On my 1985 300d: On cold mornings, below 14 F, I have a speed-dependent and cold-temperature-dependent howl that peaks into a kind of screeching (like a belt screech x5) once you get up to 45 mph and above. Cannot be replicated when the car is stationary.

When it begins it could be bad-bearing sound, but as it increases with speed it changes pitch, higher as you go faster. It is hard to pinpoint, sounds like it's coming from the right side, front or middle of the car. If there is a big temperature spike (in particular, wet/slushy roads followed by an overnight snap deep freeze, which has occurred a few times this winter), then is it really bad the next morning.

It goes away after a mile or so of driving, and/or as the engine warms up (is much less prevalent if the car is left to warm up in the driveway on a cold morning).

I have been to see my shop twice, both times of course by the time I get there it's warmed up so no noise. We have been under the car with someone running the car, on the hoist, and cannot hear even a trace of anything (other than a dragging rear left caliper).

I suspected the driveshaft center bearing but it seems fine and certainly makes zero noise when turning on the hoist.

Odd thing is, my wrench has customer guy with an older ML complaining of an identical problem.

One thing that did occur to me, after my last visit to the shop, was that if it's an axle, maybe it's dependent on load, so won't show up off the ground?

Ideas?

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I had similar. New belts fixed it.

I cannot imagine what I am hearing to be a belt.

I could imagine it being a pulley bearing, but that would still leave a question of why it's dependent on the car's road speed (independent of motor rpms or if the motor is under load).

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Sounds like a speedometer cable with a little water in it that is freezing. A temp fix is to lube it but permanent fix is replacement.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Center carrier bearing could certainly make noise loaded that it doesnt unloaded. I hate all the noises that come out in the cold.

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Good shot, but I've had that cold-day speedo cable screech on a couple of cars and it's not the same as this.

Damn it's hard to convey sounds through words. This is intense, like it's coming from everywhere, and more like metal grinding/scraping on metal.

Okay I did not think of that. But wouldn't the bearing make SOME noise unloaded, in that case? This one seems tight and silent when turned.

Part of the weirdness here is that there is a limited choice of things that could/should be affected by water freezing, on the underside of the car.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

You said it was on a lift? Was it <14 degrees when you checked it on the lift?

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

No but the only way to have it on a lift at <14 would be to flatbed it there, or leave it overnight, as the sound goes away after a mile or so of driving and the shop is about 8 miles away. If it comes to that I will splash out for a tow/taxis and do that, but right now I would prefer to not spend that $100.

Honestly given the intensity and volume of it if a bearing was making that noise on the road, I figured it wouldn't sound normal even when warmed up inside a shop.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

One way to narrow down on things. If you can get under the car, squirt some Kroil, BP Blaster, WD-40 etc... on the center support bearing and see it that helps.

If not, then squirt the U-Joint.

I State had Rock and oiled this road, suddenly I got this ear piercing screech from the front of my PU. got out to check under it and saw nothing out of place. got going and it was back. put on brakes and it went away....HMMM

Finally figured it out, a small rock got between the Rotor and the pads. I backed up, and it must have flipped out because it was gone.

Remember the movie "Big Fat Greek Wedding"? the father of the Bride sprayed Windex on everything, that was his fix.


Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Thanks, Charlie. I will try the windex....

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

you must be saved by the bell !!!!

get a (chassis ears) tool to isolate the area of the vehicle.

listen thru a tube to steer you toward the component (stethescope)

leave it overnite when its going to be freezing.

once your wrench verifies, you can (isolate by cancelling systems) to make it come and go.

get your wrench just as interesed in fixing it as you are by trading cars with him

p/s and alternator should be eliminated first. propshaft inspection to be safe for road testing.

have him do all the neglected maintenance while he's looking and you should have his undivided attention

think about the rpm change you describe when you say theres a change in pitch or rate.

now what component has a rotating mass, is belt driven, comes and goes dependent on temperature.
is under the front, can be started or stopped, hates the cold yet makes the cold. slugs when she drinks....

Spray shield on a brake sounds horrible, can be intermittent. But varies w/ wheel RPM. Just have to bend it a bit.

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CC: NSA

All things are burning, know this and be released.

82 Benz 240 D, Kuan Yin
12 Ford Escape 4wd

You're four times

It's hard to

more likely to

concentrate on

have an accident

two things

when you're on

at the same time.

a cell phone.

www.kiva.org It's not like there's anything wrong with feeling good, is there?

Jack the car up and wiggle all of the rear suspention pieces ,inspect the shock ,then move onto the driveline .You also want to see if their is play in the rear wheels ,if so you have some movement from long lived bearings with very little grease packed in the hub if never serviced.

We pretty much covered that Saturday. The shocks have been replaced since this started (did it a little at the very end of last winter, but nothing near this bad), shocks were done in September.

Done, and the bearings sound fine. But thanks for reminding me I never think about servicing them....

Thanks for the input.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Thanks for the input. Most of what you ask was part of our inspection Saturday. We spent half an hour under the car, listening both while it was being 'driven' and to all components while we turned the rear wheels by hand with the shop very quiet (even the heat turned off). Nothing, not even the sound of a worn bearing.

I have tried varying rpms while the noise occurs, by keeping the car in lower gear or shifting between gears, it makes no difference whatsoever. This is why I have not paid much attention under the hood, so far.

The idea of trading cars with the wrench is a good one.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22