What is the second coolant reservoir for in the ATS - with the tiny cap?

caddydriver9999 · Sep 17, 2022

what is the second coolant reservoir for in the cadillac ats with the tiny cap? Is this suppose to be filled too?

Excalibur · Sep 17, 2022

It`s an overflow tank for when the coolant is either filled too much or expands due to heat.

caddydriver9999 · Sep 17, 2022

thanks. I haven't worked on newer cars that much so this is the first time I am seeing this.

jeffbazell1 · Sep 19, 2022

Don't let it run dry. There's a fill mark on that small tank.

SaveTheManuals · Sep 23, 2022

^that. Owners manual also shows you how to fill it if you have one.