So I've been fighting coolant problems on my truck for a while. There's coolant on the garage floor directly below the motor. Water pump was replaced 25k miles ago, pressure test did not expose any leaks, no visible signs of leakage, but low coolant light comes on after the truck has been running a while and sitting still. After a 30 mile highway drive, I let it sit in the driveway idling for a half hour and no drips. When hot, the truck has about an inch of coolant in the tank. No over heating at all. Any ideas? I also have very light white smoke coming out my tail pipes even on hot days which suggests its burning coolant but doesn't explain the puddles on the floor.