I’m pretty sure I’ve seen a post about this but I can’t find it so I apologize for the duplicate. I flushed my coolant system today. Drained about 4 gallons, the truck holds 4.25 gallons of coolant so I got about as much as I could out without removing any hoses. Ran some water through it for a few minutes and closed the drain port. Filled the system up with water and the flush chemical. Ran the truck for about 10 minutes and made sure the thermostat was open (top radiator hose was hot). Then drained the system again but I didn’t catch it in a bucket so I’m not sure how much drained out. Flushed the system again for a few minutes until the water ran clear and stopped and closed the drain port. Heres my issue, I started to fill the system back up with coolant but only got 1 gallon back in the system. So I turned the truck on and let it run until the thermostat opened but the coolant level did not drop at all. I drove around a few miles with the heat blasting and the engine never got hot. So either the majority of the water did not drain or something else. Anyone else experienced this? Any thoughts?