My car is leaking a little water from under the 2.7L VA cover by the thermostat and losing coolant from the reservoir

Have cover removed and seal with sealer and new gasket.

I think you meant 5.7L V8? Remove the plastic cover and see if you can pin point the leak. I'm guessing it's leaking from the thermostat housing? If so, just replace with new thermostat and gasket. If you're losing fluid from the reserve jug from a leak, you will have to remove jug and look for a crack in the bottom.

I have change the radiator and the water pump the threomast and the water tank and still my car is heating up and the water from the water tank is still bubble and spilling out ,... i went to another mechanic he said that the water tank is no good that was used so i need to change it again because is not giving no pressure on being close pls help someone

Guru59HR, you may have a bad head gasket. Go to the auto store and purchase a block tester kit. Here is a short video on how to use one. https://www.youtube.com/watch?v=YY2w2QvwAVo&t=90s