It cannot be much else if the pipes are different temps,this clearly shows that the water is not moving properly.

When the engine is hot,is the header tank water warm.

If it is,lol, blow into the header tank so you move the water around,then check the header tank water temp, this will now be really hot!

LOL, this is what i did on a rst 2 and it did turn out to be the water pump.

May sound stupid, , but it will move the water around the engine!


Dave.