2001 Audi S4 - Thump after fix

Recently the car had coolant over flow pipe replaced and the next day I was getting a thump in the front when I put the brake on and car comes to stop. I talked to the Audi dealer and they told me i is the axle. Never had this sound until this repair. The wheels feel stable at high speed.

Ok, why would the Audi dealer lie to you? This 18 year old car must be a gold mine to them.