LC 80 overheating petrol

Sounds like the radiator needs cleaning out, a common fault on 80 series.

I use to get my radiator profesionaly cleaned every year . Scale breaks off the block and blocks it up. Overcame the problem in the end by hot tanking the engine

Another way to check if its radiator or not check for cold spots on the radiator fins might have to do this buy stopping motor quickly and checking wouldnt like you to lose any fingers on those blades. Regards Steve

If you can't get it booked it, just drain the rad, flush with a garden hose and refill with genuine toyota coolan, change the radiator cap and see how she goes, might just get you through till after chrissy and will only take an hour or so to do at home.

When you get your Rad propery cleaned, get the viscous fan rebuilt too.

Could be anything from clutch fan not cutting in to normal operation on a hot day....3/4 is still within normal range....another novel thing to try is put the heater on flat out ontop of air when it gets to 3/4 and see what that does...
As a starting point...i would run hose through rad from engine side and see what colour falls out the bottom...
Andrew