Yeah, I agree. Just take it back in. They probably didn't bleed the system fully. I use an OBD2 gauge that connects via BT to my phone to monitor water temp when I'm driving and it's pretty insane how much of a swing there is while the temp gauge is just sitting in the middle. On a normal drive on the highway, temps can range from 195 all the way to 225 without it budging. It's crazy.

 

Decided to chime in here and bring this back! I have a '16 RRS V6 with 57k on it. Punched the gas hard on Friday night and coolant went all over the place with smoke and burning smell. Had it towed to my indy mechanic and he told me it was that valley coolant pipe and all the stuff to remove. Replacing the water pump and pipes is going to be around $3k. What a joy!