04mbc230

I notice a weird noise today. Perhaps this was here all along, but I guess I didn't notice till now.

Upon start up, more noticeable on cold start, I hear some rattling sound that is coming from the engine area next to the wiper resevoir. I thought there was something loose. I open up my hood to investigate and still hear the noise rattling and very apparent near the wiper resevoir.

The rattle goes away after it warms up a bit or when I gas it while driving. It remains when I stop, when the engine is still cold and goes away when it warms up.

So what is this? Is something loose or broken?

Here's a picture of the location where I hear the noise and pin point it to.



This noise sounds llike diesel engine car kinda rattle. What could this be?

Glyn M Ruck

There are a few things it could possibly be. The power steering pump or pulley which is right where you indicate or a noisy timing chain - however the chain should only rattle until the oil pressure comes up from a cold start. Then the tensioners should shut it up. If it's the chain then you need a new chain & tensioners. The camshaft sprocket drive pulleys can also rattle & need replacement.

Good luck

04mbc230

Here is a video and sound of the noise. It's much more apparent with my hearing than this recording. Perhaps the recorder records everything and my hearing is selective. hhaha

I am talking about the rattling sound. It seems you can hear it more towards that metal plate in the video. The high enginee noise goes away if I close the hood, but that rattle stays.

http://www.youtube.com/watch?v=S-Z4cfEF4bI

Can here it from the driver's wheel well too.

http://www.youtube.com/watch?v=g_XAJ7itUCg

I read that it could be the SC tensioner or the purge valve?

Glyn M Ruck

That's quite a hard metallic knock - It's not what purge valves sound like to me but recordings can be confusing. It certainly does not sound like the 6 cylinder model purge valves. Maybe another M271 owner can chime in. If it's the poly V belt tensioner/pulley it's screwed. They start by making a gritty, dry bearing, shreeking noise.

All this said - I don't like the sound of that at all - it spells trouble. If it's the purge valve you are OK & no harm can be done but most other things could lead to a mess that make noises like that. It could even be the vacuum pump.

Unless someone else has a better idea you should have that properly diagnosed soon. It's certainly not something like a small end bearing or it would become noisier as the vehicle warms up. It could still be timing chain related.

If you want to go on DIYing then get a 6 buck car stethoscope or use a long screwdriver against your ear to track down exactly where the noise is coming from & post. Be careful not to get anything into the moving parts.

pcy

If I were you, I 'd use a mechanic's stethascope and try to pin point the root cause of the noise. If you know what you are doing, you could actually use a long screwdriver and put one end on the suspect componet that is making noise, then wrap other end of the screw driver with your palm and put your ear near the end of the screwdriver. BE VERY CAREFUL when pointing the screwdriver or the stethascope around moving objects like the fan, belt, and pullies.

You may be able to isolate the noise by putting your hand on various components (ABS pump/unit, Air pump, Power Steering Pump, engine valve cover, etc).

04mbc230

If it was the SC tensioner, could this affect the SC from performing correctly? I somehow notice that the SC doesn't kick in as it did normally. I floor the pedal on a incline and there is nothing. Oh, I am driving in C mode. I changed it to S mode and still don't notice the SC. I do notice it goes into lower gears with higher RMP though, hence the sport mode.

LILBENZ230

The SC is always spinning and doesn't have a clutch - so it can't kick in and out on these cars. That is what I believe Glyn has stated before. I would think that if the SC wasn't boosting you would really notice the difference and you would also be getting a CEL of some kind. The only way I ever notice my SC is if the engine is spinning at high RPMs with load, I can hear the whine (wish it was louder, though)

LILBENZ230

Here is a cold start of my car for you to compare.

http://www.youtube.com/watch?v=N4Ocq883vuY

The sudden air sound is what I assume to be the Secondary Air Injection system. It's way amplified on this video (not sure why?) and hardly noticeable in person.

Glyn M Ruck

Only if it seized & threw the Poly V belt. Only AMG cars have a clutched blower. The Eaton on an M271 runs all the time & dumps any overboost. I don't know how to ask this diplomatically so I'm going to just ask.

Have you been revving the crap out of that engine?

LILBENZ230

I rev the crap out of my engine. What are you getting at, Glyn?

Also can you confirm in my video if the air sound that happens when I move the camera to the wheel well is the secondary air injection or the blower dumping pressure?

W203E35

I heard if you remove some kind of shields you can make the SC whining louder but I can't recall which one. The E55 guys were doing it.


That garage brings a lot of memories Matt

04mbc230

Wow... that was scary on that air sound. I thought you had puncher your tire or something. Hmmz.. I don't have that sound at all. Funny thing is, I hear that rattle sound as well on your car. It isn't as loud as mine though.

04mbc230

No.. I drive it in C mode and haven't even put in S mode at all. I am the second owner though. The last time I drove it hard was when I test drive it prior to purchase. I treat this car like a lady and hence she's giving me the whinning as you can hear. HAHA

04mbc230

Well, I guess it's time to bring her in for a check to get this fix once and for all.

LILBENZ230

You should have that air sound. The car's air injection system works when the engine is cold to help warm up the catalytic converter and reduce emissions. The car sounds NOTHING like that in person. I'm not sure why it is so amplified on that video.

Also you are better off driving it hard sometimes than babying it all the time. My car is rode hard and put up wet - but well cared for.

Glyn M Ruck

Yes - I think so & you have answered my question. I hope it's something simple but it sounds as though something is broken. I had to ask the abuse question because in my experience with M271's in SA when noises like that appear the guys have usually chipped the car & disconnected the rev limiter.

04mbc230

Okay. I had a MB Tech looked at it and he heard the noise. He said it is the SC Tensioner needs replacing and he also pointed out that it was time to change the belts too.

I am going to bring it in for service and along with the Thurst Arm bushing be replaced.

I am wondering if this will resolve the shaking while between 60mph to 70 mph. Tire related or this Thurst Arm Bushing related?

Glyn M Ruck

Great if it's just the belt tensioner. It must be really shot if it rattles.

The castor bushes themselves can't cause shake but can amplify it. Balance your front wheels properly.

LILBENZ230

What are you paying for the belts/tensioner change?

04mbc230

Okay. Here's an update. I finally got my car in to a MB Tech and they had taken the parts out to investigate. The tested the SC tensioner or other tensioner and didn't find any issues. The next thing they tested was the water pump. When tested, they found the noise. So now, it is confirmed to be the water pump that is starting to fail and making this noise.

I had them to change out the drive belts as well, since it does looks worn out.

Glyn M Ruck

Ah! Good News! Damn water pump.

04mbc230

Glyn,

Would you know if the water pump is in that area by any chance? I mean on the pictures I posted with where I hear this noise is at.

Thanks.

Glyn M Ruck

The water pump is not exactly where your arrow shows. It's slap bang in the middle if the timing chain case. The way that aluminium chain cases transmit noise it could easily sound as though it is coming from where you indicate. A damaged pump could make the noise you posted. Some have plastic impellers & some metal. I've seen the impeller come right off the shaft on M111 & M271 engines & still not leak through the ceramic seal.

04mbc230

Hmmz.. I guess I just have to find out when I get back the car to see if this noise is still there or not.

04mbc230

Okay. I got my car back. The noise is diffenently gone. Or it may seem. I looked at the old water pump that is taken out and that is one of the most beautiful water pump I seen. Looks like a piece of art! I seen water pumps from acuras, honda, toyotas and this is nothing near this. I guess the price difference for these two cars really show what is top end vs what is low end. Alright, enough admiring the water pump. I guess the water pump was due for a change.

I also changed out the drive belts. The car feels tigher now and not as slugglish, or probably it's because it's been a week since I drove her.

Okay, here's the problem. I still here the knocking!! It's not as apparently anymore. I can only hear it when it's in gear. This is what I did and how i notice it. I was manuevering the car back to it's park spot. While I have to turn the steering while in gear, I hear the knocking!!! The darn diesel noise I had before came back.

It seems that this noise occurs in low rpms, probably around under 1000 rpms to get that noise. I had the tech look at it and now it's back to the possible SC tensioner. Arghhh.. i thought this was the issue from the beginning, but he said he was going to change that out but didn't hear any noise when he got to it. He then investiage other parts and hear the water pump had some noise when he spinned it.

I guess the water pump was an issue but wasn't the actual noise that I pinpointed here. So now.. I am wondering if they would need to take out the drive belt again to get to this part.

Do you think I can live with this noise or does it have to be fix soon?