T4 2.5L Diesel Cooling system question

[klxnsw]

Hi Guys,
I am currently experiencing some problems with my cooling system. Once the car wams up to 90 degrees c i am noticing that the thermo fan does not kick in. Also as the car warms up it gets to 1/3 temp then drops back to zero and then gradually gets back to 90 degrees (half way) and stays there.
The temp of coolant in the coolant expansion tank is approx 87degrees c and the temp is reading 90 degrees c. However the top radiator hose (water in ) is hot approx 87 degrees and the bottom radiator hose going to the thermostat is really cold.
My gut feeling is that I have a dodgy thermostat (stuck open??) and that is why the hose is cold. Is it possible that in this situation the engine re-circulates water internally and by-passess the radiator?? and hence bottom hose remaining cold??.

It has me puzzelled as normally a thermostat stuck closed would cause the temp to get really hot and a thermostat stuck open would cause the engine to be operating at less than 90 degrees with the bottom hose getting hot.

I dont know why my bottom hose is pretty cold and the thermo fan is not kicking in.

Any advice would be great

thanks

[Transporter]

It could also be a blocked radiator.

[klxnsw]

Thanks, I will check the radiator when I change the thermostat.

Anyone else having found the same problem?? Surely I cant be the only one who has experience this