Whine or Whirring from Engine
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Joined: Nov 2024
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Whine or Whirring from Engine
This is a low mileage 2004 E500 (79K miles). When I inspected it prior to purchase I noticed the whine noise and figured it was one of the pulleys. After I bought it and got it home, I pulled the serpentine belt and noticed the idler pulley was broken, so I ordered a new one, installed it and hoped the problem was no longer there.
Still there. So I removed the belt again and rotated all the pulleys. All quiet. I then left the belt off and started the car. The whine is still there. I've read that some people experience problems with the front pump in the transmission, but I don't think that is the problem. Prior to removing the belt, I took a stethescope and put it to the power steering pump and it was clearly noisy, but with the belt removed, the pump is no longer in the circuit and I still have the whine.
It should be noted that it only occurs at idle and low speed. As you get up to speed in the car, you no longer hear it. I'm sure these cars didn't have this noise when they're new, so I'm at a loss as to what could be causing it. Anyone got any ideas before I take it to an independent?
Thanks...
Still there. So I removed the belt again and rotated all the pulleys. All quiet. I then left the belt off and started the car. The whine is still there. I've read that some people experience problems with the front pump in the transmission, but I don't think that is the problem. Prior to removing the belt, I took a stethescope and put it to the power steering pump and it was clearly noisy, but with the belt removed, the pump is no longer in the circuit and I still have the whine.
It should be noted that it only occurs at idle and low speed. As you get up to speed in the car, you no longer hear it. I'm sure these cars didn't have this noise when they're new, so I'm at a loss as to what could be causing it. Anyone got any ideas before I take it to an independent?
Thanks...
Junior Member
Joined: Nov 2024
Posts: 24
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Why wouldn't a video clip containing the noise help? Noises can be hard to describe and cars make lots of noises for lots of reasons. Maybe someone here had a similar noise and could help you troubleshoot. Or they could tell you it's fine and nothing to worry about?
Anyways, if you are taking a 20+ year old Mercedes to the shop just to troubleshoot a noise with no codes or drive-ability symptoms then I'm afraid you have bought the wrong vehicle. Your mechanic is going to love you.
Anyways, if you are taking a 20+ year old Mercedes to the shop just to troubleshoot a noise with no codes or drive-ability symptoms then I'm afraid you have bought the wrong vehicle. Your mechanic is going to love you.
Super Member
Joined: Aug 2004
Posts: 545
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From: Southern California
Are you familiar with Secondary Air Injection System? It could be that air pump that is making the noise. You can test this by unplugging the electrical connection to the pump and starting the car. If the noise is gone, that could be your answer. All of it is right up front just under the smaller engine cover. I am assuming you have M113 engine. Pump is easy to replace. Pelican Parts W211 Secondary Air has a good article. The dreaded P0410 code was mostly attributed to faults in the Secondary Air Injection system.
Secondary Air Injection System was common on cars of that period. Usually it pumps air to the catalytic converters to 'reduce' emissions when the engine is cold. But it also does a check under certain conditions when in drive and you've stopped somewhere. You can hear the air pump kick on. Another way to verify SAIS is to hook up an OBD2 reader and look at the O2 sensor live data. You will see the numbers change when the air pump kicks on.
Secondary Air Injection System was common on cars of that period. Usually it pumps air to the catalytic converters to 'reduce' emissions when the engine is cold. But it also does a check under certain conditions when in drive and you've stopped somewhere. You can hear the air pump kick on. Another way to verify SAIS is to hook up an OBD2 reader and look at the O2 sensor live data. You will see the numbers change when the air pump kicks on.
Last edited by F1Fan; Dec 2, 2024 at 07:33 PM.
Thread Starter
Newbie
Joined: Nov 2024
Posts: 8
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Are you familiar with Secondary Air Injection System? It could be that air pump that is making the noise. You can test this by unplugging the electrical connection to the pump and starting the car. If the noise is gone, that could be your answer. All of it is right up front just under the smaller engine cover. I am assuming you have M113 engine. Pump is easy to replace. Pelican Parts W211 Secondary Air has a good article. The dreaded P0410 code was mostly attributed to faults in the Secondary Air Injection system.
Secondary Air Injection System was common on cars of that period. Usually it pumps air to the catalytic converters to 'reduce' emissions when the engine is cold. But it also does a check under certain conditions when in drive and you've stopped somewhere. You can hear the air pump kick on. Another way to verify SAIS is to hook up an OBD2 reader and look at the O2 sensor live data. You will see the numbers change when the air pump kicks on.
Secondary Air Injection System was common on cars of that period. Usually it pumps air to the catalytic converters to 'reduce' emissions when the engine is cold. But it also does a check under certain conditions when in drive and you've stopped somewhere. You can hear the air pump kick on. Another way to verify SAIS is to hook up an OBD2 reader and look at the O2 sensor live data. You will see the numbers change when the air pump kicks on.
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Well, I know exactly where the whine is coming from! It's the oil pump. Initially I thought it was the power steering reservoir, so I changed that out and it still did it. I have a lift in my garage, so I raised it up and removed the belly pans and used a screwdriver as a stethescope to listen to various pieces of the engine. The AC compressor was quiet, but when I put the screwdriver to the driver side bottom of the oil pan I could hear the whirring/whine. It was distinct and changed in tone and volume as you increased RPM. I then read of some of the forums that this noise is an issue with the AMG models. While mine is not an AMG model is sound exactly like others that have complained of this same issue. Some say to live with the noise. I don't know if I can do that.
I looked at the lower oil pan and there is not a whole lot of clearance between it and the sub frame to remove it and then if I remove it I don't know if the oil pump can be removed without removing the engine. Anyone been down this road before?
I looked at the lower oil pan and there is not a whole lot of clearance between it and the sub frame to remove it and then if I remove it I don't know if the oil pump can be removed without removing the engine. Anyone been down this road before?
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Joined: Feb 2014
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From: MA
2008 E350 4Matic, 2011 E350 4matic
If you don't find anything searching the old threads on here and on benzworld, check the WIS. It's the full dealer repair manual. Stopped in 2020 but would still be fine for your car. Comes with the parts lookup catalog too which is EPC. You can get a knock off copy on eBay in the $20 range.
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