SpoonMcForky

I'm going to try to give as much detail as possible here.
2005 RX8 Base
Issue:
Strange scraping/grinding/popping sound coming from front passenger side. A sound clip of the noise is attached, taken from the floor of the passenger side. It started happening, or at least became loud enough for me to notice after I had taken the car through a car wash. Something to note which may just be coincidence, but every time I've gone through this particular wash, the entire wash shuts down for a few second. Anyways, as I was driving away I started hearing this sound. I rolled down my window and could hear it outside as well.
It's definitely gotten worse since I originally noticed it. It happens at a few specific times, almost always in mid range if I give more than 25% throttle, sometimes it happens when starting from a stop, but I've also gone from 1000-9500rpm full throttle without hearing it. Other times it just seems to happen randomly. Doesn't happen when going over bumps, did a pretty harsh clutch dump to see if it was with stress in the drive train but I didn't hear it then either.
Some "symptoms" are

• Loud engine breaking when above 5k rpm. Very strange bassey sound, almost like resonance, that comes from the front of the car.
• Car sounds deeper in general

This is a New York car, so right now my oil, at least in the dipstick area is extremely foamy, I know this is normal but thought I'd share. Oil light comes on periodically but I've also heard that it's somewhat normal for air to get in the sensor. Overall I don't feel like there's a loss of power. It also sounds quite normal when doing neutral or clutch out revs. Something else to note: I did drive the car pretty hard a few days before I took it to the car wash, and between that time I hadn't driven it because we got a lot of snow and I'm not very versed in driving RWD in the snow. I put it up on a lift checking for anything that might be lose, exhaust leaks, etc. but didn't see anything.
Things I thought it could be.

1. Catalytic Converter: My first guess. Since it sounded like something was scraping against the road, mixed with a change in engine sound I thought it could be a bad cat.
2. Exhaust Leak: Thought that maybe a small exhaust leak could cause this sound.
3. Transmission: Since it sounds like grinding, could be something in the trans
4. Wheel Bearing: Slight vibration over ~65mph. I checked the bearings on a lift and they seemed alright, but I've also read on this forum that the same issue can occur and doing the normal wheel bearing check by just twisting left-right up-down doesn't always show it.

Loki

iTrader: (1)

Does it sound like MIAC? https://www.rx8club.com/rx-8-discuss...n-miac-181950/

Can you narrow down if the sound changes with engine speed, wheel speed or neither? That'll point to which component is making the noise.

Do you feel the sound through the seat or through the shifter? Suspension problems tend to resonate through the structure, while engine/trans core issues come through the shifter, which isn't insulated by engine mounts (which, by the way, are good ro check for failure). If it's neither of the above, then it's more likely a non-structural component like heater core, exhaust, etc.

SpoonMcForky

It's more like a distinct metal on metal (or what I originally thought to be metal on asphalt) sound. I don't think I've ever heard a change in the sound at different speeds or rpm, sounds the same pretty much always. I can take it for a drive and listen for any changes and see if I can feel it through the shifter.

SpoonMcForky

Don't feel anything through the shifter, and I don't really feel anything at all. I noticed that it is happening when off throttle as well. Did a few WOT pulls, didn't hear it at all, just putt-ing around I hear it all the time. I started to think that it could be rocks or something else in my heat shield, as mentioned by a lot of other people who describe some of the same things, but I don't hear it when going over bumps. I also think that I may have heard a similar sound when stationary in my driveway, in neutral and letting off the footbrake. As soon as it starts to roll I'd hear the same type of sound, just not as loud and not as fast.

Loki

iTrader: (1)

Does the sound stop if you apply the brakes, however lightly?

SpoonMcForky

Don't know, I'll have to test that tomorrow.

Also congrats on 6969 posts :D

dannobre

iTrader: (3)

Jack up the front right and check the wheel bearing and the brake....