04 986 Whistling after coolant fill
 

I have a 2004 boxster base and I had the water pump replaced about a month ago. After getting the car from the shop I noticed that when I would start the car there was a significant whistle coming from the engine compartment. I tried to vent the system using the vent by the coolant cap. Is there something else I should be looking at?

If the whistling happens on a cold start it is the secondary air injection pump, SAI. It is a pollution control device that is on for a short period as the car warms up.

Adding to what Anker said,
http://986forum.com/forums/uploads02...1564692660.jpg

Related to the water pump replacement, I'd check the belt and pulleys.
https://www.pelicanparts.com/techarticles/Boxster_Tech/05-BASICS-Belt/05-BASICS-Belt.htm

Unrelated to the water pump replacement, a whistle can be from a loose spark plug.
https://www.pelicanparts.com/techarticles/Boxster_Tech/07-ENGINE-Plugs_-_Coils/07-ENGINE-Plugs_-_Coils.htm