Dear Mr scotty,
I am a big fan of your car videos , you really have a great long experience , if I was near your state you would be my first choice for any maintenance or problem I face (It's not a compliment it's the truth)
4 months ago I changed my brake fluid in my car which has about 110K km done and I regret to do that mistake because then I had my brake pedal goes down slowly (sinking) while pushing it down and the problem is significant while stopping in traffic, so I had my brake master cylinder changed with a new original one, then I drove the car for 2 minutes and the servo (Brake booster) started hissing and the brake pedal went too hard to push while driving so I had the servo changed but this time by an used original one because no new part is available in my country even at the dealer itself.
Now I have the brake fluid, brake master cylinder and brake booster changed but I still have a little problem . After I stop my car and turn the engine off the brake pedal goes up and becomes very hard to push and goes back to normal after turning the engine back on (I know that after turning off I have to push the pedal 2 or 3 times to become hard not just by itself for no reason) ,second problem: sometimes when I put my transmission on D or R the brake pedal goes up and down and even while stopping in traffic I feel the pedal goes softly up and down.The last problem is sometimes not always the pedal goes down very slowly and the car start moving (Like I have my old problem back but in a fewer way this time)
Now I really need your help to tell me what to do because my mechanic doesn't have an answer or solution for my problem (I may have to mention that my car has an ABS on it)