Can I return a used Vehichle I just bought because its a lemon?

Last week I bought a used truck well the check gauge light comes on and the gauges spike and it started smoking so I had to pull over and I call the dealer and told them. I had it towed to a Mechanic who said it needed a sealant and freeze plug. So they fixed and the used car dealer payed part of it. Well we bring it home tonight and its still doing the same thing. Can I take it back and null and void everything? Or am I basically screwed