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Firstly, please don't immediately click away because I wrote a novel. ᵖˡᶻ ʰᵉˡᵖ

I have a 2.5L 2010 Mazda 6 with 73k miles.

1. It's developed a mystery dull grinding noise at ONLY at 2000-2100rpm, fluids are all good. Happens in all gears including park so I doubt it's the transmission. Loudest in 5th on the highway when holding at 2100rpm. The fact that it occasionally doesn't make the noise leads me to suspect it's a vibration.

2. When am I supposed to get a transmission flush? I'm at 73k and have no idea if it has been done by previous owner. The manual says nothing about it, just about checking the level. It's slightly bronze colored with some particulate, should I do a drain and fill or a proper flush (I've heard that both are the wrong answer lol)?

3. Both of my 'original' low beams went out one at a time. I had an LED kit put in and they both worked fine, but THE VERY NEXT DAY the passenger one went out. I've heard smacking the cover can make it come back but that doesn't do anything for me. I doubt it is the fuse considering replacing the bulbs initially worked. I haven't been able to look at the harness myself to check for burns but the shop did not mention anything. The LEDs draw much less power so I have a hard time blaming poor grounding as many do.

Might be relevant but I have a subwoofer regularly drawing about 1500w RMS and two batteries (One AGM, one acid) totaling about 2200 CCA with stock 110A alternator. Voltage never goes bellow 12.5v but I usually keep it around 13.2v when the sub is hitting (14v Idle in winter, in the warm it idles at 13.3v for some reason??).

I have never had any issue with my high beams so I have a hard time blaming the subwoofer. My gut instinct tells me it's a grounding issue, but why would the new LEDs work for a short period then, especially considering how much less power they draw? I will poke around to see if there's any obvious breaks or melting tonight.


I appreciate any advice and don't expect anyone to magically know the solution as more information is probably needed. Overall I love this car and have put 12k on it with minimal issues despite beating the living shit out the electrical system. Would love to become a more active member of the forum in the future.
 

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For the grinding sound, just taking a wild guess, might be a wheel bearing? In a better case scenario, it could possibly be a loose heat shield underneath. Is it hanging anywhere?

I had a '10 like this for a few years and it was a lovely car, but I found that the low beams went out much more often than other cars. I'm not sure why and I can't offer any advice for your current problem.

For the transmission flush, the miles aren't extremely high but it's a 10+ year old car at this point so it would be worth doing. I think you'll find most here would recommend not a flush but a drain and fill since flushes can be too invasive.
 

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Rally Racer
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Welcome to the forum.


Firstly, please don't immediately click away because I wrote a novel. ᵖˡᶻ ʰᵉˡᵖ

I have a 2.5L 2010 Mazda 6 with 73k miles.

1. It's developed a mystery dull grinding noise at ONLY at 2000-2100rpm, fluids are all good. Happens in all gears including park so I doubt it's the transmission. Loudest in 5th on the highway when holding at 2100rpm. The fact that it occasionally doesn't make the noise leads me to suspect it's a vibration.[\QUOTE]

This sounds like an engine rotation thing. Sitting parked with the motor revving at 2000RPM makes the sound?


2. When am I supposed to get a transmission flush? I'm at 73k and have no idea if it has been done by previous owner. The manual says nothing about it, just about checking the level. It's slightly bronze colored with some particulate, should I do a drain and fill or a proper flush (I've heard that both are the wrong answer lol)?[\QUOTE]

I would drain and refill now a couple times


3. Both of my 'original' low beams went out one at a time. I had an LED kit put in and they both worked fine, but THE VERY NEXT DAY the passenger one went out. I've heard smacking the cover can make it come back but that doesn't do anything for me. I doubt it is the fuse considering replacing the bulbs initially worked. I haven't been able to look at the harness myself to check for burns but the shop did not mention anything. The LEDs draw much less power so I have a hard time blaming poor grounding as many do.[\QUOTE]

LED ballasts can be very finicky with power supply. Were they wired through a relay directly to the battery? If they are on the vehicle wiring I would suspect suspect. The OE wiring should be used as a trigger only, especially with all that electrical nonsense you have going on back there.


Might be relevant but I have a subwoofer regularly drawing about 1500w RMS and two batteries (One AGM, one acid) totaling about 2200 CCA with stock 110A alternator. Voltage never goes bellow 12.5v but I usually keep it around 13.2v when the sub is hitting (14v Idle in winter, in the warm it idles at 13.3v for some reason??).

I have never had any issue with my high beams so I have a hard time blaming the subwoofer. My gut instinct tells me it's a grounding issue, but why would the new LEDs work for a short period then, especially considering how much less power they draw? I will poke around to see if there's any obvious breaks or melting tonight.[\QUOTE]

You likely never had an issue before becuase they were halogen. So when you say that you keep it at 13.2 when your "sub is hitting" does this mean you keep the accelerator pressed at idle?

I appreciate any advice and don't expect anyone to magically know the solution as more information is probably needed. Overall I love this car and have put 12k on it with minimal issues despite beating the living shit out the electrical system. Would love to become a more active member of the forum in the future.
[\QUOTE]

It's the comment about the electrical system that seals the deal here I believe. In my opinion the electrical on this Mk1 Mazda6 is pretty delicate. Between crumbling connectors, shoddy grounds and moody controllers it is a science experiment in the running keeping the thing error free.

Test to make sure the ballast is getting power with the headlights and replace them if they are getting power but not working. I fried one of mine with my electrical shenanigans last year. They are pretty cheap. Good Luck.
 
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