Is this sound air in cooling system

crazyone64

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May 2, 2018
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I notice a strange brrrrrrrp sound at idle or driving.
It's either coming from the radiator/upper rad hose, or from the k&n filter which I just recharged.
I have no issues with heat, it does not sound like water boiling or rushing through.
I did add some antifreeze last year when it was a little low. It visually looks ok, no oil ontop, no smoke from the exhaust.

I tried purging following "Ford Quick Tips #69: The Trick to Purging Air From Your Cooling System "
View: https://www.youtube.com/watch?v=4gk4xb9aOgE&ab_channel=FordTechMakuloco


Seemed to help a bit but not sure if it was my filter being cleaned or that purge. Also squeezed upper rad hose to push some air bubbles.
Attached is the sound most evident at 1 and 4 second mark. They are short almost vibrating sounds, repeating every now and then.

Please let me know what you think this resembles, I don't know what else to troubleshoot
 

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7991LXnSHO

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Is the sound a lower pitch and occurs twice on the recording?
Some type of mechanic’s stethoscope will help. They are Cheap at HFT, but a hose to your ear or a long screwdriver (handle side towards the ear, please!), can also help chase down noises. Keep them all out of moving parts. We can guess, but if you chase down the location for sure, a probable cause will be easier to get right. Right now, I am debating between a heater door run wild and cooling system indigestion as my top two guesses.
 

crazyone64

Member
May 2, 2018
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Toronto Canada
Is the sound a lower pitch and occurs twice on the recording?
Some type of mechanic’s stethoscope will help. They are Cheap at HFT, but a hose to your ear or a long screwdriver (handle side towards the ear, please!), can also help chase down noises. Keep them all out of moving parts. We can guess, but if you chase down the location for sure, a probable cause will be easier to get right. Right now, I am debating between a heater door run wild and cooling system indigestion as my top two guesses.
Yes, that lower pitch that happens twice in the recording. If it is the cooling system, any next steps? Did you mean heater *core* ?
 

7991LXnSHO

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There’s nothing (at least there is not supposed to be) in the air filter to move and cause a gurgling sound. The cooling system includes anything with antifreeze and water mix going through it. If it is the upper radiator hose, the burping did not get all the air out is my bet.
 

crazyone64

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May 2, 2018
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Toronto Canada
There’s nothing (at least there is not supposed to be) in the air filter to move and cause a gurgling sound. The cooling system includes anything with antifreeze and water mix going through it. If it is the upper radiator hose, the burping did not get all the air out is my bet.
Thank you for helping to troubleshoot, I tried the screwdriver and it really sounds like it's coming from the air intake. Perhaps gurgling isn't the right word, it's more of a vibration brrrr sound. I tried holding the actual filter it doesn't vibrate or dampen the sound by holding it. I don't hear the sound close to the throttle body.

** I notice it is more present when i have the heat on high pointing at the windshield, i can replicate the sound doing this. It is almost consistent.
Once i turn off the Air, the sound is 1 second every few mins. Hoping this clue helps
 

7991LXnSHO

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That sounds more like a flap door and actuator going wild due to a vac leak. I do not have a vac line diagram for your car. On the Fox and many other vehicles, there is a vac canister (and check valve) to power the ventilation system controls. If you have a cracked like or damaged canister, there will not be power to hold the flap in place.
Tag - can someone with a correct diagram pick this up?
 

crazyone64

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May 2, 2018
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Toronto Canada
Hi, I was doing some more tests and observations today and noticed:
When the vent is on, there is no sound, cold or hot.
When the AC is on, the sound is present. cold or hot.
I can hear the AC compressor clicking on every time the sound starts.
Please take a listen to a better sound clip, you'll see what i mean.
 

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crazyone64

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I took out the whole intake assembly, ran the car for half a minute, and confirmed the sound is coming from the throttle body, most present when the ac compressor turns on and it requires that extra air.

Any thoughts what's going on now that's ive isolated it a bit more.
No longer related to coolant, filter, heater core, ac,
 

crazyone64

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7991LXnSHO

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IAC’s are supposed to be silent. If you have an aftermarket TB, some whistle. Myy 5.0 BBK whistles an F# when open. (I leave the internal edges sharp so I can tell it is working. :)
But where it is and when it makes noise makes me suspect the IAC.
Leave it unplugged, start the car and listen while keeping it running. You can hear it in the car, right?
 

crazyone64

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May 2, 2018
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IAC’s are supposed to be silent. If you have an aftermarket TB, some whistle. Myy 5.0 BBK whistles an F# when open. (I leave the internal edges sharp so I can tell it is working. :)
But where it is and when it makes noise makes me suspect the IAC.
Leave it unplugged, start the car and listen while keeping it running. You can hear it in the car, right?
Stock TB.
I unplugged the IAC, started the car, gave it enough gas to stay alive.
I can NOT hear the sound anymore!
I can also now see the RPM jump and decrease 300 or so, as the AC compressor clicks on/off. It stayed constant with the IAC plugged in.

Does this confirm I need a new IAC? Any additional thoughts given the test i performed?
 

7991LXnSHO

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I say it is worth the cost and low level of labor to try a replacement. If the noise is gone while detached, and it functions with and without it correctly, that’s not like a random replacement of parts.
 

crazyone64

Member
May 2, 2018
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Toronto Canada
Stock TB.
I unplugged the IAC, started the car, gave it enough gas to stay alive.
I can NOT hear the sound anymore!
I can also now see the RPM jump and decrease 300 or so, as the AC compressor clicks on/off. It stayed constant with the IAC plugged in.

Does this confirm I need a new IAC? Any additional thoughts given the test i performed?
I'll take if off tonight and post a couple pics, before TB cleaner and after.
I say it is worth the cost and low level of labor to try a replacement. If the noise is gone while detached, and it functions with and without it correctly, that’s not like a random replacement of parts.

Looks a lot better, but sadly the issue remains.
It's present when the IAC is plugged in, and not present when the IAC is unplugged.
 

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crazyone64

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Part arrived today. Identical fit.
After installation....... the sound is 90% gone!
Firstly, thank you so much 7991LXnSHO ! You were correct in diagnosing.
Second, now that we know it was the IAC, anything i should check next, the remaining 10% has me curious why it remained.
 

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