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I've had a 2018 Mazda 6 for about a year now. Last year was unseasonably warm. This year, howeve,r we've been below -30 for about a week now. Cold weather we get near -50. The second we hit the -30s the battery died and I purchased a new one, no big deal and not unusual for a 3 year-old battery. The car now starts, but is very noisy, and not just when i start it up.
Typically, any time the car is below 2000 RPM the car rumbles and is very loud, I think it's coming from the exhaust. This persists, and is not a short term thing when I first start. Driving around for an hour or more still does not stop the rumbling sound. Putting it into sport mode prevents the car from hitting those low RPMs, and as a result, seems to get rid of most the rumbling. Has anyone experienced this? I thought the loud Mazda exhaust was only supposed to occur when you first start the vehicle.
 

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Everything makes noise when it's that cold. Got any snoe/slush built up under the car or in the wheel wells? It's solid ice, now.

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When Mazda’s are first started they go into a “warmup” mode, that’s when the blue temp light is on and the rpms are higher. It does this so the car gets warmer faster so as to reduce emissions. Thus makes the car noticeably louder and the “warmup” doesn’t stop until the ecu sees the coolant temp get around 140-150F. That could definitely take a little bit in temps that cold. If the blue light stays on for a long time even while you’re driving I would stop at your local dealer, there is an issue with certain models here in the us related to the cooling system having constant flow which keeps the engine too cold. I would also make sure all the fluids are at good levels and the correct fluids are being used.
 

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Discussion Starter · #4 ·
When Mazda’s are first started they go into a “warmup” mode, that’s when the blue temp light is on and the rpms are higher. It does this so the car gets warmer faster so as to reduce emissions. Thus makes the car noticeably louder and the “warmup” doesn’t stop until the ecu sees the coolant temp get around 140-150F. That could definitely take a little bit in temps that cold. If the blue light stays on for a long time even while you’re driving I would stop at your local dealer, there is an issue with certain models here in the us related to the cooling system having constant flow which keeps the engine too cold. I would also make sure all the fluids are at good levels and the correct fluids are being used.
Thanks. There is no blue light that comes on. I'll check with her dealer. Asuming my gauges are in C here, the issue persists far beyond 140F. My car gets to 100C in 15 min or so.
 

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Thanks. There is no blue light that comes on. I'll check with her dealer. Asuming my gauges are in C here, the issue persists far beyond 140F. My car gets to 100C in 15 min or so.
Another thing to check would be the gasket between the exhaust pipe flange and the muffler flange. I see a decent amount of older cx-5s and other models with that issue after about 70k miles those start to degrade leaving a bunch of blackness built up on the flange and you'll see water droplets forming there more than coming out of the actual muffler tips. Losing this gasket usually does create a bit more of a rumble than normal but being a newer model I doubt that's the issue.
 
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