Brake pedal problems

The brake pedal goes up after turning the engine off and goes up and down while pushing it down or while moving D to R

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)

Best Regards,

Qais

Comments (2)
No. 1-2
QaisRshwani
QaisRshwani

well , I changed the brake booster again and it's now ok and I changed the front brakes , renewed my brake rotors for both front and rear (if u understand what i mean) and I bleeded the whole system out using brake bleeding machine (and the master cylinder was changed like what I mentioned before) but ... I still have a serious problem that even my mechanic wasn't able to recognize : while I'm hitting the brake pedal down in full stop situation the car makes noises which feel like I'm releasing the brake pedal in which I'm not and the car feels like starting to move (actually the brake pedal starts to sink slower than before like it's unnoticed this time) ... I don't know what the problem is , Is it the ABS itself ? Are brake rotors need to be changed ? or other things ? Kindly seeking your help
Many thanks

ScottyKilmer
ScottyKilmer

Editor

classic signs of a bad brake booster even though you just changed it out. that or air is stuck in the system somewhere. Pay a pro to power bleed it out