Viper98912

I don't remember exactly when this started, but I don't remember hearing it before. I've developed an engine whine and wanted to know if anyone else here has heard of something similar. AC was off and so was the radiator fan, and the engine was warm (drove home from work). It is RPM based. Turning on the AC and radiator fan didn't make it go away or get louder. I don't have anyone to rev for me while I looked, but I will tomorrow. I'm also going to compare to another C55 this weekend.

Let me know what you think.
http://s372.photobucket.com/albums/o...t=C55Whine.flv

This is not to be confused with the startup roar which I videotaped here. Notice you can't hear the whine in the background (this video is 6+ months old)
http://s372.photobucket.com/albums/o...=C55Engine.flv

I've also noticed a very loud electronic whine when starting in the mornings as well. I'd say 10x louder and higher pitched than HID ballast whine. But it eventually goes away, or it comes back for a few seconds right as I get home and come to a full stop.

Ideas?

thegreatfnr

I'm not technical enough to give an idea but it def doesn't sound right from the video. Does the noise come and go, does it do it while casually driving?

Viper98912

I think the noise stays constant during all driving, but I can't 100% tell because of wind and road noise.

320 dreamer

sounds like power steering whine to me. check fluid level. possible p/s pump failure

creep305

I had a similar sound in my E350. It was the A/C compressor cluth pulley. Cost me $300. Check that. Hope this helps.

mwc55

Possibly a/c compressor. Belt tensioner is another possibility.

Viper98912

Just checked the PS fluid and it's on the low end, but then again my car has been sitting for about 4 hours. So technically it's ok if it's in the cold reading range. I'll have to recheck it tomorrow after its fully hot. I might check a full lock and see what I hear.

A/C pulley maybe, but it didn't get any changes with the A/C on or off, it sounded exactly the same when revving.

What I really need to do tomorrow is get the gf to rev while I listen up close. I'll let you guys know what I find but please keep the suggestions flowing.

Phil C55

Mine has always had some bit of a slight whine I would say. It's been to the MB garage and the master tech didn't say anything sounded odd to him, but then I didn't ask either. I had one guy looking at the engine (just BSing not looking for anything wrong) and he said "wow, this thing kinda sounds like it has a blower". My car has sounded the same since I have had it and it's never gotten louder so I have kind of figured it's how it's supposed to be.

FrankW

sounds like one of the idler bearings have gone bad.

this is how mine sounded when the supercharger bearing went bad. http://www.youtube.com/watch?v=LAcmJRZrpBo

I also had one of the idler bearing went bad and blew apart. no sound clip tho, but pretty much the same noise. it comes and goes because when you stop and let off the belt tension decrease and engine noise dies down which makes the grind more apparent.

F1Bobby

Mine has a similar sound but goes away after a couple minutes.

Phil C55

A simple way to isolate any sound in an engine compartment is to stick use a section of hose up to your ear and move the other end near the parts. I saw this trick in a factory GM shop manual back in the mid seventies to isolate a lifter tick. It works great, when you get the hose by the part making the noise it will become VERY obvious where it's coming from.

Viper98912

Surprisingly, I think it might be the air pump at the front of the car. At first I thought it was the power steering, but then decided to take off the front engine cover. When doing that, the noise becomes louder and lower pitched. Of course, I'm still not 100% sure, because you *think* thats where you mostly hear the noise from. The car was warm btw, and it sounded different than when its cold (louder and more lawnmowerish).

What's the possibility of the $368 bosch air pump going bad? I thought the air pump was only supposed to be on when the car was fully cold? The car was hot?

MBtech1098

Definitely either your idler pulley, or your AC pulley. The noise will not really change with the AC on because there is no clutch, the compressor is constant drive, it uses a wobble plate to vary compressor output. Both parts mentioned have updated parts due to whine noise...you just got to figure out which one it is. If it is the AC pulley, special tools are required.

W203Ramos

had the same symptom

Had this same sound a few months back and thought it was the air pump...but just for the hell of it I topped off the power steering fluid...I'm talkin 6ml to be exact( used a syringe ) and the sound was gone. give it a shot..might save you some $$$ .....BTW the air pump goes on and off intermitently.

John

Viper98912

*sigh* yes, at the same time I was wondering if it was the idler pulley that was right there, because it really is hard to tell. I guess I'll do more searching tomorrow

Viper98912

At least the idler pulley is only $20 new

F1Bobby

Thanks I'll take a look...

Phil C55

Might want to read my post #11, it simplifies the whole searching process.

Viper98912

lol actually I did take your advice and do this today! First I grabbed a metal pipe which was going to be too long, then I grabbed some thin and long rubber tube, it proved to be too long and thin. Then I grabbed a paper towel roll, but that didn't work either. I'm going to see if I can find something around the house tomorrow and try again.

AMGC43C55

remove your drive belt if the noise goes away you know it's from the front of the engine. but i have heard a noise like this it was the transmission front pump.

advans

I have that whine too, but only after a star, sounds like a SC or Turbo whine. I'm gonna check it out

Phil C55

You want to use something like heater hose or a piece of garden hose. Rubber that has anywhere from 1/2" to 3/4" I.D. works best.

320 dreamer

go to harbor freight and buy a 2 $ mechanics stethoscope!

Viper98912

As I was on my way to go to Northern Tool/Harbor Freight/Sears this morning to get a stethoscope, I decided to rock back and forth all my pulleys by hand. Sure enough, the idler pulley had some slight play. I then remembered my dad taught me a little trick when I was young - put a long screwdriver to the block, and put your ear on the other end (a makeshift stethoscope). Turned on the engine and sure enough, the block the pulley sits on was whirring like a **** at the end of my screwdriver. So this makes me very relieved that it's only a $17 part and I'm 99% sure its the problem.

I read somewhere on here that the torque spec on this T50 bolt is 15ft-lbs. Can anyone confirm this?

I'm also going to buy some Pentosin power steering fluid as well, since when my engine was hot it was still reading at the low mark of the 20C area.

MBtech1098

Screwdriver method is a good method, if you have a long enough screwdriver...tubes work better for whiring or ticking noises, screwdriver works best for bearing noises.

Torque is 25 Nm...about 18.5 ft. lbs.