1990 Chevrolet Monza

Engine Mechanical problem
1990 Chevy Monza 6 cyl Two Wheel Drive Automatic 200k miles

I have a 1990 Monza Classic 2.0 with 200 thousand km.
It tends to over heat when in slow moving traffic with the A/C on and also when going up a long hill. Once back on level ground, going down hill or moving steadily in traffic it returns to normal. The temp is Ok when A/C is off.
Could it be I need a new or different rad?
P.S. I am in South America where the average temp is 35C daily.
Any help or ideas is greatly ppreciated.
Emmett Osullivan
Emmett Osullivan
January 11, 2010.

See if your fan is kicking on when you turn the a/c on. If it's not electric then check your fan clutch if you have one, it should lock up when heated up. Also check your fan shroud, as it should come almost up to the fan to suck in air when it's hot like that.

May 18, 2010.