Vannin' Home Forums Chevy General Discussion Condensation under floor mat above fuel tank

Hello, I have a unique situation. In the back of the van (1990 GMC Rally STX) the floor mat above the fuel tank keeps getting damp. It's only slightly damp and I've had the entire floor mat out and dried it completely, put it back it, and after a couple of drives it wet again. No rain to speak of and the van is parked in a garage.

Anyone else ever seen this in their van?

Does it have a rear heater ?

Or a leaky condensation drain from a rear air unit above the back doors?

Has a rear heater but that's not leaking. No rear A/C unit

Check the temp of the floor the next time you drive it, is the area warm? Hot fuel returning from the engine warming up tank attracting moisture, tank cools condenses moisture? Exhaust leak around tank heating floor same thing? How is the humidity by you?

I'll check the temp of the floor the next time I drive it and also look for any exhaust leaks too. I'll report back what I find.

The 70s tanks aren’t welded in place. I’ve removed mine (79 G30) before and it is just held on b the tank straps. I have no info on if a swap is possible though.