I provide some extra info.
Here is a picture how it should be connected.
Connect things as stated in my picture, and try to mount the tank as high as possible.
The 77**** numbers are the Renault numbers for the tank.
The blanc cap is 0.7 bar but Renault could not deliver, and I doubt if it releases the under pressure in cool down..
You have to go to the Peugeot dealer for the cap.
It is Peugeot number 1303.40, and it cost around €8.-
It is 0.8 bar (12psi) wich is exactly what is needed.
Also I tested the under pressure release, and that works fine.
There are disadvantages for this tank, and I don't now yet if it will work properly, but I will find out in a few weeks.
I am pretty sure it will do o.k.
The original tank is 2.5 litre.
This one is 1.6 litre.
That is a liter less in the system.
Also when water is released because of overheating, there is no output to mount the hose that leads down the car.
It will boil over at the cap. (who cares)
I will have to test it out in heavy stress for the engine in hot weather to see the engine not get overheated.
It has to be summer for that, so i am not in a hurry to finnish the job.
I calculated 0.5 litre expansion needed in a temperature rise of 80°C for the 11 litre coolant.
The max level has to be between max and min indication on the tank to give it room to expand.