Fuel Pump Noise?
Thread Starter
Member
Joined: Oct 2024
Posts: 225
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From: Pennsylvania, US
2008 C300 4Matic
Fuel Pump Noise?
I have a very weird one for you guys. I have a 2008 C309 4Matic. There has always been a slight whine/screech from the rear drivers side (either the speaker behind the headrest or the fuel pump if the tanks on that side), but it’s barely noticeable and nobody besides me ever has.
Today on my way to work, the reserve fuel level warning came on and at that exact same instant, there was a TERRIBLE screeching sound that was beyond loud from the same place. It did waver based on if I was accelerating or decelerating but only a little. It didn’t stop until I shut the car off and it stopped about 5 seconds after that. I’m leaning towards a speaker because to my knowledge the fuel pump would never make a noise like this, but the fact it came on at the exact same second as the warning is kinda strange. Let me know though, thank you all!
If you do think it’s the speaker as well, could anyone happen to know the part number for that speaker and I’ll just swap it out?
Today on my way to work, the reserve fuel level warning came on and at that exact same instant, there was a TERRIBLE screeching sound that was beyond loud from the same place. It did waver based on if I was accelerating or decelerating but only a little. It didn’t stop until I shut the car off and it stopped about 5 seconds after that. I’m leaning towards a speaker because to my knowledge the fuel pump would never make a noise like this, but the fact it came on at the exact same second as the warning is kinda strange. Let me know though, thank you all!
If you do think it’s the speaker as well, could anyone happen to know the part number for that speaker and I’ll just swap it out?
Super Member
Joined: May 2024
Posts: 508
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From: Northern Indiana
2014 c300 w204.080 3.5 v6
You should get a scanner and there is a speaker test in there that you can fire each speaker separately to see how they sound.
You can also turn the fuel pump on and off with a good scanner and listen for noise.
another thing you can do is look for water getting into the car or trunk in any way. If there's a leak it can cause crazy issues.
You can also turn the fuel pump on and off with a good scanner and listen for noise.
another thing you can do is look for water getting into the car or trunk in any way. If there's a leak it can cause crazy issues.
Thread Starter
Member
Joined: Oct 2024
Posts: 225
Likes: 29
From: Pennsylvania, US
2008 C300 4Matic
You should get a scanner and there is a speaker test in there that you can fire each speaker separately to see how they sound.
You can also turn the fuel pump on and off with a good scanner and listen for noise.
another thing you can do is look for water getting into the car or trunk in any way. If there's a leak it can cause crazy issues.
You can also turn the fuel pump on and off with a good scanner and listen for noise.
another thing you can do is look for water getting into the car or trunk in any way. If there's a leak it can cause crazy issues.
I don’t think there’s any water getting in, I keep a lot of things in the trunk that would definitely hold moisture if they got wet and I haven’t noticed any issues. I have a moisture check tool that inspectors use for checking moisture in walls and ceilings however and I could always use that in the trunk to make sure.
Super Member
Joined: May 2024
Posts: 508
Likes: 124
From: Northern Indiana
2014 c300 w204.080 3.5 v6
I don’t think there’s any water getting in, I keep a lot of things in the trunk that would definitely hold moisture if they got wet and I haven’t noticed any issues. I have a moisture check tool that inspectors use for checking moisture in walls and ceilings however and I could always use that in the trunk to make sure.
Thread Starter
Member
Joined: Oct 2024
Posts: 225
Likes: 29
From: Pennsylvania, US
2008 C300 4Matic
Update: It’s 100% the speaker. I went back to my car to leave and as soon as I unlocked it I heard it start screeching again so I was able to confirm it’s the speaker. It stopped after a few minutes and is ok now, but I’m going to go ahead and take a look at the connector sometime soon and if it looks alright I’ll get a new speaker ordered.
Thank you!
Thank you!
Super Member
Joined: May 2024
Posts: 508
Likes: 124
From: Northern Indiana
2014 c300 w204.080 3.5 v6
Update: It’s 100% the speaker. I went back to my car to leave and as soon as I unlocked it I heard it start screeching again so I was able to confirm it’s the speaker. It stopped after a few minutes and is ok now, but I’m going to go ahead and take a look at the connector sometime soon and if it looks alright I’ll get a new speaker ordered.
Thank you!
Thank you!
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Thread Starter
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Joined: Oct 2024
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From: Pennsylvania, US
2008 C300 4Matic
I believe it’s a sub, but not 100% sure. I do have the Harmon Kardon like @RobertR728 mentioned if that helps. I looked around on the WIS and accessing it actually involves removing the rear seats and removing the C pillars. I honestly will probably just give the amp connectors a cleaning in the trunk and call it a day. If it ever happens again then I’ll investigate more.
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I believe it’s a sub, but not 100% sure. I do have the Harmon Kardon like @RobertR728 mentioned if that helps. I looked around on the WIS and accessing it actually involves removing the rear seats and removing the C pillars. I honestly will probably just give the amp connectors a cleaning in the trunk and call it a day. If it ever happens again then I’ll investigate more.
Super Member
Joined: May 2024
Posts: 508
Likes: 124
From: Northern Indiana
2014 c300 w204.080 3.5 v6
If you find that one of the rear surround speakers or sub are bad then removing the seats and pillars to get to the rear deck cover where the speakers are under isn't really that hard. So dont be intimated.
Last edited by RobertR728; Mar 24, 2025 at 05:13 PM.
