When you get beyond 110C, do you hear the clutch fan and electric fan engage? The electric fan should be in high gear but it might be hard to distinguish from the low speed when the AC compressor is engaged.

If the clutch fan isn't engaging, do an archive search on variations and combinations of 'Toyota silicone fan clutch fluid'.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD