loud engine noise
Thread Starter
Senior Member
Joined: Jul 2007
Posts: 421
Likes: 14
From: Bay Area
2004 E500 CLK320
loud engine noise
First of all, sorry for posting this thread in this forum. I’m running out of ideas in trying to identify the cause of this problem. The members in this forum are fairly active and enthusiastic about their MBs, I’m hoping that I may get some help here from you guys. This is actually a 2004 CLK320 w/ 80k mi. Since the CLK320 shares the same engine as the E320, I’m hoping someone here may have seen/experienced this problem in their E320. Just recently, a loud low-frequency grinding noise has been coming from the front left (passenger side) of the engine compartment at idle. The noise seem to be loudest near the alternator, and it gets louder at higher RPM. However, there’s no loss of power. It’s still as powerful as ever. I removed the drive belt and checked out all the pollies by hand; all the pollies seem to be tight and the bearings are smooth. The noise sounds more like metal hitting against metal. See the video in this link.
http://www.youtube.com/watch?v=N5G-KL6RGGo
http://www.youtube.com/watch?v=N5G-KL6RGGo
MBWorld Fanatic!
Joined: Jun 2007
Posts: 1,936
Likes: 349
From: Huntington NY
S560
A pulley might feel fine while it is manually spun, but that is far different than when under tension and spinning at 1000 rpm. It sounds like a pulley might be the problem. I used to diagnose this by removing the belt and starting the engine to see if the sound is still there. I do not know off the top of my head what is driven by the MB belt (beyond a/c PS, alt etc), but I would imagine there would be no long term harm to try running the motor for 3-5 seconds with the belt off. If the noise is still there then the next culpret could be the cam drives.
MBWorld Fanatic!
Joined: Jun 2007
Posts: 1,936
Likes: 349
From: Huntington NY
S560
You could also try hitting the pulley bearings with some WD40 while running, if the noise lessens or goes away than you know it is the problem (sometimes grinding bearings will show no change since they are far gone)...
MBWorld Fanatic!
Joined: Jun 2007
Posts: 1,936
Likes: 349
From: Huntington NY
S560
I woud just pull the belt for a few seconds and see if the noise is gone before pulling pulleys. If it does go away then start spraying pulleys to find the culprit (if you cannot audibly tell)...
Thread Starter
Senior Member
Joined: Jul 2007
Posts: 421
Likes: 14
From: Bay Area
2004 E500 CLK320
With the belt removed and nothing is connected to the water pump pulley, does the alternator need to be driven as well in order to keep the car running for a few seconds and not resulting any damage to any electronics or mechanical parts in the engine? I have tried this on cars with two belts, i.e. with the AC compressor disconnected, but never on cars with just one belt.
Senior Member
Joined: Apr 2007
Posts: 311
Likes: 73
From: Richmond, Virginia USA
'12 E550, '10 ML350, '06 E350, '20 GLC300, '21 GLC300
Try using a wooden dowel rod or stick around 24 inches long. You will use the rod like a stethoscope. Very carefully, touch the center of each pulley with one end and your ear on the other end. BE VERY CAREFUL around rotating equipment. Don't have any dangling clothes or jewelry on either. Sounds will vibrate the wooden rod. You'll know when you get close. Do this without taking any belts off. Good luck.
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Thread Starter
Senior Member
Joined: Jul 2007
Posts: 421
Likes: 14
From: Bay Area
2004 E500 CLK320
Using a stethoscope sounds like a great idea. However, I won't use a wooden rod thought -- sounds kind of dangerous, I don't want to have my ear cut off while listening for noise. Ebay sells stethoscope for cars for around $10. I think I'll try to start the car with the belt off, the battery should be able to keep the car running for a short while.
http://cgi.ebay.com/ebaymotors/MECHA...motiveQ5fTools
http://cgi.ebay.com/ebaymotors/MECHA...motiveQ5fTools
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Member
Joined: Jan 2007
Posts: 75
Likes: 0
From: NW Chiburb
04 E500
It may be the belt itself. It's a hard to be sure because the camera is moving around, but it appears from the video that the sound comes and goes in sync with the white flash on the belt. If the noise was from a bearing, I'd expect it to be more constant.
I'd take another look, and if that is really the case I'd try a new belt. If that cures it I'd double check the pulley alignment, and maybe the belt tensioner.
I'd take another look, and if that is really the case I'd try a new belt. If that cures it I'd double check the pulley alignment, and maybe the belt tensioner.
Thread Starter
Senior Member
Joined: Jul 2007
Posts: 421
Likes: 14
From: Bay Area
2004 E500 CLK320
After doing some more search online and in youtube, the noise seems to be from a failing alternator, where the bearing is making noise when under tension or load. This kind of grinding noise is well documented and has a distinctive sound from pullies and belts, and you'll find all kinds of articles about this problem when you do a search online. I'm going to use a section of the garden hose as a stetheoscope to confirm that the noise is from the alternator before buying a new/rebuilt alternator. Other videos posted on youtube had the same grinding noise from the alternator.
http://www.youtube.com/watch?v=ZBIktSdXLsU&NR=1
http://www.youtube.com/watch?v=Ya_rlzLZTOI&NR=1
http://www.youtube.com/watch?v=ZBIktSdXLsU&NR=1
http://www.youtube.com/watch?v=Ya_rlzLZTOI&NR=1
Member
Joined: Nov 2007
Posts: 164
Likes: 1
From: Grand Prairie Texas
'24 GLE53 AMG Coupe
My friend Douglas had the exact same grinding noise (on his CLK) and it was the alternator shaft bearings.
He got an aftermarket alty and it's performed fine. But he bought a alternator rebuild kit and attempted to rebuild his. He gave up (on it) rather quickly.
He got an aftermarket alty and it's performed fine. But he bought a alternator rebuild kit and attempted to rebuild his. He gave up (on it) rather quickly.
Thread Starter
Senior Member
Joined: Jul 2007
Posts: 421
Likes: 14
From: Bay Area
2004 E500 CLK320
I bought a stetheoscope from ebay for $10. After listening to different parts of the engine, the problem is definitely from the alternator. I highly recommend using the stetheoscope in identifying the locations of the noises. I just ordered an alternator rebuilt online.
Senior Member
Joined: Oct 2006
Posts: 258
Likes: 1
From: socal
sounds like the idler pulley, I just replaced one on my SIL car. it is the upper most pulley. Pull the belts off and turn the pulley by hand if it is bad you should be able to feel it. I think it was less than $50 for the pulley at the dealer my cost.
Last edited by health services; Feb 16, 2010 at 09:41 PM.
Senior Member
Joined: Oct 2006
Posts: 258
Likes: 1
From: socal
it almost sounds like a cage fell apart in your bearing.
MBWorld Fanatic!
Joined: Mar 2006
Posts: 3,254
Likes: 15
From: Louisiana
03 E500 and Corvette
I also bought a pulley from Autozone for about $20. Ok,, not MB part. However I looked at the pulley and bearing installed. Then I put the failed MB part in my lathe, machined it for bearing removal and found the bearing in the MB part was identical in brand and number to the AZ part at $25 less.
My guess is MB outsources the pulley to the same company.
