[jhv48]

So far, problem solved.

Replaced the 180 thermostat with another 180 and this time drilled a single 3/8 inch hole at the 12 oclock position.

Temps steadily climb to the 80C mark where they stay until I get caught in traffic and then can creep slowly up to 95C where the fan kicks on and sends the temp back to about 90C.

No more spikes to worry about. Mild cruising drops the temps to about 80C and freeway speeds drop it another five to ten degrees. Hard to believe a $7 part can cause such a problem.