Hey all, I've got a 2016 IS 200t. I picked it up in 2018 with < 20k miles on it because it was cheaper to buy a new car than to keep driving my rx8 @ 12-14mpg across Dallas every day. I've been working on rx7/8 for 20+ years, and it's a Mazda, so I'm no stranger to over complicated jobs. Thanks to COVID, I am only up to 30k miles on the IS.

Out of nowhere I started having an overheating issue. It was freezing cold the other day and I realized that the heater wasn't getting coolant because the heater wasn't working. I got the coolant over temp warning but by the time I pulled over to shut it down the temp fell back into range and the heater kicked on. I drove it again the next day and got the same thing. My first thought was thermostat so like a good shade tree, I ordered both of them.
I found this video:



So I took the thing apart and then realized that the video was wrong. I have to remove a whole bunch of stuff to get the second (smaller) thermostat out.
This is the correct location:
I have the first one out and replaced but I've got two questions
1. I don't know how the coolant is routed. Does the fact that I didn't have heat indicate that maybe it was the larger one and I don't need to mess with the second one?
2. If not, if I change the second one, should I just go ahead and change the water pump? I might have been a little low on coolant. I poured maybe a quart into it when I got home, and that put me just below the max line. I've read a bunch about issues with the water pump but it seems crazy to have a water pump issue at 30k miles.

Thanks

 

I thought my is200t in 2019 with 35k miles. The water pump went out @ 41k miles. I am now up to 170k miles, had my first issue today with high engine coolant temp warning. Went right back down, but noticed my heat was not working the past couple of days. Best of luck to you!