1994 Toyota Pickup WHITE SMOKE

Last year I had a complete overhaul done (september) ran great in june of this year had fuel leak from fuel damper on back of engine by firewall which mechanic had to take entire intake off to access it, fixed. Now the problem, 2 weeks after that temperatue rising on guage, coolant low, white smoke at start up, pulled the truck to mechanic sat about 2 weeks before he could get to it when he did every thing was fine no smoke no coolant loss no coolant in oil he ran it 2 weeks from his shop, let it idle for 3 hours every thing fine. Changed radiator cap as a possibility and oil. I drove it for a week ran great but last night coolant spewed out of radiator resovior, white smoke, had to add a jug of coolant to radiator, slight missing, a real mystery, would do none of this with mechanic, I am taking it back to him this week any thoughts or suggestions to do, that I can pass on to him. Thanks