How do you know the water pump is bad on a cadillac cts

SOURCE: Need repair manuel for 2004 Cadillac CTS

Similar to obtaining an owner's manual, you can obtain a repair manual from the same sources identified in this handy, diagnostic article:
http://yourhandymanzone.com/Your_Handyman_Zone_How_To_Pages_Vehicle_Car_Zone_Cars_Trucks_Vans_Owners_Manual.htm
This should defintely help
Brad

SOURCE: Replace 2005 Cadillac CTS water pump

drain the coolant.remove belt by rotating belt tensioner cllockwise. water pump pulley will require a holding tool to keep it from turning while removing bolts. access to air ratchet can sometimes eliminate the need to hold but be careful cause thats a good way to skin some knuckles. also make installation more difficult to obtain proper torque. after pulley is off just a few water pupm mounting bolts remain. clean and dry gasket surface very well before reinstalling.

Testimonial: "Very quick with a response, and good info!"

SOURCE: Need to replace water pump on a 03 Cadillac cts I

I do not mean to be hurtful and it will take some time to do. Maybe all day if you have no experience. If you need instructions just maybe you should have some do it for you.

SOURCE: 2005 cadillac cts base water pump replaced by

If there is no indication of overheating, the check coolant light is probably triggered by a sensor indicating low coolant level. It's also possible that there is air trapped in the cooling system from when the water pump was replaced. Trapped air could cause the sensor to throw the trouble light. Bleed the air from the cooling system and see if the light goes out. You may have to clear the light after bleeding the system.