and Tires > Removal and Replacement).
8. Lower the vehicle.

_______________________________

Please feel free to let me know if you need help or have other questions.

Take care,
Joe
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Thursday, July 18th, 2019 AT 7:43 PM

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