Hello, I just bought a 2007 Mazda 5 and was told by the PO that the radiator was just replaced before parking the car and it sat 6 months. I installed a new battery and it started right up and I let it run until I felt heat, test drove fine. I turned A/C on and cooling fans ran so I bought it.
On the way way home I drove 30 miles on hwyand temp gauge was normal until I had to slow down for traffic jam, only sat for about 3 minutes and the gauge quickly went up to almost all the way and traffic broke I was able to speed up and temp gauge came back down to normal. Upon driving about 2 miles in my neighborhood the gauge quickly ran up to hot again but I turned the heat on full and it began to cool down and I shut it off before it pegged, however the moment I shut it off the radiator literally burst open and lost all coolant and destroyed the radiator. I am waiting for a new radiator but in the meantime have removed the thermostat and tested it and it’s fine. I did notice the cooling fans were not running when I heard the radiator blow but thought that may be due to the lack of coolant at that moment .
I would greatly appreciate the advise of anyone with experience.

 

There isn't a coolant leak anymore as far as I can tell, and there isn't coolant in the oil. When the shop replaced the radiator in May they said the head gasket was fine.

 

Check for leaks underneath. Make sure the hoses are clamped securely. One way i check my water pump is let the car run for about 15 min and i touch the hoses after. They're gonna be hot but if the one on the bottom is luke warm and not piping hot it could be the water pump. Any Tutuapp 9Apps Showbox exhaust fumes? If so what color?

 

If the job wasn't done well the t-stat can be perfectly good but not get up to temp due to an air pocket. I had that happen on an old Volvo that was still overheating after doing a replacement. Put a tiny hole in the top that let the air escape and the problem went away.

 

Reading your first post recommendation first after new radiator is installed before removing any other cooling system parts or assuming anything: Pressure test the cooling system. You may also want to do a Block chemical test to see if there are trace exhaust gasses in the coolant.

Your year engine uses a thermostat that will relieve any air after the first warm up in the cooling system. Besides what your specific problem is would not be air in the system. In actuality very few engines have issues with "air pocket" like some engine a few decades ago. Most were cured by having what is called a "giggle valve" on the thermostat. And the even fewer were caused by a bad designed head that most auto manufacture quickly cured with subsequent productions of the engine.