Hi all

As some of you might know, I have installed my thermo fan and removed the stock mechanical fan. Now I am puzzled as to where is the best location to put the thermo switch that will activate it.
I already have at the bottom hose a stainless steel T pipe that connects the hose coming from the radiator and the hose then going into the engine block.The other T part then is to connect the flow from the back of the cylinder head. I want to take this thing and just let them drill and weld a nut that has the correct thread for the sensor to the opposite side of the T that goes to the back of the head.

Some people say I must put it at the top hose. Currently this hose has a obscure bend to connect it without collapsing on itself. Now to put the sensor in here and also keep the bend going, I will have to make a stainless steel connector with a 90 degree bend. On this bend I will let the engineering place weld a nut that have the correct thread for the sensor.

My problem: Lets say the normal radiator pipe's inside diameter is 40mm. I am now going to put a 90 degree bend in this pipe and this internal diameter will be about 30mm. So this will cause a partial obstruction (90 degree bend and a smaller diameter in this stainless steel bended pipe)in the flow from the engine to the radiator.
Will this not cause maybe some flow problems?