You will not have a motor if you let the temp go to 120C. These temps will kill this motor warping the cylinder head. You should be under 105C in trafiic with the a/c on. Check your thermostat IMMEDIATELY! This should fix it. If you are having overheating problems you may mave a blown head gasket but it does not sound like it. Check your engine oil for coolant and your coolant for engine oil or trans oil. Do not neglect this problem.

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1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T