Easy. If the headliner is water stained insist the replace it. I can't imagine too much water intruding via the lamp so I wouldn't worry about corrosion anywhere else, once they pull the headliner they'll see.

 

Took mine in for the same prob,they replaced the 3rd brake light, the headliner and fully detail inside. Mine is tuned with catless longtubes,and a few other things, no probs yet with them. They just don't like when it has a lift on it and you bring it for CV joints lol, but still replaced them.

 

Well they just replaced the light and the gasket and let it dry. The headliner didnt get stained. They also told me the warranty does'nt cover water damage.

 

Thats bull the warranty does cover water damage since it was a defective part that caused it. My 07 NBS crew has a fact sun roof. I took it back 4 times before the leak was found. At first they thought it was the brake light but with a GM engineer,[actually called me at home], they found a defect at the factory that wasn`t cleaning out the drains from the sun roof. The last time I was told that if they couldn`t repair the leak that after 4 attempts they would replace the vehicle they cleaned/detailed the complete truck and took good care of me also.

 

the warranty will cover water damage if it was a factory defect that caused the damage.

 

If it's a New truck they should make it as new again If under warranty!

Those dumb ****'s should put a guy in side the cab and hit the truck with a pressure washer to find the damn Leak :~( freaking loosers LOL