thermostat operation - cold radiator

[andycook]

hi, just want to check thermostat operation - on my 3.0 TD 4runner,

I recently replaced the rad cap, and the system seems to pressurise now, it didnt use to.
The thing is, even after a longish journey - say 25 miles,
the bottom hose of radiator doesnt get that hot, the top of rad and top hose does. The heater works ok, blowing lots of hot air.
I am wondering if the thermostat is opening?
as maybe it isnt and its stopping flow of coolant from rad then trhough thermostat, and back pressure is stopping coolant also flowing through the rad?

i guess i should get a new thermostat anyway, as the 4runner has done 140,000 miles

[Vagrant No2]

If the thermostat was stuck shut you would overheat , but if faulty or stuck open it would run cold and have a warmish heater . Sounds like all is OK because bottom hose is supposed to be alot cooler then top as rad is designed to cool the coolant .


Rick

[andycook]

radiator was stone cold too, apart from the very top, just below the top chamber, however, the viscous fan runs most of the time, thats something else im trying to sort out - it didnt work at all recently!