bhammer

2009 GT m/t

All, I have noticed over the last two days that I get a very strange, almost a rattle noise, but only when it is really wet outside. For example, yesterday, I noticed it after about 15 minutes while headed to work. Then, headed out for lunch, I didn't notice it all all. The rain had stopped at this point for a bit. then headed home, I get the same noise. Same thing today. Once the car dries, no noise. Here in DFW, we have had very heavy rains and the roads are soaked.

The Noise: It is like a sheet metal ratlle in the exhaust when at idle. I think it is most pronounced around the shifter. Just above idle at a stand still, the sounds goes away. When driving at 25+, the groan of the engine is much more loud with a deeper tone to it. This comes in any gear.

Again, I know this sounds crazy but it only seems to happen when there is a lot of water on the roads. I have attached a zipped sound clip.

Any thoughts. My dealer is not know for their RX8 work....

jasonrxeight

thats very weird.

bhammer

That it is. I confirmed that the noise is gone but it hasn't rained in a couple days.

VashGS

Hum is your ac draining and also rain drain? To check after ac has been run more than 10-15 mins and you should see dripping from around the transmission housing area. Also pour water from garden hose into hood grill and see if all drip out on bottom too. If the "duck bill" AC drain is clogged put hand over oil filter and in middle above towards transmission is nipple "duck bill". Massage it a bit lol like you want some milkz and that unclogged mine. Good luck I think it's same on 09 as series 1.

bhammer

Interesting, I found an old thread about this issue when I was searching for something else. https://www.rx8club.com/rx-8-discussion-3/heavy-rain-%3D-loud-exhaust-154869/#post4139174

I had the car at the dealer the other week and they couldn't find or fix the problem....

Digger1911

Wow, will done on the MP3 file, I have heard a similar rattle. However not quite that deep in tone.

Couple of questions.. is the (noise) many coming from the right side of the car? (passenger side)
If you open the glove box, does the sound change at all? Does the rattle become louder?
Is the A/C compressor on, defogging the windshield?

bhammer

It is very strange... Drives me nuts. In the other thread, he was talking about it sounding like a truck was next to him. It really is when you are going 60 down the highway. When I first heard it, I kept trying to find the harley with straight pipes.

It sounds like it comes from dead center of the car as each seat sounds the same. I've tried with ac on and off and the radio on and off. I don't know about the blove box but, I have had the orfice installed if that is what you are talking about.
When I popped the hood a couple months ago, it sounds like it is from under the car, just behind the firewall. Now, I am just trying to time a good rain storm with the dealer being open so they can hear it.

Speed_8

1000th post yey me ...... maybe you have a lose heat shield and when it rains the water is hitting it... not really sure.

Digger1911

orfice installed?? What orfice? 90% of the time a rattle is caused by the last guy under the hood, Or dash. What has been worked on just before this all started?

Check the under engine cover, all bolts and pressure tabs are present and tight. using a garden hose, run water on top of cover.
Does the cover sag in the middle?

Check all AC hoses straps, Lets rule the AC hoses out. attach a bungie cord to one of the ac hoses, NOT to tight, just enough to change or control the rattle. If there is no change, then next. With glove box open and cabin filter removed, What do you hear?? The ac heater air plenum will like a speaker.

bhammer

Orfice installed to resolve the rattle noise (marbels in can sound) of the coolant turbantly running through the heater core at high rmp levels. I had the engine cover off and it was still there. The only work done on the car was have the 2nd/3rd gear syncro changed in the transmission. Unfortunatley, I heard this noise prior to this.

Good ideas on the hoses. I'll do that and when it's forcast to rain, I'll pull the pollen filter out.

Thanks for the ideas.

Digger1911

Under, centre of car.. When it is rattling what happens if you...
1) push in the clutch padel and release, any change?
2) push in clutch and shift to reverse, ?
3)and than 6th gear, anything?

Rules out trans, next.

bhammer

Thanks,
1, 2 & 3 all tried. I even tried 1-5 with the exact same results.

I have to take my boy to his Cub Scouts meeting. I'lll be back in several hours. Keep it comming guys.....

Digger1911

Does it sound like this? Exhaust rattle or broken cat?

bhammer

No it doesn't. It has a little more pitch to it and closer frequency. And, that rattle only happens when I am idol, or moving and depress the clutch and play with the idol between 1000 and 1500, only after driving through water. What was the casue of this? I'm always open to take a look.

Digger1911

I understand it is rain, temperature dependant. I won't send you on a goose chase on purpose.
With that being said, lets rule out the exhaust. Then the engine mounts. You state that it only happens at idle, or when there
is No load on the engine.
That leads me to believe one of the mounts might be collapsed allowing the exhaust to come in contact with something.

few more Q's ... When the noise, rattle is present, what happens if you put tension on the exhaust system. (Similar to the AC hose test)
Any change?
Using a long screw driver,or 1/4 extension, or whatever you have, hold one end against the exhaust and the other next to your ear.
What do you hear? any Rattling?
With the engine off, use a rubber mallet and tap on the cat, should sound solid.

bhammer

Thank you for the help!! The rattle only is no load / idle but the deep groan happens at all speeds and rpm / load ranges.

I'll give the exhaust a good run through the next time it happens. I have some ramps that I plan to put in my trunck so I can get under the car as well.

I have a stephascope that I used the last time around and couldn't pinpoint to anything close but couldn't access underneath.

Great thoughts and ideas. Thanks....

ASH8

Yep, that is a good idea..

To me it sounds like an exhaust rattle or knocking...

So any of the obvious, have you done ANY mods on car, or any by another owner?

But yes, up on a hoist with a rubber mallet gently hitting exhaust area when HOT and Cold?

bhammer

I would agree that it is some kind of exhaust rattle. The only mods I have done was add thermal insulation to the cup heaters to make them cup holders. I'm in the planning stages of replacing the entire Bose system but haven't done anything yet. I am the original owner.

I think the next step is to get it on a lift and see if there is anything now and then again when it makes the noise when it storms outside.