| • | Inspect the CNG fuel tank and brackets every three years or 60 000 km (36,000 mi), whichever comes first. Record the inspection information in the CNG Fuel Tank Inspection Record. The CNG Fuel Tank Inspection Record is located in the owner's manual supplement. |
| • | Do not remove the tank from the vehicle for general inspections. |
| • | However, if the tank has been exposed to corrosive chemicals such as acid or alkali, remove the tank in order to perform a complete inspection. |
| • | If the tank is replaced, perform the following steps: |
| 1. | Obtain a new CNG Fuel Only label. |
| 2. | Obtain a new Bi-fuel Information label. |
| 3. | Record the new tank service expiration date -- the date of the manufacturer plus 15 years -- on both labels. |
Tank Label Inspection Procedure
Verify that the CNG fuel tank label is in place.
Contact the GM Technical Assistance Center (TAC) if any of the following conditions exist:
| • | The label is not readable. |
Verify that the tank expiration date matches on the tank, the fill door and the underhood label. If needed, replace the fill door and the underhood label so the expiration date matches the tank label.
Tank Wrap Inspection Procedure
Important: Cracking or splitting of the carbon fiber wrap around the circumference of the tank may occur during manufacture. This is normal. It does not affect tank strength and does not require repair.
A carbon fiber epoxy matrix hoop wrap protects the CNG fuel tank. Inspect and resurface abrasions or cuts as follows:
Level 1 Abrasions:
| • | Level 1 abrasions are minor abrasions such as scuffs that are less than 0.25 mm (0.010 in) deep. |
| • | It is not necessary to resurface Level 1 abrasions. |
Level 2 Abrasions:
| | Important: Replace tanks with abrasions that exceed Level 2 specifications.
|
| • | Level 2 abrasions are abrasions with some exposed fibers or flat spots with a depth between 0.25-0.76 mm (0.010-0.030 in). |
| • | Resurface Level 2 abrasions before returning the tank to service. |
| | Important: Cut away frayed fibers before application of the epoxy coating.
|
| • | Resin coat the abrasion with any commercial room temperature cure two-component epoxy resin -- Loctite® Part No. 14600 or equivalent. |
Level 1 Cuts:
| • | Level 1 cuts are cuts or scratches that are less than 0.50 mm (0.020 in) deep. |
| • | Level 1 cuts may be any length. |
| • | Level 1 cuts may be in any direction. |
| • | It is not necessary to resurface Level 1 cuts. |
Level 2 Cuts:
| | Important: Repair Level 2 cuts before returning the tank to service.
|
| • | Level 2 cuts are cuts or scratches that are up to 0.76 mm (0.030 in) deep. |
| • | Level 2 cuts are up to 203 mm (8.0 in) long. |
| • | Resurface Level 2 cuts before returning the tank to service. |
| | Important: Cut away frayed fibers before applying the epoxy coating.
|
| • | Resin coat the cut with any commercial room temperature cure two-component epoxy resin -- Loctite® Part No. 14600 or equivalent. |
Metal Tank End Inspection Procedure
A multi-coat paint system with a zinc-rich primer protects the metal tank. Inspect and recoat chips in the paint as follows:
Level 1 Chips:
| • | Level 1 chips are chips or abrasions in the coating that do not penetrate the black top coat. |
| • | Level 1 chips do not expose the gray zinc-rich primer. |
| • | Level 1 chips do not require resurfacing. |
Level 2 Chips:
| • | Level 2 chips are chips or abrasions that penetrate the black top coat. |
| • | Recoat Level 2 chips or abrasions in order to prevent corrosion |
| • | The following two repair methods are recommended depending on whether the zinc-rich primer is still intact: |
Method 1:
| - | Recoat the chip using any commercial room temperature cure two-component epoxy resin -- Loctite® Part No. 14600 or equivalent -- if the chip has not penetrated the zinc-rich primer. |
| - | This is the same material used to repair Level 2 tank wrap damage. |
| • | The following procedure is recommended if the chip has penetrated the zinc-rich primer and exposed the bare metal: |
Method 2:
| - | Sand the damaged area in order to remove any rust and to rough-up the surrounding coating. |
| - | Clean the damaged area with a commercial prepaint cleaning solvent -- Dupont® Prep Sol or equivalent. |
| - | Apply a zinc-rich cold galvanizing primer -- LPS® Part No. 00516 or equivalent. |
| - | Coat the area after the primer has cured using a room temperature cure two-component epoxy resin -- Loctite® Part No. 14600 or equivalent. |
Dents
Important: Replace tanks with dents to the metal edges greater than 1.52 mm (0.060 in) deep.
Gouges
Important: Replace tanks with sharp gouges penetrating the paint and the metal.
Mounting Bracket Inspection Procedure
- Verify that the rubber isolator is properly seated on the tank brackets and straps.
- Inspect the rubber isolator for cracks, deterioration or other damage.
- Replace the rubber isolator if necessary.
- Inspect the tank brackets, straps, mounting frame and mounding hardware for cracks, corrosion, deformation or other damage.
- Replace if necessary.
Removing From Service
| • | The CNG fuel tank has a fifteen year service life from the date of manufacture. |
| • | The CNG tank manufacture date appears on a label on the tank. |
| • | The tank expiration date is on the CNG Fuel Only label and the Bi-fuel Information label. |
| • | Any tank in service for fifteen years or more must be removed from service using the following procedure: |
| 4. | Place the tank outside in a well ventilated area. |
| 5. | Allow the tank to stand for 24 hours with the HPL removed. |
| 6. | Drill a 0.64 cm (¼ in) hole after the last digit of the tank identification number stamped into the valve end of the tank. |
| 7. | Dispose of the tank in a safe and approved manner. |
