Does it heat up and boil over pretty quick, or does it take a while and heat up gradually? If quick then I am guessing head gasket. If gradually then I am guessing clogged radiator. Based on what you said I am guessing head gasket but that is just a guess. Can you look into the radiator and see any of the tube ends? That might give a clue as to the condition, whether they look clogged or not. I don't have specific knowledge of that car however. Have you tried searching on "190 overheating" etc? Head gasket problems are often systemic to certain engines.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra