Working on my wife's car and the Mazda 6 forum is horrible. Comparing the forum to this one and that one is trash! But back to the question; recently replaced the thermostat because of a check engine light. Light went away, but thermostat kept blowing the gasket. So I replaced the water pump and thermostat. I used a high temp rtv with the thermostats gasket and it held up for about 2 months. Then it blew again. So I decided to re-do the seal since the thermostat was good. Burped the system and let it run, noticed it was at operating temperature but the coolant fan was not coming on even after about 20 minutes of normal temperature. I turned on the a/c and both fans come on. I check the fan relays and were all good. I replaced the engine coolant temperature switch as well, as still no fan. I'm thinking the fan switch is probably the last thing but before I drive a hour away to the stealership to buy the part I'd like some ideas. I'm guessing the seal was being blown to the re-circulating of hot fluid plus the parts store told me the rtv I did use was not the right kind and the fluid was probably eating away at the gasket. This time I did use the recommended high temp for the thermostat. Any opinions on a fan switch? my last resort would be hard wiring the coolant fan to the ignition so it runs when the car is running........

 

It's not a 6, but the wife's 626 had a fan go out, and researching that, I found that the fans don't come on at normal operating temps. Only when it gets higher up. Hers had a bad motor - the fans did come on normally when the AC was on.

 

If its blowing gaskets, wouldn't that suggest the system has too much pressure? Such as your radiator cap not working correctly? If its not letting the pressure out, it will build too high, and the gasket around the thermostat is most likely the weakest part of the cooling system, so it fails. May also suggest a bad head gasket, cracked head or cracked block. If compression gets pumped into the cooling system, things begin to fail. has the car ever been overheated?

Just some suggestions to consider. But I would certainly look into replacing the radiator cap.

Its possible the fan may not come on if the temp does not get high enough. Im not sure where the fan kicks on for your car, but a lot of mondern fuel injected cars are in the 210 range. So it may not ever get there at idle.

 

Yeah, i just realized today that I havent started simple with the damn radiator cap. Imma get up early and go get one. That car has been faithful as hell and runs like a champ except for that problem. Should have got a chevy! I dont think its a head gasket cause im not low on fluid ever unless the seal blew and it leaked out......atleast the 954 is super faithful!

 

I had kinda the same issue on a jeep I had once... rad cap was all it took