Engine rattle when AC turns on

[jamestemperante]

Hello everyone! Hope all is doing well,

I have a small concern regarding my 2013 Subaru brz manual transmission

I have a rattling sound coming from the engine bay every time my AC compressor turns on. It's like something is lose, The sound goes away if the ac compressor turns off, or if I press on the clutch pedal, also the sound goes away if I shift the shift knob from left to right (neutral position).

here is a video for your reference.

https://www.youtube.com/shorts/2XHeeVqwcj4

Thank you for your time reading this and I hope you can help me.

Note: I recently replace my throw out bearing and clutch. flywheel is still stock, I think? I bought the car used

[Ohio Enthusiast]

Sounds like normal transmission input shaft chatter due to elevated RPM when the AC compressor is engaged. Do you have any stiffer transmission mount bushings and inserts? These amplify the noise.
Depressing the clutch disconnects the engine from the input shaft, stopping it from spinning and thus not making these noises. Moving the shifter puts some pressure on the forks which might also quiet it down.

[jamestemperante]

I think transmission mount is still stock. The rattle comes when I'm not pressing the clutch pedal, when I press on the clutch, the rattle goes away.

[tomm.brz]

it s still the throw out bearing. Even the newer one is loud i ve changed FOUR of them, all installed by certified subaru techs (not a scammy shitty garage but people who already rebuilt many different brz's) all of them lasted super silent like 15 minutes maybe less
Then all of them started chirping at idle when clutch not engaged
ignore it.

[Ultramaroon]

Originally Posted by Ohio Enthusiast

Sounds like normal transmission input shaft chatter due to elevated RPM when the AC compressor is engaged. Do you have any stiffer transmission mount bushings and inserts? These amplify the noise.
Depressing the clutch disconnects the engine from the input shaft, stopping it from spinning and thus not making these noises. Moving the shifter puts some pressure on the forks which might also quiet it down.

^^^this^^^


I didn't hear any difference until the fan started. All you're capturing there is wind noise. Make a good recording of the difference you hear between clutch engaged/disengaged. ...inside the cabin with windows closed.

[FR-S2GT86]

Or it could be something worse:



This came out of a Dodge Caravan with less than 100K miles on it. It made the same noises as you are describing...AND...still started and ran! Only difference is this had an automatic transmission.

Stranger things have been found.

[jamestemperante]

I'll try to get another video out of it. for the past few days. rattle is a bit less noticable. It usually loud when I use the car during the day when temp are hotter. I live here in the Philippines.

[riboyster]

Did you swap out with a light-weight flywheel? Mine rattles now because of that. I'd reckon its either the flywheel or throw-out bearing. My TOB took a shit at around 50k miles, so if you haven't changed yours yet, it's probably time.

[jamestemperante]

I don't know if my car has an aftermarket flywheel. Bought my car used @ 42k KM.

[ZC6_STi]

Sounds normal to me. It could be the OEM front pipe or over-pipe heatshield that might be rattling whenever the A/C is turned on. I had that happen before when I was all stock.

[jamestemperante]

Hello guys sorry for the late reply.

Here is another video of the rattle, I hope you can hear it, rattle goes away when I press on the clutch.

https://www.youtube.com/shorts/CtrJgbTc6W8

[gpvecchi]

Do you have lightweight flywheel or pulleys?

[jamestemperante]

I'm not sure if I have a light flywheel, I bought the car used. I recently changed my TOB and clutch

[jamestemperante]

attached here is a more clear sound / video of the rattle. Pls excuse my toe nails tho. lol