Tubeless setup question, leak before put in sealant

I'm setting up tubeless myself by following some youtube videos. I've managed clean and taped the rim. pump up the tire without put in sealant just to test out. I can put the tire to around 50 psi and keep it for 1 hour or so. but then the air all leaked out after 2 hours. Is this normal without sealant? If sealant can seal out all the small leaks? or should I check the valve and tapes?