M103 Fan Clutch Issue - PeachParts Mercedes-Benz Forum

Rahulio1989300E · #1 04-30-2011, 04:05 PM

Hello Peaches!

I just replaced my fan clutch for a few reasons:
1. It is hot in Texas again!
2. The engine fan would keep spinning for several seconds after I would switch off the engine.
3. Car would hit 100C, then the aux fans would come on. (sitting in traffic on the highway)
4. In my time with the 300E, I have never heard the fan "roar", it spins, but I just think it has been worn out since I had the car. I have read quite a few threads about the fan clutch, and many people mention that you should be hearing a distinct roar from the fan when the engine is at operating temp.

The fan clutch I removed from my car was a Behr unit, but it appears that it was tampered with. The bi-metallic strip was bent near the middle, and appears to have a dime or some metal disc wedged in it.

So I replaced the fan clutch this morning using the instructions from the factory service manual sheets.

After I buttoned everything up, I started up the car and checked to make sure everything I touched was still spinning true and that no odd grinding noises were coming from the fan clutch or surrounding area.

I left the car to idle for about 3 minutes in the driveway. Then I took her out for a spin around the block. The first thing I noticed is that I can finally hear the fan roar when accelerating. (AWESOME!)

After about 10 minutes of driving in this warm afternoon weather, stopping and accelerating around the neighborhood, the temp gauge never once crossed the 80C mark. (AWESOME!)

Then I remembered a thread on this forum about how Behr viscous fan clutch units are really bad and are generic designs used in tractors and heavy truck engines and are always engaged, even at high RPMS.

To test this, when I was stopped I shifted the transmission to hold 1st gear and accelerated slowly, raising the RPMs to about 4000.
THE NOISE FROM THE FAN WAS REALLY REALLY LOUD.

(NOT GOOD)

So my guess it that the Behr fan clutch really is not good to use with our Mercedes-Benz cars. Peach Parts sells two brands, a Behr unit and an ACM unit. Another vender sells a Behr unit and a Fichtel-Sachs unit.

Should I try the ACM, Fichtel-Sachs or bite the bullet and get one from the dealer?

Above: Tampered Behr fan clutch pulled from car. (Old unit)

JohnM. · #2 04-30-2011, 04:37 PM

BEHR is what came on the car from the factory. It sounds like the one you bought may not have been stored properly. Viscous fan clutches need to be stored upright, not lying down flat.

The fan clutch should roar slightly upon first acceleration on a cold engine, then should go away after first shift. You should not hear roaring again until your engine reaches ~90C. And it should disengage after 4000RPM. Sounds like yours is engaged all the time which will put a lot of stress on the fan clutch bearing bracket, as well as over-cooling the engine.

sptt · #3 05-01-2011, 12:27 AM

I also read something recently on viscous fan clutches and that they are always "engaged" and spinning. I had replaced mine as someone had just glued it solid to the bearing when I originally bought the car and I noticed it never loosened. When the clutch warms up and at higher speeds, they are suppose to "loosen" and still spin pretty fast but not at the same high rpm as it did when it was cold. After I drive my car and get it warm, if I open the hood and sping the fan, it does not spin freely but it is definitely easier to spin vs. being cold (goes about 1/4 to 1/2 turn with a quick flick of the wrist). I bet your clutch is OK.

S-Class Guru · #4 05-01-2011, 12:24 PM

Let me tell you how my 103 fan on my '91 300SE has behaved for the last 20 years.

- I just went out into the 72-degree garage (Rowlett, Tx) and spun the cold fan by hand. It turned maybe 3/4 turn, about 1/2 second, and stopped.
- When the engine is cranked and warmed up to normal temp (85 C) then stopped, the fan can be spun by hand and will turn several revolutions before it stops. It's quite loose at this temp, and will not roar at all when the engine is revv'd.
- Under very hot conditions, when the outside temp is pushing 100, you can occasionally hear the fan roar under initial acceleration, but the roar subsides by the time the car reaches 20 MPH, and is not heard again unless I sit for awhile at a light.

DG

Pili380SL · #5 05-01-2011, 02:58 PM

I keep a summer clutch that is basically always engaged temp wise but not RPM wise. The way I understand it, a different mechanism controls the RPM kickout than the temp "kick-in". It's odd that both functions are inop. As mentioned, it may have been stored inproperly.

dka-66 · #6 05-01-2011, 03:33 PM

Isn't there a South American fan clutch that is available that can be ordered....I also believe there is a write up on how to modify the fan clutch to engage like the
South American one.

Rahulio1989300E · #7 05-01-2011, 04:39 PM

First off, thank you all for your input.

I just got back from an extended ride around town (with the windows all the way down). The clutch appears to have started behaving much better.

Upon first start up with a cold engine, the fan was just barely heard at cold idle RPM levels. When I pulled onto my main street, I accelerated slowly to 30mph, the fan got more audible as the RPMs rose to about 2100 before I had to stop for a stop sign. I kept driving and could hear the fan roaring more as I accelerated, but then after a few signal lights, I could not hear the fan anymore. (Temperature gauge was hovering below 80C at this point.)

So then I started accelerating much more briskly, hitting 3000 to 3500 RPM before shifts, the fan was no longer roaring at all.

I had to stop for fuel and it took a total of 10 minutes as the gas pump was really slow and the receipt printer was out of paper. I had to go in to get a copy.

When I turned out of the gas station' lot, I accelerated slowly and could hear the fan roar for that initial acceleration, but it stopped roaring after every stop and go after that.

Now that I had more confidence in the clutch, I drove to a street with a 55MPH limit and gunned it from a stop sign. 1st gear shift at ~6000RPM, 2nd gear shift at ~6000RPM, fan nowhere to be heard.

So the lesson here, at least for me... even if your fan clutch MAY have been stored improperly by the vendor and appears to be malfunctioning or "always 100% engaged", just double check your installation and drive the car carefully for a bit, give the clutch a few heat cycles, it may start behaving as it should.

Thank You all again for your input.

ps2cho · #8 05-03-2011, 09:34 PM

Wanted to throw my question in here too since we are on topic --

I bought a used Behr FC off ebay (it was dirt cheap)...

Works great, but does not disengage, ever. It is locked all the time. What's the deal? Probably just need a fresh one?

JohnM. · #9 05-03-2011, 09:46 PM

It's all used up! They either fail like that and your engine runs super cool and it sounds like a jet engine under your hood all the time, or more commonly they just free-wheel, and it doesn't cool at all. The exploding metal engine fans on BMWs and other cars are typically due to an always engaged FC.

sptt · #10 05-04-2011, 12:27 AM

It should always be spinning but not roaring after it warms up. I checked my new fan clutch against my daughter's after both were warmed up and they both felt the same cold (tight when trying to spin with hand) and hot (a little looser and more rotation when trying to spin with hand but not free wheeling on the bolt).

Rahulio1989300E · #11 05-04-2011, 03:31 AM

^ This is also what I noticed about my new clutch.

This particular new fan clutch (Behr brand) seems to disengage completely at about 3500 RPM.

The engine is running at 80-85C all day long, no longer does it heat up to 100C in stop and go traffic. I think when I first installed my new clutch it was not behaving as it should, only after driving with it a few times did it at least seem to start working correctly.

I have a feeling that my old clutch was dead the moment I got my car. I NEVER heard the fan roar, cold, warm or hot. I wish I would have gotten to this much more soon, who knows how much damage I have already done to everything in the engine bay including the head gasket with all that excessive heat.

The fan clutch is stiff when I go out to the car in the morning (stone cold engine) and is also just about as stiff after a 45 minute highway drive (just a little more loose).
However, the key point is that you really should not hear the fan at all between a cold engine and a hot engine. The fan should not be engaging during your engine's warm up cycle. My fan seems to start kicking back in around 81-82C, which does actually seem a bit low. (People have said it should only start reengaging around 90C.)

One thing does seem certain and extremely consistent: YOUR FAN CLUTCH MUST DISENGAGE AT AN RPM NO GREATER THAN 4000.

I can actually hear the fan just a little when cruising on the highway at 60MPH with the windows down. I am not sure I should be hearing it, but everything seems stable for now. I really like how the temperature never rises above 85C now.

Certainly, I will be checking for play in the fan bearing bracket very often now as I am still on the original one.

With the old clutch, when I switched off the engine after a 45 minute drive, the fan would keep spinning for at least 6 to 8 seconds.

With the new clutch, it spins for maybe 1 to 2 seconds.

I will keep an eye for changes in my MPG as well. If it drops significantly, that should mean that my clutch is engaging too much or at the incorrect temperatures.

This all makes me wonder just how much variance there is between all of the fan clutches produced.

little_e · #12 05-04-2011, 08:33 AM

I had to replace my fan clutch (M104 '94 E320 Estate). Bought the cheapest I could find. The brand was AVA and it set me back €30. Works like a charm.

ps2cho · #13 05-04-2011, 03:52 PM

Quote:

Originally Posted by JohnM.

It's all used up! They either fail like that and your engine runs super cool and it sounds like a jet engine under your hood all the time, or more commonly they just free-wheel, and it doesn't cool at all. The exploding metal engine fans on BMWs and other cars are typically due to an always engaged FC.

Yeh it sounds like a jet engine all the time....Guess its another thing to add to the list!

At least here in AZ, can't get enough cooling!

sptt · #14 05-05-2011, 02:11 AM

Yeah...you might as well add some wings to that thing!

gsxr · #15 08-15-2011, 01:45 PM

It's interesting how many people are checking their fan clutch by spinning it by hand with the engine off. This is meaningless. It has to be checked with the engine running and at operating temp, and preferably on a warm summer day to ensure the bimetal strip on the clutch is heated. There are basically 3 valid tests:

1) The "roar" test: With the tranny in Park, raise the hood, and slowly rev the engine to approx 3000rpm. The fan should be roaring loudly. If you're not sure, it's probably NOT working correctly. Compare to when the engine is cool (not warmed up yet), on a cool day, to see what it sounds like when the clutch is not engaged. The clutch should disenage by 3500-4000rpm, this is also easy to hear, and when you let the RPM's slowly drop back to ~3000, you should hear the clutch re-engage. The FSM specifies the "roar" test, btw.

2) The "stop" test: When the clutch is engaged, and you shut off the engine, the fan blade should not freewheel or spin at all. It should stop immediately (as shown in this video). If it spins at all (or worse, if it spins for 5-10seconds before stopping!) the clutch was not engaged, and is likely dead. A second person is needed for this test, they turn the key off while you observe the fan blade.

3) The "tach" test: Using an optical tachometer ($30 on sale from Harbor Freight, click here) with reflective tape on the fan blade, and also the drive pulley (not possible on all engines), you can determine if the fan blade RPM is increasing proportionally with engine RPM. If the fan blade remains at a steady speed (300-600rpm or so) as engine RPM increases to 3000rpm, the clutch is not engaged. Some data from my M119 is below, other engines will vary a bit since the crank/fan pulley ratio may not be the same, but you get the idea:

Car #1 - Bad Clutch:
With the engine at ~650rpm idle in park, pulley speed was ~810rpm, actual fan blade speed was ~275rpm (only ~35% lockup).
With the engine at 1500rpm idle in park, pulley speed was ~1900rpm, actual fan blade speed was ~500rpm (only ~25% lockup).
With the engine at 2500rpm idle in park, pulley speed was ~3200rpm, actual fan blade speed was ~500rpm (only ~15% lockup).

Car #2 - Good clutch, NOT engaged:
With the engine at ~650rpm idle in park, pulley speed was ~800rpm, actual fan blade speed was ~325rpm (~40% lockup).
With the engine at 1500rpm idle in park, pulley speed was ~1900rpm, actual fan blade speed was ~410rpm (~22% lockup).
With the engine at 2500rpm idle in park, pulley speed was ~3100rpm, actual fan blade speed was ~980rpm (~32% lockup).

Car #3 - Good clutch, engaged:
With the engine at ~650rpm idle in park, pulley speed was ~800rpm, actual fan blade speed was ~775rpm (97% lockup).
With the engine at 1500rpm idle in park, pulley speed was ~1900rpm, actual fan blade speed was ~1750rpm (92% lockup).
With the engine at 2500rpm idle in park, pulley speed was ~3200rpm, actual fan blade speed was ~2600rpm (81% lockup).

YMMV, etc...