Check the level of your coolant sa radiator at sa reservoir, pag okey naman the most common cause daw ng high speed overheating is restriction sa coolant flow usually a clogged radiator. Cavitation of the water pump at high speed is another cause.

One way to test is:

With a cold engine disable your cooling fans. Start the engine and let it reach normal operating temperature (your engine will heat faster w/ disabled fans).

Turn off the engine and feel the radiator for cold spots, if positive clogged radiator mo. Or else drain some of the coolant, and look for deposits sa loob using a flashlight. But the best thing to do is have your cooling system checked by a good mechanic.

Please dont forget to return the electrical connection to your fans. Watch out baka po mapaso kayo.