White smoke appears after i changed the valvecover gasket thermostat and radiator

Steam from antifreeze leak . May be radiator, radiator or heater hoses, thermostat gasket, intake gaskets, etc. . A pressure tester can be used with enginecold to detect leakage area.

Hi,
White smoke usually indicates there is a problem with the cooling system to the engine. Here are some things I would check.
Coolant
Radiator
Thermostat
Hose from radiator to thermostat
Most importantly, the valve cover gasket. When you replace this type of gasket, we need to make sure you torque down the bolts in a certain pattern at a certain torque.

I hope this helps.

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Blows out? Probably a head gasket. they don't always blow white smoke. Parts store sell a kit to check exhaust in the reservoir or radiator. Best bet. If it blows out, Fill it with water, leave the cap off. Start it and put your hand over the reservoir opening. You feel any pressure being cold. Head gasket.

When you say "sometimes", whad do you mean exactly? When cold? When warm? When accellerating?
White exhaust smoke (which has a sweet smell) is often an indication of a blown head gasket. You'll need a compression test or test the antifreeze against exhaust gas contamination. Although the compression test will tell you more about the contition of the head gasket.
Where exactly does the white smoke come from under the hood? Maybe there's a puncture somewhere on the radiator hose or heater hose and the antifreeze sprays on the exhaust? Please check. There still is a tiny bit of hope it's not the gasket...

Water pump may be bad,

If i remember right the color of the smoke will tell you what it is and i think blue smoke is water getting into the combustion chamber. The car can run like this for a while. Lots of times the car will run like normal besides the smoke. But the passage in the gasket will continue to get bigger and lead to more serious problems.

I had the same problem, whole new radiator, new hoses, new thermostat, and still overheating. What the problem was for me...bad radiator cap...all that money and a $20 fix...try it?

sounds like you have a blown head gasket.
be sure engine is cold, open water tank be sure it is full than start car with tank open see if you see bubbles in the tank. If so possible head gasket blown.

Are you getting water in the oil?
Are you burning white smoke?

Depending on the moter size, it could be an intake gasket leaking as well.

2.0 has thermostat mounted to head and hose to Radiator, 2.4 has thermostat below radiator cap.

Best thing to do is have Radiator pressure test done and see where the leak is for sure. There are dyes that you can add to the radiator and you can see leaks with UV light.

Good Day,

White some indicated that coolant is burning off. It could just be a simple leak which is burning off of the hot motor. It could also be a bad head gasket(probably what you don't wanna hear), One indication that it is the head gasket is white smoke coming out of the exhaust, this happens as coolant gets into the oil and is burned off then exhausted out the back. Possible causes for the overheating include, low coolant, coolant leak, thermostat, water pump and or water pump belt, or head gasket.

If I were you I would drain and flush the radiator, then fill it with new coolant, and change the thermostat, provided you have no white smoke coming out the exhaust.

hope this helps for now