Coolant loss. possible bad radiator cap?
 

I have a 2017 Hyundai Accent with about 104k miles. I decided now that the warranty is up I'd be doing my own servicing to the engine as opposed to taking it somewhere. So while checking the oil I figured id check the coolant level. My overflow was sitting at the low level. I know the last time it was filled was last year.
The car doesn't overheat or have any signs of coolant leaks. But when taking the radiator cap off i noticed there was some white buildup around the seal on the rad cap and the filler neck seal. I checked after the car was off for about 15-20 minutes and there didn't seem to be any pressure behind the cap. So the engine was still kinda warm just not operating temp.

Im leaning towards a bad radiator cap but I thought id check with yall first.

If you would describe the material as "soupy" , I would suggest you have a qualified shop check out your vehicle. Grey soupy material in the coolant could be an indication of oil getting into the cooling system.

The coolant looks good. No signs of head gasket failure. I cleaned the white crud from around the seal on the cap and filler neck. I topped off the coolant as well. When i checked yesterday it did have a little bit of pressure that was released when I loosened the cap. Im going to drive it and check the coolant again this week to see if there is any drastic change in the level.