White smoke on start up

Engine problem

I have been having problems with my car blowing white smoke when it first starts up. I have taken it to the mechanic and they have told me that there was on oil leak in the timing cover and necessary to install new sealant and gasket. That work was done! But the smoke did not stop 2 months later I took it again now they said the found problems with the tensioners, and valve seals leaking. I just got my car back yesterday, when I turned my car on this morning the big white cloud of smoke is still there! I don't know what else to do. What could be there problem and should I go to another mechanic?