GM Service Manual Online
For 1990-2009 cars only

Vacuum Booster Diagnosis Brakes Grab

Step

Action

Value(s)

Yes

No

DEFINITION: The brakes grab on and off.

1

Inspect the hydraulic brake pipes and hoses.

Are the hydraulic brake pipes and hoses damaged?

--

Go to Step 2

Go to Step 3

2

Replace the hydraulic brake pipes and hoses as necessary. Refer to:

    •  Brake Pipe Replacement

Do the brakes still grab?

--

Go to Step 3

System OK

3

Inspect the fluid level in the master cylinder.

Is the fluid level low in the master cylinder?

--

Go to Step 4

Go to Step 5

4

Fill the reservoirs with the proper brake fluid. Check for leaks.

Do the brakes still grab?

--

Go to Step 5

System OK

5

Inspect the master cylinder seals.

Are the master cylinder seals faulty?

--

Go to Step 6

Go to Step 7

6

Repair or replace the master cylinder seals as necessary. Refer to Master Cylinder Overhaul .

Do the brakes still grab?

--

Go to Step 7

System OK

7

Inspect the master cylinder casing.

Is the master cylinder casing cracked?

--

Go to Step 8

Go to Step 9

8

Replace the master cylinder. Refer to Master Cylinder Replacement .

Do the brakes still grab?

--

Go to Step 9

System OK

9

Look for leaks in the following components:

    • Front calipers
    • Rear wheel cylinders
    • Pipes
    • Connections

Do any of the components leak?

--

Go to Step 10

Go to Step 11

10

Inspect and repair the leaking components as necessary.

Do the brakes still grab?

--

Go to Step 11

System OK

11

Inspect for air in the hydraulic system.

Is there air in the hydraulic system?

--

Go to Step 12

Go to Hydraulic Brake Diagnostic System Check

12

Bleed the hydraulic system. Refer to Hydraulic Brake System Bleeding .

Do the brakes still grab?

--

Go to Hydraulic Brake Diagnostic System Check

System OK