Brake issue when backing

[ponyv6]

When I was going backwards, brake pedal went lower and lower. After some level, it wasnt going down anymore and the brake force wasnt enough to stop the car (just the reverse gear and no throttle). I pushed the pedal harder and I felt a weird vibration and it stopped.

When I put it to "D" the brake pedal recovered after I moved about 20meters. and everything went back to normal.

it happened only 3 times and when I got to the dealer of course I couldn't show it.
It may be coincidence but it was always over 105 degree (the weather) when it happened

Brake fluid level is normal. brake pads are good.
2015 V6 16k miles.

I am worried that brakes will not hold when I am going forwards.
Any ideas?

Sponsored

 

[jasonstang]

That is very weird.
Vacuum leak in the booster?

 

[ponyv6]

I checked that area too.
I am also checking the place where I park my car.
I haven't realized any fluids.

 

[Jon|3.7]

did a google search, different car but sounds like the same issue

https://www.yourmechanic.com/question/brakes-don-t-work-in-reverse-how-does-this-happen

 

[ponyv6]

yeah similar. but mine doesnt do it always. so I havent been able to prove it to the dealer. also they dont provide rental that is why I dont want to leave the car without proving it

 

[jasonstang]

I don't think the brake booster is electric on the Mustang. I think you have a leak but why Is it doing in reverse is weird.
Would it be possible when in reverse, the drive train twist the other way pulling on something causing a leak?

Sponsored