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YOUR RESEARCHAnybody can identify this sound
Leading reported evidence
Check bellows
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Suggestion
Have you manually raised your spoiler and checked the bellows?
Leading evidence: 'Check bellows' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check bellows' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion · Original poster
I will disconnect the fan tomorrow and block it with something so it cannot rotate and then go for
Replace crankcase pressure and or the internal modification
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Suggestion
I'm thinking the changing crankcase pressure and or the internal modification that was done may have a correlation to the haunting sound.
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Suggestion · Original poster
Car was ghost free till last week so no relation with the changes there which are there already for two months.
Test indy an internal modification of the cranckcase
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Suggestion · Original poster
I have the AOS back connected to the throttle body as I am testing for my Indy an internal modification of the cranckcase to prevent the AOS sucking up excessive oil from the sump when the diaphragm fails.
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Driving at highway speed from 60mph onwards starts a noise coming from the back. It�s a kind of background poooooow pooooow pooooow
I made a recording and it is still reasonable clear to hear. First pooooow starts at 0:01 second pooow between 0:07 and 0:08
gear/rpm changes have no effect on the sound. Lower speeds I don�t hear it
any idea?
So it starts at over 60mph. So maybe airflow? Have you manually raised your spoiler and checked the bellows? Maybe manually raise your spoiler and see if it still does that. Tires okay and new?
If you�re talking about the higher pitched sound, my guess is it�s the secondary air pump cycling down. Have no idea why it would be doin that, but a few times as Ive gone to park it will come on and when I shut the engine off with it running it makes a similar sound. Just a thought.
Silk - Is there a vent for your catch can system? Sound cycles from high to low pitch. I can�t figure what else is resonating or venting. It doesn�t appear to be a machine noise though.
At the moment I am not running the AOS modification routing the AOS line to the airbox. I have the AOS back connected to the throttle body as I am testing for my Indy an internal modification of the cranckcase to prevent the AOS sucking up excessive oil from the sump when the diaphragm fails. It should safeguard your engine from a possible hydrolock when the AOS fails suddenly and hard. Initial test with a broken AOS have proven it works. And also on my car the AOS failed and no excessive symptoms were present. Eventually I will go back to the routing to the air box (with it Without catch can) as it is also a safeguard for preventing oil going into the intake via the AOS coming from the heads.
Car was ghost free till last week so no relation with the changes there which are there already for two months.
could it be a wheel bearing?
Listened to it three times with head phones on, couldn't hear a thing. My thoughts, forget it for now, when it starts getting worse (if), then it will be easier to troubleshoot.
The AOS that's in now is good or one that has failed for testing?
Do you have a remote mic you can set up and move it around in the engine bay to try an pin point it's location?
Same here. I'm thinking the changing crankcase pressure and or the internal modification that was done may have a correlation to the haunting sound. Just a wild guess...Or the cooling fan cycling on and off?
Silk, has your INDY heard this yet?
The internal modification has no effect on internal cranckcase pressure.
I don�t think it has anything to do with it. The sound is not rpm dependent. It comes at a certain speed. Going faster it becomes more constant. If I drive on the highway and shift to neutral, rpm falls to idle, it does not change th� noise pattern, it only slowly disappears when slowing down under a certain threshold speed.
I have a suspect. Need to do a test tomorrow. Now it�s dark already. It sounds really ridiculous. But I think it has to be it. Almost a ghost!!!
Couple of months ago I noticed the engine bay fan in the spoiler started squealing when it turns on. I suspect with spoiler up, the fan rotor catches the moving air and starts whirring till it reaches a certain speed and it starts to the squeal (vibrations). Internal
friction (the squeal) slows down the induced fan rpm and noise disappears, fan speeds up and noise comes back. The faster I drive the noise stays.
I will disconnect the fan tomorrow and block it with something so it cannot rotate and then go for
a drive and check if the noise is gone.
I don’t think it has anything to do with it. The sound is not rpm dependent. It comes at a certain speed. Going faster it becomes more constant. If I drive on the highway and shift to neutral, rpm falls to idle, it does not change th� noise pattern, it only slowly disappears when slowing down under a certain threshold speed.
That smells like the transmission or trans axle, or clutch, throw out bearing...
It is something with the fan. Directly or indirectly. Today driving to work I made a bit of a detour and did some tests:
1. Unplugged fan connector / blocked the fan blades: no poooow
2. Unplugged connector / unblocked fan: no poooow
3. Plugged connector / unblocked fan: yes poooow, most audible when spoiler up
I suspect the engine compartment sensor is bad or it got loose and is hanging somewhere where it gets hot and the fan switches on and starts squealing and vibrating in the driving wind with spoiler up.
Did not got further tracking down as I am not with the car to verify right now.
I was thinking fans too. There are also 2 fans in the front if you can�t figure out the rear fan to be the cause. A fan would slow down from a faster speed if the bearing is problematic, which is often why a fan could fan.
