E53 4.8IS Braking stuck
 

Dear All,
i had a strange situation couple of days back.
when i engaged the the car to D i felt the break paddle is very hard
i tried to brake , but the paddle is hardly moving and the car is not stopping, i had to use the hand break to stop the car
no alarms on the dashboard
after few trials and switching the engine on/off
steering the wheels complete turn to right then left
then it works fine again
any body know what could be the reason?

One of my buddies had a similar prob, he got trifecta lights and i think his brakes ended up being stuck (as in not braking and brakes engaged)

But it was the master cylinder so check that, his could have gotten stuck on the brakes, yours might be stuck open and not braking.

+1 for master Cylinder.

possible master cylinder , but wouldn`t hurt to bleed the brakes, I doubt its air in the brakes though.

I went to dealer to check the car.
He advised that the brake servo need to be replaced
I'll keep u updated
Thanks

4.8X5 was mentioning me on this situation…

what happen to mine was
i was on the highway, driving normal around 80-90mph….
cuisine then i try to slow down as a vehicle went in front of me suddenly and from that point the pedal felt funny( pedal was stiff to a point of not moving) and the car suddenly start to slow down like the caliper was "stuck" so i quickly went on shoulder taking 3 lanes to move and after i stop completely turn of the car waited for like 5 mins hoping the X would go on "reset mode" then i started her up, put her on D and the car is Stuck,stopped,seized IT WAS NOT MOVING…so i forcely drove it exiting the highway for about 1mile stop on gas station and called Tow Truck….put her at the shop, first was Brake Module, which was under the steering wheel,..

next day,
drove her to highway and BOOM!…brake seized AGAIN…drove her back now all 4's are smoking, dropped her off again,
Now, Brake Booster is Going, Replaced,
MC Replaced also, suggested bleed the lines,…at this point This acted up on Monday, and MPACT is Saturday….with all these process of elimination i don't have time for it so i gave them the GO word to just change the whole brake system,

they ended up bleeding the lines 7 times as everything was changed except the calipers(which was fine) they said that the lines was causing some soft force when you press on brake pedal to a point it was going almost to the floorboard 7x later it was back to normal …shop called me Friday night, left keys and took it to Mpact M.D. a 4hr drive…..


first suggest to bleed the lines, check MC, then Brake Booster and Fluids

lol this is scary the shit out of me as I sometimes "step on it". Why is this happening? is it because the brake fluid wasnt flushed at the time? this is scary to say the least.

I've replaced the brake servo assembly and now the car back to normal.
Thanks to you all

Lots of threads are scary--maintain perspective--I have to remind myself often.

I seem to have a similar situation. It doesn't happen all the time and since putting the x back on the road after sitting 6 months I have noticed it twice over the past 8 weeks. BUT, my brake pedal effort is normal, not soft or hard. The car brakes without locking up or shuttering. HOWEVER, the other day the car was bouncing down the road in D at 45mph and after braking a few times I smelled brake fluid. I didn't see any drips or leaks on the drive or by the wheels in front or rear. Two days later I take the car to the shop and it drives perfectly. No issue but there was a very, very slight brake fluid smell. Finally, there is a vibration in the steering wheel when the car is idle after warming up and sitting at a light. When I drive from stop to 55 there is no vibration in the wheel until I stop again. I have never had any vibration in the steering wheel, I've owned the X for 9 years. 178K .