Radiator Thermo switch

[kevtherev]

Ran it up and got to three quarters again fan came on but just for five secs temp still rising !!

the fan will switch off because the coolant in the rad has cooled enough to switch it off.
If the circulation of coolant is poor due to air in the system, gunged up radiator, or a failing pump then this will happen

.

I think stove has solved my problem ?? If the flow is restricted through the rad then the thermo switch isn't picking up the correct coolant temp?? Which would prevent the fan coming on at the correct time and allowing to temp to continue to climb? It makes sense to my thinking, but I'm far from being an expert

perhaps my answer was too technical

[HarryMann]

Yes Kev..

In short, if very little of the rad water is circulating through the engine it cannot cool it down much.
If the heater system is unblocked and working well, that could make a big contribution, being separate.

There might be a few cacky hoses and pipes around too.

Isn't the thermostat housing a big undertaking on older vehicles?