So I was driving my rx8 around yesterday totally fine, no issues whatsoever. now today I noticed a hard to describe sound when in 2nd gear, it sounds like someone sucked up a bunch of bb’s into a vacuum cleaner lol. Here’s a video showing the sound. Maybe low transmission fluid?

 

Does it only happen under acceleration? Look up "marbles in a can" sound.

 

oh wow didn’t know this was a common-ish issue. It was just odd to me since it only happened when I shifted to 2nd gear. I let the car cool down and I started it up again an hour or two later and the sound was almost completely gone. My guess is it’s the heater core making that sound then since it’s coming from around there. My coolant is a tad bit on the low side so I’ll try topping it up and going from there.

 

If that’s indeed that’s your heater core, there is supposed to be an orifice in one of the coolant hoses under the coolant bottle, but most 8’s are missing them from the factory, do a search, it’s been documented, the purpose of it is to prevent excessive coolant being pumped into heater core to prevent the MIAC noise and improve your cooling.

part number: The part is F100-61-E09 Orifice, Heater Hose

one of the thread https://www.rx8club.com/rx-8-discussion-3/please-help-potential-new-owner-question-miac-181950/page2/

Google search: heater core orifice rx8club