i took my car out for a spin on the weekend and it ran hot, close to boiling. was only about 33c degree day and didnt go over 70kmh. it doesnt have a thermostat.
what could cause this suddenly??

, the coolant was not low even tho it was sitting a couple of weeks.

pipe blockage, low oil levels. mine randomly does it as well..

Have you recently removed the thermostat?

Often what hapens is when the thermostat it first removed the water flow is so great through the block that all the loose rust and scale gets picked up from the bottom of the block and gets dumped straight into the top of the radiator, blocking alot of the tubes..

BTW, all engines need to run a thermostat or at least a restrictor in place of the thermostat to maintain block pressure. Block presure is very important to stop localised boiling around combustion chambers and exhaust valves, the radiator cap presure is not sufficient. EDIT (you might get away without one putting around the streets)

Yeah give it a good flush and put a New Thermostat back in, they serve a purpose like wheel nuts

thermostat was out ages ago not recent, maybe i just need to get the whole thing pressure cleaned out, and then run thermostat. im thinking maybe something came loose and blocked up somewhere, hopefully not the block.

yeh wheel nuts? dont u like it when your wheel comes off and overtakes your car and several others, whats wrong with you. haha,

Go for the power flush option. It cant hurt. If anythign breaks as a result, you can fix it while the car is in the shop, not when you are on the side of the road.

And for the theromstat, in my 253 patrol, I originally removed the little floating pin, then drilled another 2 3mm holes. That made a huge difference, which really surpriesed me. If that then fails, remove the spring and bimetal core, but leave the plate in place.

If that doesent make a difference, then there is another problem that needs attention...

How manys k's on ur water pump? It might be on the way out?