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How long does it take to overheat?
The first thing i would recommend is to have the cooling system chemical tested for any signs of hydrocarbons to rule in or out the headgasket.
If none are present, then you will need to consider things like a restricted radiator, either internally, or externally, it can get debris built up in the cooling fins of the radiator, and condensor, if it has AC, reducing air flow thru the radiator.
Also check the fan clutch operation (pretty sure it has one),,,if its not locking up ditect drive when hot, it wont pull enough thru the radiator.
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Thanks for asking!