Buying a car online in bitcoin, you will need to declare where the money comes from. Also, you will need to make an inspection to ensure the vehicle its worth to buy.
What happen if you are not satisfied with the purchase, you can't make a chargeback!
Buying a car online seems to very risky on my part and as you said we should really look up or check the car first before you tend to buy because we could not really make chargebacks and you will surely regret on your purchase but if you are buying a brand new car then there would be no problem at all.
Even in case of brand new car, shipping may be a problem too, if you are not in the same country. Things such as Cars, homes should be seen first and then bought on spot, rather than online. These things are not suited to buy online as they can cause problems once you physically receive them without checking live before.