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04 Mazda 6 Sport Wagon 5 Speed Manual
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Discussion Starter · #1 · (Edited)
Hello all,

You please tell me if I’m just being paranoid.

My 6 has has a very subtle tick or knock which is really only noticeable at idle. I first noticed it about a year ago but could have been there when I bought it months prior. This sound has not worsened for the past year and I figured out to be normal for a car with over 200K.

The last couple of days I’ve noticed something a bit different. The change is hard to notice but I am very in tune and sensitive to any changes in the sound or feel of my engine. The new sound is kind of like an added puttering to the usual sound of my engine. Noticeable most between 1000 and 2500rpm. This has lead me to take another close listen to my engine. This new sound could be related to the original knock Ive had since a year ago or it could be something new entirely.

The new issue is hard to describe but I will do my best. My engine makes a whine or whistle at around 2500RPM which is normal, just the sound of all the belts, chain, gears, and what not at that particular speed. This new puttering or roughness I’m getting is now “imposed” itself upon this usual whistle. Think about how it sounds like when you whilste vs when you then whistle into a fan.

Again important to note that this is all very subtle, but I notice it and am trying to prevent anything from growing into a bigger problem.

Today I listened up close under the hood and found that my 1 year old knock or tap seems to come from under the plenum on the windshield side of the engine compartment. It doesn’t seem to be as audible from the bottom of the engine but I haven’t crawled under the car to really get up close and personal with the engine. It begins to be noticeable after warm up.

Additionally I found a new sound that sounds like a pair of scissors snipping really fast. This new scissor sound may be more related to my new engine roughness than the original knock sound but who knows. This sound also comes from somewhere around the plenum. The scissor sound comes and goes at random.

Attached is an audio clip. From the beginning of the clip to around the 12 second mark is when you can most hear the knocking sound I’ve had for about a year. Immediately after that you hear the new snipping sound come in for a moment. From about 1:05 you can hear the snipping type sound which then abruptly stops at 1:23.


Do any of you guys recognize either of these sounds? I’m hoping my knocking sound is just something stupid like a lifter or lash adjustment and not an early sign of rodknock. The sound was recorded with my phone literally touching the plenum. At other times I was moving around the engine compartment trying to find the best spot. The knocking sound is most noticeable with the hood open or from inside the cab.
 

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2005 6S wagon 5MT
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139 Posts
Maybe I'm missing something but that all sounds normal to me. The noise at the beginning just sounds like injectors, mine is pretty much exactly the same.

Oil level good? What's your mileage?

Not sure about the second noise you describe, but I would seriously doubt anything catastrophic is imminent. Maybe a slight exhaust leak opening up? These engines seem prone to having the stud right above the alternator in back break off. I'd think that would make your sound more pronounced when it's cold, though. Or maybe a belt tensioner or idler getting a little loosey goosey? Mine were pretty roached at 135k.
 

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04 Mazda 6 Sport Wagon 5 Speed Manual
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Discussion Starter · #3 · (Edited)
Hello,

Yes oil level is good. Mileage is somewhere over 220K.

It could be an exhaust leak. When I start the car from dead cold I have a ticking that goes away after about 30 seconds of run time. I think that might be an exhaust leak as I can kind of smell raw exhaust in engine compartment at start up. Could also be a bad lifter. It’s had it since I’ve owned it.

This new puttering that is happening which is bothering is most noticeable from inside the cab. In the engine compartment it kinda gets drowned out by all the other noises the engine makes.

Here is a clip of the sound from inside the cab with the phone held up to the heater vent and also in the second half of the clip with the phone held up underneath the dashboard.

This is with me holding the engine around 1000-1500rpm where I notice it most. Try using headphones. It’s a bassy sound.


It almost sounds like a misfire to me but I don’t have any codes.
 

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2005 6S wagon 5MT
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139 Posts
Hello,

Yes oil level is good. Mileage is somewhere over 220K.

It could be an exhaust leak. When I start the car from dead cold I have a ticking that goes away after about 30 seconds of run time. I think that might be an exhaust leak as I can kind of smell raw exhaust in engine compartment at start up. Could also be a bad lifter. It’s had it since I’ve owned it.

This new puttering that is happening which is bothering is most noticeable from inside the cab. In the engine compartment it kinda gets drowned out by all the other noises the engine makes.

Here is a clip of the sound from inside the cab with the phone held up to the heater vent and also in the second half of the clip with the phone held up underneath the dashboard.

This is with me holding the engine around 1000-1500rpm where I notice it most. Try using headphones. It’s a bassy sound.


It almost sounds like a misfire to me but I don’t have any codes.
These cars don't throw a code unless you have a pretty bad misfire. How fresh are your coils/plugs? Are you having any hesitation when accelerating?

I can hear what you're talking about, but it doesn't sound alarming to me. Does it get worse when the engine has load, like accelerating up a hill?

I wonder if your motor/trans mounts are getting tired and transmitting more noise into the cabin. I have AWR polyurethane mounts on mine and they really bring all the transmission gear noise into the cabin. If you didn't know better you'd think the engine was about to come apart.
 

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04 Mazda 6 Sport Wagon 5 Speed Manual
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Discussion Starter · #5 ·
I actually have no idea about the coils and plugs. I’ve never changed them since I got the car. I’ve been meaning to replace them. I hope I get a good weekend before winter so I can get that done. Would love to also replace the injectors but they’re expensive. Do you know if they’re worth buying OEM rebuilt and any good rebuilders? Or any good sources in general for injectors? What about for coils and plugs?

Yes! It could be a bad engine mount. I know I have tired dog bone mount and this noise started after getting home during a trip where I kinda did a bad shift and the car jerked. The engine otherwise sounds fine and I don’t notice any change in performance nor does it hesitate.

Ive read that for engine mounts it’s best to go OEM. However I do see some people recommending me mounts such as yours but I don’t know if that’s worth it for me as I’m not doing anything performance and would rather keep the noise down. The OEM ones are about 150 vs the 50ish dollars for the auto zone ones.
 

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2005 6S wagon 5MT
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There are cheaper coil sets on Amazon, but probably best to go with an OE manufacturer. I put Denso DAC673-6005 coils on mine and they have worked out just fine. I think for plugs people usually do Motorcraft or NGK Iridums. I got Motorcraft SP-479s. Just gotta make sure they're gapped properly.

Not sure if it's worth replacing the injectors if they're currently working. The main concern with misfires caused by coils/plugs is raw fuel fouling the cats, which is unfortunately a common tale of woe with these cars.

I'd agree that OEM mounts are best. I got the cheap ones for my old Accord and they blew out pretty quickly. That said, there's nothing really complicated about a dog bone mount. The fluid-filled ones are where you run into problems with aftermarket.

The 'performance' mounts are probably also not worth the cost. They've tightened up shifting a bit but not in a way I'd call dramatic.
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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I think it sounds mostly okay. I am with @Ignatius Reilly with the plugs and coils but I am super sensitized to this.

DENSO 673 6005 - Ignition Coils x6
Mazda AJTT-18-110 - Spark Plugs x6 (these will be Motorcraft AGSF 22FSCM) Motorcraft SP-479

The comment you make about smelling "raw exhaust" makes me think that maybe a spark plug has worked itself loose. It can both account for a "new sound" that is "like a misfire" and also smells "raw". The 6-cyl is also plagued with a propensity to break the exhaust stud directly above the alternator. It will often leak from there especially when cold (conveniently sucking it into the cabin fresh draw). That sound is more like a snap though and smells strong but not "raw". Grab a flashlight and see if it is sitting on the alternator.

If you don't know the history of the ignition, I would strongly recommend replacing the plugs (platinum or better) and the coils (all 6). Do the PCV valve while you are there (upgrade to the non-collapsing hose if you still have the old style).
I would not mess with the injectors at all unless you had a known failure.

I did all my motor mounts and have to do the "dog bone" periodically. I had to go with OEM for both the trans (difficult to find for my 5-speed ATX) and passenger but don't spring the extra for the dog bone because it does not last either way.
 

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04 Mazda 6 Sport Wagon 5 Speed Manual
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Discussion Starter · #8 ·
Hello guys,

I ordered the dog bone OEM and received it today. Wish I’d seen your comment about not bothering for OEM on this part Dr Feel Good. I’m actually wondering if the part I got is even OEM. The only packaging or labeling is as shown below.

BTW I kinda used the wrong words to describe the exhaust smell under the hood on start up. What I meant by raw exhaust is that it smells like exhaust not having gone through the catalytic converter. I’m not sure if that’s really the smell but that’s how I remember old car exhausts smelling where as my cars normal exhaust has a different flavor. Lol

So far not noticing anything worse. I’ll install the dog bone over the weekend and report back. I also had my clutch stick about half way at a stop the other day until I lifted it with my foot. It didn’t take much effort to return it and it has only happened twice since I’ve had the car but it may be the sign of bad mounts.

Here is a picture of the part. Does it look OEM? Kinda feel like returning it and saving the money for OEM trans and passenger mounts.

Wood Font Audio equipment Circle Electrical wiring
 

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04 Mazda 6 Sport Wagon 5 Speed Manual
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Discussion Starter · #9 ·
Hello guys, I changed the dog bone mount and though it helped get rid of some of the cab noise I was having, that weird ticking sound is still there and getting worse. The other day after accelerating sort of hard out if a parking lot I noticed an increase in the noise right after. It’s been that way since though sometimes it seems intermittent.

Below you can listen to two separate clips.

The first clip is at idle and the second clip is from inside the cab with me holding the RPM at 1500 RPM where it’s most obvious. Above 2000 I don’t really notice anything.




The dog bone mount was very destroyed and the engine was moving around a lot. Replacing the dog bone mount cured a clutch chatter I had when taking off below 2k RPMs or so. I had to up my clutch game to avoid it chattering and now I can drive normal. I’m hoping this could be an exhaust leak or one of the rusted pieces of metal around the exhaust manifold. I did an oil change yesterday and found no signs of shredded metal. It may be that the filter caught them though if that’s the case. This also has been happening since I bought cheap gas at another gas station, perhaps an octane issue? I’ll have to pour in some at the place I usually buy gas. Just really hope it’s nothing major.

Plugs and coils after I try and see if there’s anything easier.
 

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2005 6S wagon 5MT
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Maybe cut the oil filter open to see if there's anything shiny in there?

I know you just did an oil change, but when it's time again, I'd send a sample to Blackstone labs. They send you a detailed report on the metal/coolant/etc. contents of the oil. Last time I checked it was $25. They send you all the materials you need and it's super easy.

You could also try a heavier weight oil. If that affects the noise, then you know it's something internal.
 

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04 Mazda 6 Sport Wagon 5 Speed Manual
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Discussion Starter · #11 · (Edited)
Thanks,

I wish I'd known about the lab test sooner! I actually still have the burnt oil but it's mixed in with the stuff from last oil change which has been sitting for a year.

I should have mentioned that when I did my oil change I switched to Valvoline full synthetic high mileage oil, previously I was using Valvoline synthetic blend high mileage. I'm hoping this is a reason for my increase in noise and that this could be lifter related.

I did more snooping around today and I'm pretty convinced the sound is actually coming from cylinder #4. That is, assuming I have the firing order correct. From left to right 123 right infront of windshield and 456 towards the radiator correct? Using the screw driver stethoscope the sound definitely seems to me like it's mostly located on cylinder 4, the one next to the power steering pump. Unplugging the coils on cylinders 4, 5, and 6 they all seem to make the noise disappear but I think it's most effective when unplugging 4 and 5.

I can also hear the noise coming from the bottom of the oil pain which worries me but I THINK it is most concentrated near the top of the engine under the valve cover. I am further encouraged that it is closer to the top of the engine because when I place my screw driver stethoscope into the valley of the engine I don't really hear the noise that much. I took the coil out and put my screw driver right on the spark plug and like this I couldn't hear the noise except for maybe a very subtle remainder of it.

As I've mentioned previously the sound isn't really there under load. I've even tried to bog the engine by taking off with the clutch and no throttle, taking off in high gears, and taking off with the hand brake on, all to try and load the engine but I don't really notice the noise in these instances. I would expect if this were rod knock or piston slap for the noise to become worse in this condition or to become loud when revving which also doesn't happen. It's always most noticeable at idle and between 1500-2000 RPM.

Furthermore I've noticed that this sound can vary. Sometimes it's a little more intense than others.

If this turns out to be the worst case scenario of a bad rod or piston slap, what repair options are there? Is this a whole engine swap? Is it repairable by just replacing what's bad? I'm in the Chicago area so I have no idea how much it would cost to have it done, not to mention winter is here!

Here is the latest clip I managed to record of this stupid sound, this one was taken by holding the phone right up next to the coil back of cylinder #4. This exaggerates how loud the sound is but it would otherwise be hard to capture.


I'd hate to have something major happen to my car. I LOVE MY WAGON!!


PS. I'll be replacing the valve cover gaskets when I open this up. Should I use RTV along with the gaskets or just the gaskets themselves? Thank you.
 

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2005 6S wagon 5MT
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Use a little RTV where the gasket meets the timing cover, as well as where it meets the water pump housing (for the front cover).

As for the noise, I'd still wait and see (and do an oil analysis at next oil change) but maybe have a contingency plan in case the poo crosses the fan, as these engines do go boom once in a while. This V6 is common and cheap enough that I wouldn't mess around with fixing anything internal, just pull it and swap in a new one. The first-gen Ford Fusion/Mercury Milan engine is exactly the same, barring a few things like timing/valve cover/oil pan and WAY cheaper than seeking out a bespoke 6 block. This guide has everything that you'd need if it comes to that.

I'm with you on the wagon, I've only had mine a little over a year but I adore it. Even in the worst case scenario, it's fixable and IMO worth keeping these guys on the road.
 

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2004 Mazda 6s Wagon ATX
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Hello guys,

I ordered the dog bone OEM and received it today. Wish I’d seen your comment about not bothering for OEM on this part Dr Feel Good. I’m actually wondering if the part I got is even OEM. The only packaging or labeling is as shown below.

BTW I kinda used the wrong words to describe the exhaust smell under the hood on start up. What I meant by raw exhaust is that it smells like exhaust not having gone through the catalytic converter. I’m not sure if that’s really the smell but that’s how I remember old car exhausts smelling where as my cars normal exhaust has a different flavor. Lol

So far not noticing anything worse. I’ll install the dog bone over the weekend and report back. I also had my clutch stick about half way at a stop the other day until I lifted it with my foot. It didn’t take much effort to return it and it has only happened twice since I’ve had the car but it may be the sign of bad mounts.

Here is a picture of the part. Does it look OEM? Kinda feel like returning it and saving the money for OEM trans and passenger mounts.

View attachment 244317
Sorry I missed this. Put an @ in front of my username and it will ping me right away.
That mount look like the one. I have seen variation between the manual and auto trans. Both fit fine but the gaps between the rubber vary. I decided to go with a modified lower mount. I did not want one of the high durometer ones because I drive an automatic 🙄 and would be driven crazy by the increased vibration at stopped idle. I wanted the compliance of rubber with extra strength.

I replaced my 3rd "dog bone" last weekend. even in the auto they always tear. I finally decided to modify it. See below.
Automotive tire Bicycle part Household hardware Gas Rim


The part is an Anchor 9221 from Amazon and the gaps are filled with a 3M product designed for installing windshields.

Your description of "raw smell" for me is a bit of the odor of gasoline, sitting in a cup, with a non-emissions exhaust nose. (A bit of automotive terroir.) I grew up driving carbureted cars and still have the dual side-draft specimen so I am familiar with both.
The un-catalyzed exhaust in the 6v is probably coming from a broken manifold bolt up above the alternator as said above. The "snap" sound in your audio (on second listen with headphones) sounded like mine. Take a flashlight and look behind your motor to the top of your alternator. I have seen studs, several times, sitting on it when browsing the salvage yards. That right rear corner is a perfect position for being pulled into the cabin my the fresh air draw under the windshield. See pic below.


Automotive tire Motor vehicle Automotive wheel system Gas Auto part


Cheers.
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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@DrFeelGood is correct, I had the same snapped stud and have also seen it on other Duratec 6s in the junkyard. It's real fun to drill out, as I know he can attest to.
Haha, mine took 20hrs to extract, given I could not see it, since it was toward the firewall and below the surface of the head. It also broke on a steep angle so the drill bit wanted to walk into the aluminum head which it penetrated like warm butter. I did manage to save 96% of the original threads however taking my time. Drill a tiny bit, take a pic, drill a bit more, take a pic, repeat for 168pics...
Another user on here, was it you @Ignatius Reilly ? (guessing not based on your comment), had it break just above the manifold mating surface and could grab it with locking pliers. YMMV.
Good luck
 

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Another user on here, was it you @Ignatius Reilly ? (guessing not based on your comment), had it break just above the manifold mating surface and could grab it with locking pliers. YMMV.
Good luck
Nah, I wasn't that lucky. Luckier than you though!

Mine was broken off just under the surface of the head, but mostly flat. Took about two hours of careful drilling and was able to extract the stud with an easy-out.
 

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04 Mazda 6 Sport Wagon 5 Speed Manual
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Discussion Starter · #17 · (Edited)
@DrFeelGood thanks for making yourself accessible! Thanks to both of you for all the continued support! @Ignatius Reilly

I've been babying the car the past few weeks as I figure out a way to fix this issue. Here in Chicago the winters are a major draw back as even working on your car becomes impossible for half of the year. I'm not sure if it's any the same where you are. I'll be checking into the exhaust leak. If it's that then I may even just leave it like that for now.

I'll be taking the car to a shop just to avoid myself the cold and the hassle. If the shop finds something internal that can still be fixed reliably then I'll take that option. It may be a band aid fix but if it can get me past winter then I'll be happy. In the meantime I'll try and cultivate some other options.

A fusion swap fix presents a bit of a dilemma for me. I'd love to do it myself but it's honestly more than I can chew. Especially considering it's my daily driver, I'm under equipped, and everything is rusty from the Chicago winters. On the other hand paying a shop to do all the necessary fusion adaptations would add a lot of cost to the already pricey process of doing an engine swap. Shops may offer to do a mazda to mazda swap however this is also additionally expensive as these engines cost more when they come out of another 6. Haven't seen many guys pay to have this done either. Only you crazy guys getting dirty and doing it yourself. I get the feeling me asking a shop to do this fusion swap thing for me would get me a lot of eyes rolling from mechanics. I haven't ever had experience having something like this done on my car. Any advice?

As I said I'm hoping for a reliable fix if it is an internal engine. My engine is definitely up in the miles. The longer I can keep it going the more chance I have to figure out my alternatives.
 

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Rally Racer
2004 Mazda 6s Wagon ATX
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@DrFeelGood
[..snip]
As I said I'm hoping for a reliable fix if it is an internal engine. My engine is definitely up in the miles. The longer I can keep it going the more chance I have to figure out my alternatives.
I am strongly suspecting it is the exhaust and does not pose a serious problem (other than toxic inhalation) for the winter. I live in the PNW and pulling another warm car into the garage and/or a small space heater is all I need to work, at any point in the "winter". No rust because we don't salt (well, not until last year that is).

If for some reason you need a motor swap I would look outside of a shop. In my area and in my community I can find someone who will often do that work from their home. We asked the guy that does the landscaping next door and he had a friend that put a new (used) transmission my neighbors F150 for $400 (plus $400 for trans). He picked it up from the house , changed it, and dropped it off when done. That same neighbor, through the same yard care people, found a Russian guy to swap the motor in his Volvo XC70 for $500. Neither could speak very good English but they spoke the language of machines quite well and could work without expensive shop overhead.


Grab your cell phone, turn on the flash, and slide it back behind the motor on the passenger side. Take a few pics and it should be quite easy to see if the stud in question (circled in red) is still there.
Human body Jaw Motor vehicle Wood Automotive tire


Good luck.
 
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