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We have had a few threads on here about whiny sounding C-Class cars. It often is a belt tensioner or alternator. Symptoms are a drill like sound the goes up in pitch with engine RPM. It usually seems to be the C250 but I've seen mention of other models doing this too.
I had my tensioner replaced but it only helped slightly.
Last night I was watching a youtube video of a C250 and it was making the same drill like sound mine does. Then out of curiosity I checked a few others out. One C250 sounded beautiful. It didn't have that loud, high pitched sound.
I was on a nice drive the other night but totally hating my car as that sound grated my nerves. I'm going to try the dealer year again and see if something can be done, perhaps a replacement of the alternator.
I'd like to know from people here if you do or don't get the sound and what model. I'd be curious if there are any non whiny C250 cars on here.
Most likely it is the alternator and may or may not be tied to a problem. In my experience the whine usually is tied to periods of high output. If it does it after an overnight cold start and then goes away I wouldn't worry about it. If it is persistent, that would suggest the alternator is really working hard and would warrant a thorough check of the charging system.
The only whine I hear in my C250 is the turbo. This is my first car with turbo, at first I wasn't sure if it was normal, but its very quiet overall and I've always been told everything sounds normal when the dealer has had it.
Silent mine is not . It sounds like a power drill winding up. It sort of goes away once the RPMs climb high enough.
I wonder if the cutoff feature that is blamed for the alternator developing this can be disabled ? Given it's only a 2013 I'm not sure how long a new one would last.
The only whine I hear in my C250 is the turbo. This is my first car with turbo, at first I wasn't sure if it was normal, but its very quiet overall and I've always been told everything sounds normal when the dealer has had it.
You may have the same issue then. The turbo is rather quiet in this car. An unmuffled turbo has more of a groan, gravely jet engine kind of sound that comes on under heavy throttle.
If you are applying gentle throttle and you hear this it's probably not the turbo. Also, turbos don't do much in park or neutral.
The GLA with the 2.0 does have a very loud turbo. It startled me the first time I heard it.
The only whine I hear in my C250 is the turbo. This is my first car with turbo, at first I wasn't sure if it was normal, but its very quiet overall and I've always been told everything sounds normal when the dealer has had it.
My C250 1.8 liter coupe whines during initial low speed acceleration. Could be the turbo (but chances are low - I really think it's the transmission).
I've never complained to the selling dealer. The 30k service check was cool (no problems noted - other than brake pad wear).
So it doesn't sound anything like an electric drill?
I have a front tire that's a bit chewed up so between that and the whine my car feels and sounds worse than an old beat up junker, lol. But the C250 video I saw sounded amazing.
I still think many people could be confusing this issue with the turbo. At least with me the sound comes from the front right of the engine and the turbo is in the back bottom right side of the engine. And it wines just as loud without any engine load while in park.
The turbo is very quiet. This is my 4th turbo charged vehicle. Most people work hard at getting them to make some noise.
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No electric drill. My c250 and GLC 300 both sound completely different. My 300 is actually louder due to its injection system. I can here it's turbo. I really cannot really here the turbo on my 250
My 2010 C300 has been making a pretty bad whining noise over about 2k RPM and also a really rough sound while it has been idling for the last few months. After taking off the drive belt and then after verifying with a mechanic's stethoscope I've narrowed it down to the alternator. I assume one or both of the bearings are completely shot.
That said instead of spending > $300 on a remanufactured alternator or almost $1000 for a new unit from the dealer I'm going to try replacing the bearings myself for about $60. Just waiting on the bearings to arrive and for some good weather to do the work.
My 2010 C300 has been making a pretty bad whining noise over about 2k RPM and also a really rough sound while it has been idling for the last few months. After taking off the drive belt and then after verifying with a mechanic's stethoscope I've narrowed it down to the alternator. I assume one or both of the bearings are completely shot.
That said instead of spending > $300 on a remanufactured alternator or almost $1000 for a new unit from the dealer I'm going to try replacing the bearings myself for about $60. Just waiting on the bearings to arrive and for some good weather to do the work.
Thanks, I'm curious to see how that goes. I've never messed with anything on the serpentine belt before but I would do this if it had results. Perhaps you could use better quality bearings or grease?
I'd say it's too hot here already to be working on cars, lol.
Thanks, I'm curious to see how that goes. I've never messed with anything on the serpentine belt before but I would do this if it had results. Perhaps you could use better quality bearings or grease?
I'd say it's too hot here already to be working on cars, lol.
I was able to get a Nachi brand bearing for the small bearing but I was only able to find the larger bearing in an off-brand from a bearing supplier here in Canada. Their spec sheet for the large bearing seems like it's fine and it's intended specifically for alternator applications (probably because this bearing seems like it's only found in Bosch alternators lol) so I'm going to give it a shot. The alternator in the C300 is pretty easy to access so even if one of the new bearings fails in a few years it's not a huge hassle to replace again.
If the dealer can't or won't do anything about it I may give this a try. I've done plenty of repair jobs but have always been nervous about the belt driven components.
They sent my car back yesterday since they spent all day working on trying to get the CD player to work. I have to reschedule for a loaner.
I was able to get a Nachi brand bearing for the small bearing but I was only able to find the larger bearing in an off-brand from a bearing supplier here in Canada. Their spec sheet for the large bearing seems like it's fine and it's intended specifically for alternator applications (probably because this bearing seems like it's only found in Bosch alternators lol) so I'm going to give it a shot. The alternator in the C300 is pretty easy to access so even if one of the new bearings fails in a few years it's not a huge hassle to replace again.
I'm not sure if a C250 is as easy to access. The alternator is bottom left side of the engine. It's down there a bit. I took off the top tray and intake line to get a listen under there and it could be from that area. I can't seem to find any good DIYs on digging into the engine compartment.
Well, I will see sometime after Wednesday what the dealer says.
I haven't gotten the car back yet but they called and gave me a run down of the work done so far. It seems like the alternator was ok but they replaced one of the pulleys. I have my fingers crossed it will be quiet when I get the car back!
On a side note, I'm in a CLA250 now and am surprised how much I hate this car. It looks like a Mercedes but drives like a 2000 era Dodge.
Ok, car back from the dealer but the whine is still there. I picked up a mechanic's stethoscope and had some fun with it. But I located exactly where the sound is coming from. I think it is the AC compressor. But having the AC off doesn't seem to help.
When I touched the probe to the top item on the serpentine belt (center of photo) it sounded like a buzz saw cutting through hardwood. But the pitch was spot on. In hearing more detail it sounded like a pulsating waveform. Like you could hear the individual blades of a circular saw biting into something.
It's a fun tool. The intercooler and turbo parts sound like a purring tiger. Everything sounded nice but that part shown above. The alternator had a hum but nothing obnoxious.
Ok, car back from the dealer but the whine is still there. I picked up a mechanic's stethoscope and had some fun with it. But I located exactly where the sound is coming from. I think it is the AC compressor. But having the AC off doesn't seem to help.
When I touched the probe to the top item on the serpentine belt (center of photo) it sounded like a buzz saw cutting through hardwood. But the pitch was spot on. In hearing more detail it sounded like a pulsating waveform. Like you could hear the individual blades of a circular saw biting into something.
It's a fun tool. The intercooler and turbo parts sound like a purring tiger. Everything sounded nice but that part shown above. The alternator had a hum but nothing obnoxious.
I'm not too familiar with the AC clutch assembly but that could mean that the bearing in the AC pulley itself is the problem which may actually be a cheaper repair (fingers crossed!).
That said I was able to replace the bearings in my alternator! It was a bit of a pain in the butt because of all the corrosion from ~6 years of dealing with road salt but it's all quiet now so I'm pretty happy with the results
Is that the compressor? It doesn't look quite like what I'm finding in the parts photos.
I'm not even sure if the sound is normal or not. I've just never heard a car sound this loud from 1,500-2,200 RPM.
Oh I had assumed you had already positively identified it and I kinda glossed it over... Sorry, my bad. Could it be the power steering pump? I can't see from the photo but if it is the power steering reservoir should be attached to it I think.
I think you are right. That looks closer to the pictures of the power steering pump.
If the power steering fluid is too low it would cause the pump to be noisy as air gets into the lines and causes cavitation in the pump assembly. Eventually this can damage the pump but the fluid level would definitely be the first thing I'd check.
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. It sounds like a power drill winding up. It sort of goes away once the RPMs climb high enough. 
