this sounds worse then the resevoir being low... maybe you need a new master cylinder? or the lines may be tweeked somewhere... either way, this doesn't sound safe for you at all... take it back, drop it off, go to the general sales manager (bypass the service manager) and give him the keys, "fix this [email protected] thing or give me a new SAFE truck!" Safety is your biggest factor here, if you end up in a collision, it is their fault for being ignorant and not doing a thorough diagnostic and repair...