I have a 2011 2.5 ranger that keeps running hot , the top radiator hose is hot but the radiator and bottom hose are stone cold? The temperature gauge goes to to the red but when i stop it quickly goes to normal? I've changed the water pump and thermostat, but it is still doing it so now I'm bit stuck ,

 

Welcome to the North American Ranger forum

You have a T6 international Ranger which is different than ours.

But cooling systems are pretty standard on vehicles

You have the Mazda L engine, 4cyl 2.5L L5-VE, Ford renamed it 2.5l Duratec

If upper hose is hot but lower hose is not then there is a lack of circulation.
Radiators provide 15-20deg of cooling, so lower hose should be 15-20deg cooler than upper hose

The water pump provides the circulation thru the engine and then as thermostat opens warmer coolant flows out the upper hose thru the radiator and back to the engine thru the lower hose.

First thing to check, since you have a new water pump and thermostat, is the fan belt routing, look for the fan belt diagram in the engine bay, make SURE water pump belt is on the correct side of the pulley.
On most serpentine fan belt setups it is possible to route fan belt so water pump spins backwards, I know "you know" its correct, just check it, because if it is backwards you get EXACTLY what you described, hot when running then cools down at idle.

Hot upper hose and cold lower hose means no circulation thru radiator, so next step is to replace radiator, if you deem water pump and thermostat as OK

 

I've changed the radiator, thermostat and heat sensor . But I'm still getting the same problem? I've checked the engine with a hand held thermometer and it's reading ok ?? . The heaters are working fine also ,
I've checked we put the water pump is
on correct and to me it can only go on one way ? .
I'm not loosening coolant or oil ?
If I travel around below 55mph it doesn't happen ?
When the needle goes up to the red , if you take your foot of the throttle it goes down as fast
as it went up ?

 

Reads like an electrical issue not a heat issue

Engine temp comes from the computer not the engine, in 2014
The computer gets the engine temp from the CHT(cylinder head temp) sensor on OUR 2.3l Duratec engines, so may be the same on your 2.5l Duratec?

So could be sensor issue or HEC cluster issue

Google: ford hec cluster

There are tests it can run