I sprang a leak in my radiator about a month ago... and I simply did not have time to replace the radiator myself, so I took it to a mechanic. The mechanic replaced the radiator but he reused my old cap.
Two weeks later my water pump broke (basically the bearing broke and the pully was flopping around). Upon replacing the pump (what an ordeal) I saw/read in the instructions that I should also replace my radiator cap along with the new pump!
Now I'm wondering if re-using my radiator cap precipitated the failure of my water pump. Also, how common is this problem? Should I expect a mechanic to replace the cap with the new radiator (I know that should have checked it myself)? I didn't even think about it until I read the water pump instructions, at which point I looked and found my old radiator cap was still in use.