So my A4 B5 has 125k on the clock and I'm getting the timing belt changed as well as the hydraulic tensioner. The log book says to get the timing belt and tensioner changed at the same time. I have read other forums which state that while getting the timing belt changed you should get the water pump, thermostat, A/C belt, cam seal and crank seal changed at the same time. Is that necessary or too much overkill?

 

If it's a moving part and it has to be removed to do the timing belt then go ahead and replace it. Only replace cam and crank seals if they are leaking.

 

You really should change everything the timing belt rolls around. That includes the water pump. Its buried underneath the timing belt, and if it fails the timing belt goes slack. Cam and crank seals are nice cause you're right there, but not necessary. I wouldn't do the serp belt unless it looks bad. You really aren't redoing much (if any) work if you have to do that a month from now.

 

What those guys said ^

and a +1 on the serp belt unless it looks like it's getting worn