Service Procedure
The following procedure provides instructions for inspecting, and if necessary, replacing the hydraulic brake booster relief valve.1. Open the hood.
Important
You may notice that there is a blue epoxy-type material in the center of the relief valve described in the next step. This material will be found in both the original arid replacement relief valves.
2. Locate the relief valve (2) on the hydraulic brake booster. The valve is located in the front of the brake booster directly behind the master cylinder reservoir (1).
^ If the color of the relief valve is metallic yellow or has a brass appearance, then further action is required.
^ If the color of the relief valve is silver or aluminum, continue to the next step.
Important
If present, the stamped number being described in the next step would be on the mounting surface for the master cylinder on the hydraulic brake booster. The number may be difficult to see if there is any corrosion on the unpainted surface. As a result, it may be necessary to clean the surface with a piece of emery or sandpaper.
3. Inspect the hydraulic brake booster at the location shown (4) for a stamped number. The location (4) is the same surface that the master cylinder mounts on, just above the outboard mounting bolt and nut (5). Also inspect for a paint mark (3) near the master cylinder outboard mounting bolt (5). If a stamped number is found it will be a 1, 2, 3, or 4. If a paint mark is found, it will be yellow, pink, or white.
^ If a yellow, pink, or white paint mark IS visible, no further inspection or repairs are required. Disregard any stamped number found when a yellow, pink, or white paint mark is visible.
^ If there are NO paint marks and there IS a stamped number 2, 3, or 4 visible, no further inspection or repairs are required.
^ If there are NO paint marks and there IS a stamped number 1 visible, then proceed to the next step.
^ If there are NO paint marks and there are NO stamped numbers visible, then proceed to the next step.
Caution
Care should be taken when working around the accumulator since it contains high-pressure compressed gas and hydraulic fluid.
4. With the ignition in the OFF position, pump the brake pedal a minimum of ten times.
5. On van models, remove the two bolts that attach the diagonal brace between the left front fender and radiator support. Remove the brace and the water deflector that is attached to it.
6. On all models, remove the two nuts that attach the master cylinder to the hydraulic brake booster. A 13 mm wrench installed on the bolt head may be required to prevent the bolt from spinning.
Important
On full size pickups and utilities, the bracket that attaches the brake combination valve will need to be removed from the mounting bolts at the same time that the master cylinder is removed and repositioned in the next step.
Notice
When repositioning the master cylinder in the next step, use care not to pinch, kink, or damage the brake hoses or pipes.
7. Remove and reposition the master cylinder away from the hydraulic brake booster so that the machined surface on the front of the booster where the master cylinder was mounted is visible.
8. Inspect the machined surface that was covered by the master cylinder on the front of the hydraulic brake booster at the location (1) shown for a stamped number. The stamped number will be a number 1, 2, 3, or 4.
^ If a stamped number 1 is visible, then the relief valve must be replaced. Proceed to the next step.
^ If a stamped number 2, 3, or 4 is visible, then no further action is required. Proceed to Step 14 and reinstall the master cylinder.
^ If no stamped number is visible, then no further action is required. Proceed to Step 14 and reinstall the master cylinder.
9. Cover the master cylinder with a clean shop towel in order to protect it from fluids or cleaners. Also, place a shop towel under the hydraulic brake booster to absorb any fluid that may leak out of the unit when the relief valve is removed in the next step.
10. Using the tool (2) included with the new relief valve, unscrew the original relief valve (1) from the hydraulic brake booster.
Notice
DO NOT blow compressed air into the bore or use any commercially available cleaners to flush the valve bore in the next step. This could damage the booster or master cylinder.
11. Inspect the two 0-rings on the original valve for signs of damage. If an 0-ring is missing, broken, or damaged, inspect the bore in the hydraulic brake booster for any pieces or debris using a non-metallic type tool or a clean "lint-free" towel.
Important
A torque wrench must be used when tightening the valve in the next step. In addition, a 3/8 inch drive to 1/4 inch drive adapter will be needed if your torque wrench is a 3/8 inch drive.
Important
After tightening the NEW relief valve in the next step, a small gap may exist between the head on the valve and the hydraulic brake booster. This condition is normal.
12. Insert the NEW relief valve into the bore.
Tighten
Tighten to 17 Nm (13 lb ft).
13. Using a clean shop towel, clean up any fluid that may have leaked out of the hydraulic brake booster when removing the original valve.
14. Position the master cylinder (and brake combination valve mounting bracket on full size pickups and utilities) on the mounting bolts on the hydraulic brake booster.
15. With the master cylinder mounted flush to the booster, install the nuts.
Tighten
Tighten the nuts to 33 N.m (24 lb ft).
16. On van models, install the diagonal brace with the water deflector attached to it between the left fender and the radiator. Install the two bolts.
Tighten
Tighten bolts to 25 N.m (18 lb ft).
17. Start the engine and verify the hydraulic brake booster operation.
18. Turn the engine OFF and check the power steering fluid reservoir. Add fluid if necessary.
19. Close the hood.