Peugeot 207 rear wheel brake cyclinder replacement

Dear Bryan,
Because it will take many pages of instruction here on this web-site, we would like to recommend you go to a public library or a car parts store and get a repair manual to follow the instructions.
Those repair manuals are year and model specific.
In a nutshell, here are the steps.
1) Block front wheels.
2) Jack up truck and remove rear wheels and brake drums.
3) Remove rear brake shoes, being careful to remember how you did it.
4) Install new brake shoes.
( If the rear wheel cylinders are wet, replace them.)
(Remember to retract the adjusters as the new linings are thicker than the old ones.)
5) Reinstall the drums & wheels, and lower to the ground.
God bless your efforts.

the wheel cyliners need to be replaced ,that is most likely where it is leaking , recommend bleeding the brake system both front and rear after changing the rear wheel cylinders

remove rear wheel , pull off the brake drum , you may have to use two flat blade screwdrivers one eachside to prize the drum off,clamp the flexable brake hose behind the brake assembly so fluid does'nt drainout,at the rear of the back plate you will need to disssconnect the hand brake cable usually a spring needs compressing by hand and then are able to disconnect the cable from its seating,take a picture of the brake shoe assembly before dismantling it so you know where the components go when re building, there will be spring loaded pin holding the shoes in place ,with a pair of pliers push and twist the flat washer so the pin head comes through the retaining washer you should then be able to lift away the shoe's and mechanism , next at the rear of the cylinder disconnect the brake pipe and the two retaining screws , fittings is the reverse , if you can get a workshop manual for the vehicle this will give step by step guide a tips for that exact vehicle, once back to gether unclamp the brake hose and bleed the brakes , take your time and if not sure if it looks right have a look at the picture or alternatively take the other wheel and drum off to check good luck

there is some pics from brake sistem maybe yours is little diferent but check the hose on the outside

You must find mounted on the right side of the rear axel,a regulator for brake pressure (weight)I thing there is your problem.