'93 ES300 overheating

My '93 ES300 has had a problem causing overheating in certain situations (long trips) About six months ago, I took the car in and the mechanic
flushed the radiator and replaced the thermostat. The car has been working fine up until yesterday, when I took a trip up to a major metropolitan area on a hot day and had to pull over several times due to temp gauge shooting up. On shorter trip (up to 30 miles) the temperature does just fine. I'm going to take it in next week, but I was just wondering if there was anything I could check myself before doing so. Car has plenty of antifreeze and oil.
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Make sure that the electric cooling fans are working properly, that the coolant has the proper mix, and that the timing belt is not beyond its replacement interval.
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Ray O
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Check to see if coolant level is being maintained. If not, you may have leak in radiator seam. Check along edge of top/core seem for evidence of fluid leak.
Leak causes loss of pressure which lowers boiling point and allow fluid to boil off.
Happened on my SC400 a few years back.
Xplant
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