Two problems related to radiator have been reported for the 2010 Mazda CX9. The most recently reported issues are listed below.
We were sitting in a parking lot waiting on a pizza. We noticed the a/c wasn't cooling, and then noticed the car was starting to overheat. (this was the first time ever). We checked the radiator, it was empty. We purchased coolant and filled up the reservoir. Never saw any leaks. Car started but seemed sluggish like the battery was low. We got our pizza and drove about 6 miles where we parked till we took it to the dealer on Monday. Our mechanic called me later to tell me that the water pump had failed and that it had leaked into the oil pan and we would have to have the engine replaced. The repair total for my Cx9 is at $9k. We have 108,000 miles on the vehicle. My vehicle is still sitting at the dealer.
On Jan 12, 2019 we were driving home and without warning the temperature gauge spiked and the check engine light came on. The engine stopped and I was able to get the vehicle off the road. I looked to see the coolant reservoir was empty. I was able to refill it, thinking possibly there was a leak. It got us home safely. The next day, enroute to the radiator shop; the same thing happened. After a tow home, then a tow to the radiator shop and eventually a tow home, it was diagnosed as a water pump failure and now a new engine is the answer for the repair. There was absolutly no warning to this happening and the water pump is internal. I understand that the pump can/will wear out. I get it. Where it's located is a joke and I've read it's at least a $1500 - $2000 fix, just for the pump replacement. The main issue is the no warning whatsoever!.