Is This part genuine ? If no, may i toss it ?

 

That's aftermarket. Bought one similar to that for my Mazdarati 4 decades back....

 

Not OEM. Dentsides didn't come with coolant overflow. Also, your windshield washer tank is not OEM.

 

Is it only to ovoid to spread overflow cooling liquid on the road or is there an other purpose ?

 

It keeps the coolant from deteriorating as quickly as with an "open" system, since it keeps the radiator completely full. Also reduces corrosion in the entire system.
That is, if the system is working correctly.

 

IF working correctly, it will allow any overflow to be drawn back into the radiator.

 

X2 not OEM at all, but if it is working like is should why remove it? Same for the window washer fluid reservoir, yea NOT OEM but it is works, roll with it.

 

I’m not sure it works well cause it’s alway empty, this is why i wanted to toss it

 

If you are in France, maybe the closed system was something put on vehicles for the French market.

 

Our systems won't suck back any coolant from an overflow tank. Unless you have a different radiator and cap. Years ago, I looked into this as I wanted the security of an OF tank. I learned that it just wasn't designed for it. Somebody correct me if I'm wrong and please provide proof.

 

I think you just need the correct cap, the radiator can be the same.

 

I added one on my F100 along with the different radiator cap needed for it and it works fine.
Bob

 

X2, mine came with a different cap.