So, I finished replacing the water pump on the 2012 Mazda 5. Better than an Audi job, but still not great.
First, you will need to be resourceful with your brain and your tools to get that thing out. You'll likely need a long handle 8mm wrench. I also did the thermostat/housing and it was not easy, but got it done. You will eventually need to jack the engine about an inch up to get the pump past the frame rail.
I'm not a mechanic and this is only how I did it. Here goes!
First, drain the coolant from the driver side petcock of the radiator. Catch and recycle.
Remove coolant overflow tank.
If the serpentine belt is on, try to loosen the 3 pulley bolts (10mm) with a wrench while the belt tension is holding it. I already had my belt off for other reasons and still managed to get it off by putting the 10mm wrench on and using a bigger wrench to wedge the other two bolts so I could hold it. Get the pulley off now and clean it well on both sides.
The pump has 3 8mm bolts holding it to the block. Get these off however you can. I used a long handle 8mm wrench. Under the car you'll need the long wrench since a socket doesn't fit.
Now, to get the pump out you will need to pry and jiggle, and tap and pry. Go underneath and tap and pry, go on top and tap and pry; repeat. Eventually, it will pop off (and a little coolant), but you cant get it out just yet!
Remove the 2 17mm bolts holding the engine mount to the frame rail. Jack up the engine about 1 inch and you can wiggle the pump out of there now!
Installation is the reverse. RTV is not recommended on the new pump since the new O-ring will seal everything just fine. There is a reason the factory didn't use sealant!
Be VERY careful to not over tighten these little bolts. They go finger tight, and then not much more with a small wrench. Use light thread locker too. Don't strip the block threads! Sorry, I don't have torque specs, but it is amazing how very little torque are on these little 8mm bolts. Don't worry, the o-ring will seal, it's not a gasket situation here.
Using light thread locker, put the pulley bolts back on as tight as you like with your wrench. After the belt is back on, make sure they are tight again.
Install coolant tank.
Fill with new Mazda coolant (green).
Start it up and check for leaks. Watch and fill tank as the system purges air over the next 100 miles.