I recently had work done on my Volvo 2008 V50. The front axles were replaced, new brake pads in front, and new calipers and pads in the rear. When I got the car back the brake pedal would go to the floor… turned out the master had been compromised when the mechanics were bleeding the system. That was replaced (at no charge) as well.
All seems well except that now when I brake suddenly, which happens a lot in So Cal traffic, I feel a thump under the floor. I don’t hear anything but can feel thump or a knock right under my feet (driver’s side). This only happens when braking quickly. Braking at a slow speed does not produce the thump.