Odd rattling/growling noise from the engine at 5k rpm
09-19-2009, 01:26 PM
#28
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Kevin, get this sorted out yet?
Today after work i was tinkering with my car. just thought i would go over it before the long drive tomorrow. changed the oil, check the condition of the plugs, fluid levels, all that jazz. anyways, that didnt take long so i started looking for that noise again.
Ill give you a quick backstory here, so bear with me. its going somewhere.
So in the last 3 months or so we've had 3 rx8s come in on the hook. no start. not flooded. All three times, same cause. the heatshield around the cat rusts and falls off accept it cant just fall off. there is a hole in the heatshield where the rear O2 threads into the middle of the cat.
So the shield ends up hanging from these wires. Its a heafty heat shield. its not just tin. it has 2, almost 3 layers. a thicker steel inner layer, then bracing, then the tin outter layer.
So anyways, it hangs front he O2 wires when it brakes off the cat, eventually (if not immidiately) cutting through the wires. it makes connection with two of the now bare wires and you now have a short to ground or even two power wires touching. obviously this circuit is protected by a fuse, so the IG1 fuse pops. now the car wont start because the injectors wont pulse.
now this isnt a catastrophic failure or anything. the circuits involved are all protected, so you simply have to fix the damaged wires on the O2 (or worst case senario get a new one if the wires were cut too close to the sensor to fix, but this sensor is relatively cheap) and put in a new fuse and she'll fire right up.
i digress, i decided to take some preventative measures. i used 2 stainless steel hose clamps around either end of this mamoth heat shield. that sucker isnt going anywhere now. Then i though, why not hook up the front heatshield (around the manifold) the same way. so i got another stainless clamp and began tightening it down. it moved an aweful lot when i clamped it down. so i pulled it back off for inspection.
turns out the manifolds heat shield is the same insane multi layer peice found on the cat, the inner layer had come loose inside the outer tin layer. so i affixed it really well. cursing my lack of thoroughness on all my other attempts to find this noise, i took the car for a good run and have yet to hear the noise. fingers crossed, but i think its fixed. now if only i could figure out my slight lack of power issue, i'd be set. haha.
also, i might add that it is not advisable to get rid of these heatshields completely. Car manufacturers put them there for a reason. they wont spend money on redundant heat shields if the dont need to be there for good reason. I've seen the cat get litterally red hot on my own car. That much heat + parking over dry grass....no one wants to see an rx8 or someones property burn to the ground.
Today after work i was tinkering with my car. just thought i would go over it before the long drive tomorrow. changed the oil, check the condition of the plugs, fluid levels, all that jazz. anyways, that didnt take long so i started looking for that noise again.
Ill give you a quick backstory here, so bear with me. its going somewhere.
So in the last 3 months or so we've had 3 rx8s come in on the hook. no start. not flooded. All three times, same cause. the heatshield around the cat rusts and falls off accept it cant just fall off. there is a hole in the heatshield where the rear O2 threads into the middle of the cat.
So the shield ends up hanging from these wires. Its a heafty heat shield. its not just tin. it has 2, almost 3 layers. a thicker steel inner layer, then bracing, then the tin outter layer.
So anyways, it hangs front he O2 wires when it brakes off the cat, eventually (if not immidiately) cutting through the wires. it makes connection with two of the now bare wires and you now have a short to ground or even two power wires touching. obviously this circuit is protected by a fuse, so the IG1 fuse pops. now the car wont start because the injectors wont pulse.
now this isnt a catastrophic failure or anything. the circuits involved are all protected, so you simply have to fix the damaged wires on the O2 (or worst case senario get a new one if the wires were cut too close to the sensor to fix, but this sensor is relatively cheap) and put in a new fuse and she'll fire right up.
i digress, i decided to take some preventative measures. i used 2 stainless steel hose clamps around either end of this mamoth heat shield. that sucker isnt going anywhere now. Then i though, why not hook up the front heatshield (around the manifold) the same way. so i got another stainless clamp and began tightening it down. it moved an aweful lot when i clamped it down. so i pulled it back off for inspection.
turns out the manifolds heat shield is the same insane multi layer peice found on the cat, the inner layer had come loose inside the outer tin layer. so i affixed it really well. cursing my lack of thoroughness on all my other attempts to find this noise, i took the car for a good run and have yet to hear the noise. fingers crossed, but i think its fixed. now if only i could figure out my slight lack of power issue, i'd be set. haha.
also, i might add that it is not advisable to get rid of these heatshields completely. Car manufacturers put them there for a reason. they wont spend money on redundant heat shields if the dont need to be there for good reason. I've seen the cat get litterally red hot on my own car. That much heat + parking over dry grass....no one wants to see an rx8 or someones property burn to the ground.
Last edited by rotarygreg; 09-19-2009 at 01:29 PM.
09-19-2009, 05:44 PM
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Hmm Greg you raise some good points here. I'll have to go crawling around at some point to take a look.
But i dont think that is my problem... I get that noise constantly around 5500rpm... and then i topped up my engine oil (added just under 500ml to fill her up) and the noise just about completely goes away....
That's got me thinking that it could be something internal, which really scares me as its a brand new engine!
Anyways i'm going to be getting some paint work done under warranty so when it's in for that they are going to go over the engine and try to figure it out. I have to time it for when i bring out the winter beater though.
But i dont think that is my problem... I get that noise constantly around 5500rpm... and then i topped up my engine oil (added just under 500ml to fill her up) and the noise just about completely goes away....
That's got me thinking that it could be something internal, which really scares me as its a brand new engine!
Anyways i'm going to be getting some paint work done under warranty so when it's in for that they are going to go over the engine and try to figure it out. I have to time it for when i bring out the winter beater though.
09-19-2009, 05:59 PM
#30
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Damn it all! That really sucks! Thinking all is good and then suddenly......bam!
Well, I hope it's something really easy again..............let us know what it is this time.
Good Luck!
Well, I hope it's something really easy again..............let us know what it is this time.
Good Luck!
09-19-2009, 07:52 PM
#31
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****! not fixed. it took about 30mins of driving and it was back, just as before. im almost completely stumped. the only other thing i can think of for this sound im having is the SSV. it opens at 5500rpm, right about when this noise starts for me. although i dont know why or how engine temp would affect it...also, i dont really know how to tell fi this is it or not...maybe unplug the vaccuum solenoid that operates the valve and see if the noise stops....but i want to wait until after mosport to tinker haha.
06-18-2010, 07:14 PM
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Does your rattle noise sound somewhat like this?
http://www.youtube.com/watch?v=WWbtFTJMBaw
This started 2 days ago for me
hoping to find a solution...
thx!
http://www.youtube.com/watch?v=WWbtFTJMBaw
This started 2 days ago for me
hoping to find a solution...thx!
09-30-2010, 05:08 AM
#34
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I have the same problem on my RX-8.
It sound like this :
http://www.youtube.com/watch?v=h1wn8...layer_embedded
http://www.youtube.com/watch?v=BZr_l...layer_embedded
I changed coil and wire, but any effect...
Steve
Cheer from Switzerland
It sound like this :
http://www.youtube.com/watch?v=h1wn8...layer_embedded
http://www.youtube.com/watch?v=BZr_l...layer_embedded
I changed coil and wire, but any effect...
Steve
Cheer from Switzerland
09-30-2010, 06:28 AM
#35
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i forgot about this thread. i guess i should update my own findings.
I ended up putting an engine in it under warranty and that has solved the noise problem. the noise became much more appearantly and it was soon accompanied by power loss. did a compression test, all chambers and rotors under spec and max diff was under spec as well.
After the new engine, sound was gone. actually the engine sounds so different now. before, it hardly sounded like a rotary at all.
All i can think of is that the sound was created from a bad or a few bad apex seals and the sound being heard was acutally combustion popping back up through the intake. i was only able to hear it at higher revs beacuse the VFAD hides ALOT of intake noise until 5500rpm.
I used a boroscope to look inside the old engine when i had it out and there was a pretty significant build up of carbon all over the rotors so....
I ended up putting an engine in it under warranty and that has solved the noise problem. the noise became much more appearantly and it was soon accompanied by power loss. did a compression test, all chambers and rotors under spec and max diff was under spec as well.
After the new engine, sound was gone. actually the engine sounds so different now. before, it hardly sounded like a rotary at all.
All i can think of is that the sound was created from a bad or a few bad apex seals and the sound being heard was acutally combustion popping back up through the intake. i was only able to hear it at higher revs beacuse the VFAD hides ALOT of intake noise until 5500rpm.
I used a boroscope to look inside the old engine when i had it out and there was a pretty significant build up of carbon all over the rotors so....
09-30-2010, 02:31 PM
#38
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in my specific case yes.
you cant go and say if you have a "growling noise" at 5500 rpm when the car is hot and under load you need an engine.
im just reporting what happened to me. after narrowing down all other possiblities and the engine being slightly under spec for compression and vacuum voltage all that was left was the engine itself. i was very careful when taking apart to pay attention and watch for anything that wasnt tight or out of place that could cause any sort of rattle.
if my hypothesis was correct about the cause of the noise and accompanying power loss i was experiencing, then yes, a rebuild would be the fix (and in my case was the fix).
still...im not saying everyone experiencing a noise should run to their dealer wanting a free engine.
@ copper, do you notice any powerloss on long highway drives? the first time i really noticed the power loss and could say for sure 100% that i was feeling a lack of power and not just getting used to the power the car makes was on a long drive up to the rally of the tall pines in bancroft.
on one of the longer more hilly streches of highway i had the cruise on at like 120. every little hill we had to ascend, the cruise control was unable to keep speed. a slight crest would drop the speed down to around 90. i turned the cruise off and when approaching a hill went down through the gears until i was able to maintane my cruising speed of 120. that was in 3rd gear on what i would call a slight grade. and even then, the power at full throttle in 3rd gear at 120 was only enough to hold it at 120 and not actually accelerate.
i should also mention that this growling rattle noise was in full force in this situation. i stopped for a coffee break and to stretch my legs for 15 mins. when i got back in the car all the usual power was back. hills were no problem and the noise wasnt there. after about 20 mins of crusing at 120, it was back to no power and the noise was there again.
you cant go and say if you have a "growling noise" at 5500 rpm when the car is hot and under load you need an engine.
im just reporting what happened to me. after narrowing down all other possiblities and the engine being slightly under spec for compression and vacuum voltage all that was left was the engine itself. i was very careful when taking apart to pay attention and watch for anything that wasnt tight or out of place that could cause any sort of rattle.
if my hypothesis was correct about the cause of the noise and accompanying power loss i was experiencing, then yes, a rebuild would be the fix (and in my case was the fix).
still...im not saying everyone experiencing a noise should run to their dealer wanting a free engine.
@ copper, do you notice any powerloss on long highway drives? the first time i really noticed the power loss and could say for sure 100% that i was feeling a lack of power and not just getting used to the power the car makes was on a long drive up to the rally of the tall pines in bancroft.
on one of the longer more hilly streches of highway i had the cruise on at like 120. every little hill we had to ascend, the cruise control was unable to keep speed. a slight crest would drop the speed down to around 90. i turned the cruise off and when approaching a hill went down through the gears until i was able to maintane my cruising speed of 120. that was in 3rd gear on what i would call a slight grade. and even then, the power at full throttle in 3rd gear at 120 was only enough to hold it at 120 and not actually accelerate.
i should also mention that this growling rattle noise was in full force in this situation. i stopped for a coffee break and to stretch my legs for 15 mins. when i got back in the car all the usual power was back. hills were no problem and the noise wasnt there. after about 20 mins of crusing at 120, it was back to no power and the noise was there again.
Last edited by rotarygreg; 09-30-2010 at 02:39 PM.
09-30-2010, 06:24 PM
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in my specific case yes.
you cant go and say if you have a "growling noise" at 5500 rpm when the car is hot and under load you need an engine.
im just reporting what happened to me. after narrowing down all other possiblities and the engine being slightly under spec for compression and vacuum voltage all that was left was the engine itself. i was very careful when taking apart to pay attention and watch for anything that wasnt tight or out of place that could cause any sort of rattle.
if my hypothesis was correct about the cause of the noise and accompanying power loss i was experiencing, then yes, a rebuild would be the fix (and in my case was the fix).
still...im not saying everyone experiencing a noise should run to their dealer wanting a free engine.
@ copper, do you notice any powerloss on long highway drives? the first time i really noticed the power loss and could say for sure 100% that i was feeling a lack of power and not just getting used to the power the car makes was on a long drive up to the rally of the tall pines in bancroft.
on one of the longer more hilly streches of highway i had the cruise on at like 120. every little hill we had to ascend, the cruise control was unable to keep speed. a slight crest would drop the speed down to around 90. i turned the cruise off and when approaching a hill went down through the gears until i was able to maintane my cruising speed of 120. that was in 3rd gear on what i would call a slight grade. and even then, the power at full throttle in 3rd gear at 120 was only enough to hold it at 120 and not actually accelerate.
i should also mention that this growling rattle noise was in full force in this situation. i stopped for a coffee break and to stretch my legs for 15 mins. when i got back in the car all the usual power was back. hills were no problem and the noise wasnt there. after about 20 mins of crusing at 120, it was back to no power and the noise was there again.
you cant go and say if you have a "growling noise" at 5500 rpm when the car is hot and under load you need an engine.
im just reporting what happened to me. after narrowing down all other possiblities and the engine being slightly under spec for compression and vacuum voltage all that was left was the engine itself. i was very careful when taking apart to pay attention and watch for anything that wasnt tight or out of place that could cause any sort of rattle.
if my hypothesis was correct about the cause of the noise and accompanying power loss i was experiencing, then yes, a rebuild would be the fix (and in my case was the fix).
still...im not saying everyone experiencing a noise should run to their dealer wanting a free engine.
@ copper, do you notice any powerloss on long highway drives? the first time i really noticed the power loss and could say for sure 100% that i was feeling a lack of power and not just getting used to the power the car makes was on a long drive up to the rally of the tall pines in bancroft.
on one of the longer more hilly streches of highway i had the cruise on at like 120. every little hill we had to ascend, the cruise control was unable to keep speed. a slight crest would drop the speed down to around 90. i turned the cruise off and when approaching a hill went down through the gears until i was able to maintane my cruising speed of 120. that was in 3rd gear on what i would call a slight grade. and even then, the power at full throttle in 3rd gear at 120 was only enough to hold it at 120 and not actually accelerate.
i should also mention that this growling rattle noise was in full force in this situation. i stopped for a coffee break and to stretch my legs for 15 mins. when i got back in the car all the usual power was back. hills were no problem and the noise wasnt there. after about 20 mins of crusing at 120, it was back to no power and the noise was there again.
Railton
09-30-2010, 06:44 PM
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09-30-2010, 07:01 PM
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lol
09-30-2010, 09:45 PM
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Well I think I'm going to get them to run a compression test before I put her away for the winter! My engine has made this noise ever since they put it in back in June/July of last year. With no answer to date, I think it's really time to start pushing the issue!
09-30-2010, 09:58 PM
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It happened to me, it can happen to you too.
Railton
10-11-2010, 11:09 AM
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I don't know if it is of any help but I had similar symptoms with my car in early august. It made a strange rattling noise at around 5500 rpm, especially when WOT. A Mazda mechanic that I trust (a guy I went to school with) did a run with it and we narrowed the problem down to two possibilities (my engine mounts were good):
1- I had installed the Mazda hood struts in spring. Maybe something had loosened there.
2- A tank of bad gas that was causing pinging.
I always go to the same gas station (and I have been for 2 years) and never got any trouble with their 91 octane. I don't premix. I figured, since there was a long trip scheduled with the car, that I would empty as much of the tank as possible and fill it up with 94 octane from a different gas station. I did just that and I never heard that noise since then (5000km and counting).
I know that 91 is enough and that 94 costs more but to me it is worth the cost. I could return to 91 from a different gas station and probably get the same result.
So my suggestion is try a different gas station with the same octane level that you're used to (which won't cost you a cent more) or try a different octane level altogether.
Just trying to give back by helping a fellow RX-8 club member (I've been helped so much on this forum, it's amazing.)
Good luck!
Kabura
1- I had installed the Mazda hood struts in spring. Maybe something had loosened there.
2- A tank of bad gas that was causing pinging.
I always go to the same gas station (and I have been for 2 years) and never got any trouble with their 91 octane. I don't premix. I figured, since there was a long trip scheduled with the car, that I would empty as much of the tank as possible and fill it up with 94 octane from a different gas station. I did just that and I never heard that noise since then (5000km and counting).
I know that 91 is enough and that 94 costs more but to me it is worth the cost. I could return to 91 from a different gas station and probably get the same result.
So my suggestion is try a different gas station with the same octane level that you're used to (which won't cost you a cent more) or try a different octane level altogether.
Just trying to give back by helping a fellow RX-8 club member (I've been helped so much on this forum, it's amazing.)
Good luck!
Kabura
Last edited by Kabura; 10-11-2010 at 11:13 AM.
10-11-2010, 05:22 PM
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thing is i have that noise, and am dealing with mazda to get my some kinda fix...no matter what kind of gas i run..it decideds when it is going to do it, i cannot pinpoint any particular pattern at all....they first said it was ping, they have now changed thoer tune as they know that i ahve used more than one gas station in the last two years//not sure what to do