firebane

Had an issue with a near boil over the other day when its been -25 celsius where I live.

I thought maybe the thermostat so I swapped that out and now when I run it for short periods of time I can get the lower hose warm, upper hose hot and the radiator relatively hot.

If I go for any long period of a drive the radiator becomes stone cold as does the lower rad hose again.

I've changed the radiator, water pump and thermostat. I have not changed the fan clutch yet though but thinking that could be an issue?

When the truck has been running and then cools down if I try to turn the fan blade I simply can't and it won't move.

My understanding is when a fan clutch is cold it should spin freely for 1.5-2 turns?

Trying to get this thing reliable again

Hatsuwr

That's cold... A coolant mixture that is less than ~40% antifreeze or more than ~90% antifreeze will be frozen at -25° C. Contaminants may raise or lower that freeze point, so it's best not to be close to either end. Lowest freezing point is achieved between 60%-70% antifreeze.
You sure your ratio is correct?

Fan clutch sounds like it might be faulty, but that shouldn't cause the problem (by itself at least).

Is there any chance your lower radiator hose is collapsing when the pump starts spinning faster?

Just curious, what was the indication that you were near a boil over?