Address problems in a C8

I have an address problem and it is as follows: in cold and after about 5 kilometers the address begins to get hard being a risk to drive the car. In the house they found corrupted hydraulic oil and they do not take care of the possible fault and trying to strain a repair that they do not know if they solve the problem. If there can give me any solution, I would appreciate it very much

Hello, you can get information from the manual here: Citroen C8 Peugeot 807 Mechanical Repair Manual

I hope and serve you