I recently refitted the caliper spring clips on my '16 XF and now I suddenly have a low brake pedal?? Within the past year I painted my front calipers and have since occasionally noted a rattle at low speeds over rough surface. The brakes have since otherwise worked beautifully. Following a recent non-related trip to my local dealer service, I was informed that the source of the rattle was the spring clips installed improperly. Ouch....self inflicted DIY issue. Ok, so I returned home, tail between my legs, and pulled the wheels and refit the clips as shown in the photo. No more rattle but I have a low brake pedal. Brakes function but there seems to be low or no power assist. Without the car running the pedal is solid but slowly sinks as soon as the engine is started. Note I have never removed any of the brake lines, The brake system has no apparent leaks, the reservoir is full, and the caliper slide shafts are well lubricated?? Whuh now????

Online I've found discussions of failed brake cylinders that show no leaks, air in the system etc.

Any thoughts will be welcomed before I sheepishly return the car to my dealership for a $$ blood letting.

 

Does the pedal get harder when pumping up the brakes? Air in the system symptom. Bleed the brakes. Be careful with a "full" brake fluid reservoir. It's normal for the fluid to reduce level as the brake pads wear and topping off the reservoir leads to a mess when new pads are installed and the pistons pushed back with fluid exiting out the air bleed hole in the filler cap. I don't see how re-positioning the clips has anything to do with the low pedal. You'd know it if the power brake assist function went away as the car wouldn't be safe to drive.