Q: Filled up this morning, after driving about 20 miles in the heat, strong gas smell inside and outside of the van. No visible leaks

Be careful of using some fuel additives. From my experience I’ve found some additives that will cause the fuel to boil in the heat. Also, depending on where you got your fuel, you may have got a "winter blend" of fuel which can be more volatile than a summer blend. These fuels ignite better in winter but will be too volatile in the summer. The sound you may be hearing could be winter fuel boiling when it gets hot. Your fuel may have a strong gas smell when you fill up on gas and you have your door or window open as fumes can get into your car or van. However, I would also check and make sure your fuel vapor valve is not leaking.

I recommend getting the vehicle looked at by a qualified technician. They will be able to diagnose the smell you’re experiencing and make the necessary repairs.