1990 Mercedes Benz 190e Alarming noise post fan clutch repl

ILVMYBENZ

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1990 MERCEDES BENZ 190E

Noises problem
1990 Mercedes Benz 190e 6 cyl Two Wheel Drive Automatic

My 190 E was overheating. The mechanic found that the fan was freewheeling at higher temps and replaced the clutch.

When I picked up the car it ran at the correct temp and all seemed well.

After several miles, I pulled over to make a phone call and was alarmed by a loud noise from under the hood that I could also feel as a vibration through the steering wheel.

I turned the engine off and observed the following:
(1)The sound would "grind" slowly to a stop even after the engine was off.
(2)The sound would appear at a lower volume and pitch as I turned the key on but WITHOUT turning the engine over. Note that even without turning the engine over, this sound would again slowly "grind" to a stop within several seconds.

I looked under the hood for anything obvious (i.E. Fan shroud interfering w the fan) while the car was off.

Not seeing anything obvious, I started the car again and waited. Within two minutes (engine temp was over 80 degrees C.) The sound returned. I jumped out of the driver's seat and ran to the front to look under the hood. Of course, the noise stopped before I could take a peak under the hood!

Due to the nature of the sound (loud enough to draw looks from folks walking by) and because in over 30 years of driving I have never heard such a sound (except for the time my poly V belt broke after 130K miles!), I made the decision to take the car back to the mechanic.

The car refused to duplicate these noises for the mechanic while we both stood around waiting.

I left the car with him, assuring him that he need not be standing next to the car to hear this sound if and when it returns.

Okay, with this history, I'm hopeful that someone might have an idea of what could be causing this. Specifically, is there anything in the replacement of the fan clutch that may be "off"?

I realize that troubleshooting sounds without the ability to actually hear the sound is difficult at best. That said, my hope is that one of you may have enough experience with the fan clutch replacement to know if anything may have gone astray there.

FYI, the other work I had done was: (a)Valve cover gasket replacement (b)Transmission service: Replace Filter & pan gasket/ drain torque converter

Any thoughts will be greatly appreciated. Thanks in advance.

IlvMyBenz

7 Replies

CARADIODOC

MECHANIC
33,737 POSTS

Look for a second electric radiator fan. When the bearings go out, it will act like you described. I had one that would never make noise in the shop where it was warm. After driving in cold winter air for exactly 8 miles, the howl would start up when going faster than 45 mph. The air flow was spinning the blade.

Once I figured it out, after five or six long test drives, I tied it up to prevent it from spinning. Noise never came back after that. New fan motor solved the problem.

Caradiodoc

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Tuesday, March 16th, 2010 AT 4:00 PM

ILVMYBENZ

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Dear "caradiodoc",

My MB 190 E does have a set of twin AC/Aux fans. These were behaving as they should; no unusual sounds or behavior there.

The air temp on the day in question was 68 degrees.

The noise began with the car at idle and the engine temp between 85 and 95 degrees C.

When I shut the engine off, the noise would grind to a stop.

Upon immediately turning the key to the pre-ignition position, the lower pitched, "growling/grinding" sound (described post engine shut off above) could be heard for several seconds before the sound would stop.

After several attempts, I was able to start the engine without the sound returning. It was at this point that I drove the car back to the mechanic who was thankfully just a short distance away.

Unfortunately, as mentioned, the car refused to duplicate this behavior with the mechanic watching.

The car is at his shop as I write.

This car is like a child (well sort of)- As a mother of 3 human kids, I've been wrestling with the idea of passing this car to my daughter who is in her 2nd year of collage.

Thanks for the input. Any other thoughts?

IlvMyBenz

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Tuesday, March 16th, 2010 AT 5:44 PM

CARADIODOC

MECHANIC
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I would be inclined to blame the new fan clutch, except for your comment about it making the noise before the engine was started. Electric fans will turn on sometimes for a few seconds when the ignition switch is turned on. That would be the giveaway it's one of the electric fans making the noise. Since the noise started right after the fan clutch was replaced, look closer at it.

On some engines, it can be unbolted without affecting anything else, and run that way. If the noise still occurs, at least you know that's not it.

Caradiodoc

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Tuesday, March 16th, 2010 AT 6:03 PM

ILVMYBENZ

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Dear "caradiodoc"

Yea, my inclination is/was to blame the fan clutch installation (obviously). The AC/AUX fans are electric and as mentioned, seem to be just fine. I am fairly sure there is not an electric control for this main fan (thus the temp controlled coil/spring that engages the clutch.)

The fan clutch is just one of many things that the PolyV belt wraps around in this car. I don't know enough about the fan clutch to know if there is any possible way to bypass it for a test. My guess would be no.

I know just enough about a fan clutch to know it's a fairly simply gadget. In the case of this Benz, it was the silicon/grease that had leaked out (I think) that caused the fan to "freewheel" at operating temp with the engine running.

I guess another way to look at what I'm asking is: Is there an incorrect way to install the clutch, ( and/or have a faulty replacement clutch) that could perhaps cause it to not fully engage; or, possibly cause a delay in fully engaging the fan (anything that could result in such a terrible and intermittent noise?)

One thing I didn't think to check was for play in the fan. It did spin freely with the engine off.

Hmmm.I guess I know just enough to frustrate myself!

Of course, as with all things mechanical, there is always the chance that something totally unrelated to any of the work done went or is going on the fritz (that's the option my brain wants to avoid!)

LvMyBenz

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Tuesday, March 16th, 2010 AT 7:12 PM

CARADIODOC

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I am not proposing you do this, but a test I used to show my students was to have a helper start the engine while I was holding onto the fan. You must check first that it is not locked up. As the engine warmed up, you would feel the fan tug harder and harder as the clutch tried to engage. That was proof the clutch was working. The biggest danger came from casually letting go of the blade because it would knock your fingers around as it started to spin. You must let go quickly. Some people do this with a light rope instead of their fingers. You have to be careful how you hold the rope so it will slip through your fingers instead of pull them into the fan if it locks up tightly and starts to spin. Don't use heavy wire because it could tear up other stuff if it starts getting whipped around.

There should be a way to remove the fan and clutch and still run the engine. Some clutch assemblies are held on with a real big nut. When it is unscrewed, you have to look at the pulley. Most are held on with four bolts. If the pulley is loose and falls off-center, then the clutch assembly is required to run the engine.

Some clutch assemblies have a round flange that four bolts go through to hold it on. Those can be removed, and the bolts put back in to hold the pulley tight. You have to watch the bolt length though. That fange is about 1/4" thick. With it removed, the bolts could be long enough to hit something behind the pulley. Simply spinning it by hand before installing the belt will show if it will spin freely.

Caradiodoc