F/CMVSS Noncompliance - Brake Hydro-Boost Relief Valve Seal Fracture

THIS BULLETIN CANCELS AND REPLACES BULLETIN 04004, ISSUED JUNE 2004. THE INSPECTION PROCEDURE IN THIS BULLETIN HAS BEEN REVISED TO INCLUDE ADDITIONAL STAMPED NUMBERS ON THE HYDRAULIC BRAKE BOOSTER. ALL COPIES OF BULLETIN 04004 SHOULD BE DESTROYED.

General Motors has decided that certain 2003 and 2004 model year Cadillac Escalade, Escalade EXT and Escalade ESV; Chevrolet Silverado, Avalanche, Suburban, and Express; GMC Sierra, Yukon, Yukon XL, and Savana; HUMMER H2; and 2004 model year Chevrolet Tahoe vehicles fail to conform to either Federal/Canada Motor Vehicle Safety Standard 105, "Hydraulic and Electric Brake System", or Standard 135, "Light Vehicle Brake Systems". These vehicles may have a relief valve bore within the brake hydro-boost module that is not to specification. An out-of-specification bore could result in fracture of the relief valve o-ring seal within the module. If this happens, during brake applications the driver may be able to hear an engine compartment noise similar to the sound that occurs when the steering wheel is turned to a full stop position. The driver could also experience a slight increase in steering efforts while braking and parking. Under certain driving conditions, a fractured seal may require a slight increase in the applied brake pedal effort to achieve the same vehicle deceleration rate as prior to the seal fracture. If this were to occur, it could result in a vehicle crash without prior warning.

Dealers are to inspect the hydro-boost module and replace the relief valve, if necessary.

Involved are certain 2003 and 2004 model year Cadillac Escalade, Escalade EXT and Escalade ESV; Chevrolet Silverado, Avalanche, Suburban, and Express; GMC Sierra, Yukon, Yukon XL, and Savana; HUMMER H2 and 2004 model year Chevrolet Tahoe vehicles built within these VIN breakpoints:

Important: Dealers should confirm vehicle eligibility through GMVIS (GM Vehicle Inquiry System) before beginning recall repairs. [Not all vehicles within the above breakpoints may be involved.]

For US

For dealers with involved vehicles, a Campaign Initiation Detail Report containing the complete Vehicle Identification Number, customer name and address data has been prepared and will be loaded to the GM DealerWorld, Recall Information website. The customer name and address data furnished will enable dealers to follow up with customers involved in this program.

For Canada & IPC

Computer listings containing the complete Vehicle Identification Number, customer name and address data of involved vehicles have been prepared, and are being furnished to involved dealers. The customer name and address data will enable dealers to follow up with customers involved in this recall. Any dealer not receiving a computer listing with the recall bulletin has no involved vehicles currently assigned.

These dealer listings may contain customer names and addresses obtained from Motor Vehicle Registration Records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states/provinces/countries. Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this recall.

Parts required to complete this recall are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" before ordering parts. Normal orders should be placed on a DRO = Daily Replenishment Order. In an emergency situation, parts should be ordered on a CSO = Customer Special Order.

Important: It is estimated that only 20% of involved vehicles will require Valve Kit Repair. Please order parts accordingly.

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 and replacement relief valves.

2. Locate the relieve valve (2) on the hydraulic brake booster. The valve 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 no 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 bolt and nut (5). Also inspect for a paint mark (3) near the master cylinder outboard mounting bolt (5).

•	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 1 visible, then proceed to the next step.

•	If there are NO paint marks and there IS a stamped number OTHER THAN "1" (i.e. 0, 2, 3, 4, 5, etc.) visible, no further inspection or repairs are required.

•	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.

Notice: When repositioning the master cylinder in the next step, use care not to pinch, kink or damage the brake hoses or pipes.

Important: On fullsize 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.

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.

•	If a stamped number 1 is visible, then the relief valve must be replaced. Proceed to the next step.

•	If a stamped number OTHER THAN "1" (i.e. 0, 2, 3, 4, 5, etc.) 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 O-rings on the original valve for signs of damage. If an O-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 N·m (13 lb ft).

13. Using a clean shop towel, clean up any fluid that may have leaked out of they 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 the 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.

The General Motors Courtesy Transportation program is intended to minimize customer inconvenience when a vehicle requires a repair that is covered by the New Vehicle Limited Warranty. The availability of courtesy transportation to customers whose vehicles are within the warranty coverage period and involved in a product recall is very important in maintaining customer satisfaction. Dealers are to ensure that these customers understand that shuttle service or some other form of courtesy transportation is available and will be provided at no charge. Dealers should refer to the General Motors Service Policies and Procedures Manual for Courtesy Transportation guidelines.

Refer to the General Motors WINS Claim Processing Manual for details on Product Recall Claim Submission.

General Motors will notify customers of this recall on their vehicle (see copy of customer letter included with this bulletin).

Letters will be sent to known owners of record located within areas covered by the US National Traffic and Motor Vehicle Safety Act. For owners outside these areas, dealers should notify customers using the attached suggested dealer letter.

The US National Traffic and Motor Vehicle Safety Act provides that each vehicle that is subject to a recall of this type must be adequately repaired within a reasonable time after the customer has tendered it for repair. A failure to repair within sixty days after tender of a vehicle is prima facie evidence of failure to repair within a reasonable time. If the condition is not adequately repaired within a reasonable time, the customer may be entitled to an identical or reasonably equivalent vehicle at no charge or to a refund of the purchase price less a reasonable allowance for depreciation. To avoid having these burdensome remedies, every effort must be made to promptly schedule an appointment with each customer and to repair their vehicle as soon as possible. In the recall notification letters, customers are told how to contact the US National Highway Traffic Safety Administration if the recall is not completed within a reasonable time.

This bulletin is notice to you that the new motor vehicles included in this recall may not comply with the standard identified above. Under Title 49, Section 30112 of the United States Code, it is illegal for a dealer to sell a new motor vehicle which the dealer knows does not comply with an applicable Federal Motor Vehicle Safety Standard. As a consequence, if you sell any of these motor vehicles without first performing the recall correction, your dealership may be subject to a civil penalty for each such sale.

All unsold new vehicles in dealers' possession and subject to this recall MUST be held and inspected/repaired per the service procedure of this recall bulletin BEFORE customers take possession of these vehicles.

Dealers are to service all vehicles subject to this recall at no charge to customers, regardless of mileage, age of vehicle, or ownership, from this time forward.

Customers who have recently purchased vehicles sold from your vehicle inventory, and for which there is no customer information indicated on the dealer listing, are to be contacted by the dealer. Arrangements are to be made to make the required correction according to the instructions contained in this bulletin. This could be done by mailing to such customers a copy of the customer letter accompanying this bulletin. Recall follow-up cards should not be used for this purpose, since the customer may not as yet have received the notification letter.

In summary, whenever a vehicle subject to this recall enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the recall correction has been made before selling or releasing the vehicle.

Dear General Motors Customer:

This notice is sent to you in accordance with the requirements of the National Traffic and Motor Vehicle Safety Act. Federal regulation requires that any vehicle lessor receiving this recall notice must forward a copy of this notice to the lessee within ten days.

General Motors has decided that certain 2003 and 2004 model year Cadillac Escalade, Escalade EXT and Escalade ESV; Chevrolet Silverado, Avalanche, Suburban, and Express; GMC Sierra, Yukon, Yukon XL, and Savana; HUMMER H2; and 2004 model year Chevrolet Tahoe vehicles fail to conform to either Federal/Canada Motor Vehicle Safety Standard 105, "Hydraulic and Electric Brake System", or Standard 135, "Light Vehicle Brake Systems". These vehicles may have a relief valve bore within the brake hydro-boost module that is not to specification. An out-of-specification bore could result in fracture of the relief valve o-ring seal within the module. If this happens, during brake applications the driver may be able to hear an engine compartment noise similar to the sound that occurs when the steering wheel is turned to a full stop position. The driver could also experience a slight increase in steering efforts while braking and parking. Under certain driving conditions, a fractured seal may require a slight increase in the applied brake pedal effort to achieve the same vehicle deceleration rate as prior to the seal fracture. If this were to occur, it could result in a vehicle crash without prior warning.

Your GM dealer will inspect the hydro-boost module, and replace the relief valve if necessary. This service will be performed for you at no charge .

This inspection and correction, if necessary, will take approximately 20 to 25 minutes. However, due to scheduling requirements, your dealer may need your vehicle for a longer period of time.

To limit any possible inconvenience, we recommend that you contact your GM dealer as soon as possible to schedule an appointment for this repair. By scheduling an appointment, your dealer can ensure that the necessary parts will be available on your scheduled appointment date. Should your dealer be unable to schedule a service date within a reasonable time, you should contact the appropriate Customer Assistance Center at the number listed below. The Customer Assistance Center hours of operation are from 8:00 AM - 11:00 PM eastern standard time Monday through Friday

If, after contacting the appropriate customer assistance center, you are still not satisfied that we have done our best to remedy this condition without charge and within a reasonable time, you may wish to write the Administrator, National Highway Traffic Safety Administration, 400 Seventh Street SW, Washington, DC 20590 or call 1-888-327-4236.

The enclosed customer reply form identifies your vehicles. Presentation of this form to your dealer will assist in making the necessary correction in the shortest possible time. If you no longer own this vehicle, please let us know by completing the form and mailing it back to us.

If your vehicle is within the New Vehicle Limited Warranty your dealer will provide you with shuttle service or some other form of courtesy transportation while your vehicle is at the dealership for this repair. Please refer to your Owner's Manual and your dealer for details on Courtesy Transportation.

More information about this recall (including answers to frequently asked questions) is available online at the Owner Center at My GMLink. This free online service offers vehicle and ownership related information and tools tailored to your specific vehicle. To join, visit www.mygmlink.com , and enter your vehicle's 17-character vehicle identification number (VIN) shown on the enclosed form to get the most personalized information for your vehicle.

We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your safety and continued satisfaction with our products.

General Motors Corporation

Enclosure

04004