You will need to have the tank replaced. It is not repairable. GM has recognized this problem and has extended the warranty coverage for this defect for 10 years or 150,000 miles. If you have less than 150,000 miles on your Rendezvous, you should be covered.
Here is a copy of the special policy.
# XXXXX: Special Coverage Adjustment - Fuel Tank Inlet Check Valve (ICV) Fracture - (Aug 8, 2008)
07203C -- SPECIAL COVERAGE ADJUSTMENT - FUEL TANK INLET CHECK VALVE (ICV) FRACTURE - (AUG 8, 2008)
2002-2004 BUICK RENDEZVOUS
2001-2004 CHEVROLET VENTURE (REGULAR WHEELBASE)
2001-2004 PONTIAC AZTEK, MONTANA (REGULAR WHEELBASE)
The Parts Information section in this bulletin has been revised. The correct gasket part number for the 2001-2003 Pontiac Aztek and the 2002-2003 Buick Rendezvous is 22681652. Discard all copies of bulletin 07203B, issued July 2008.
Some customers of 2002-2004 model year Buick Rendezvous; 2001-2004 model year Chevrolet Venture (regular wheelbase); and Pontiac Aztek and Montana (regular wheelbase) vehicles may comment about strong fuel odor or droplets of fuel on the ground during refueling or normal driving. This may be caused by a small crack at the base of the fill tube near the fuel tank.
Special Policy Adjustment
This special coverage covers the condition described above for a period of 10 years or 150,000 miles (240,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the customer.
For vehicles covered by Vehicle Service Contracts, all eligible claims with repair orders on or after January 24, 2008, are covered by this special coverage and must be submitted using the labor operation codes provided with this bulletin. Claims with repair orders prior to January 24, 2008, must be submitted to the Service Contract provider.