Fan Clutch HELP.. - PeachParts Mercedes-Benz Forum

Merc1 · #1 07-28-2003, 07:16 PM

Hi,

I did do a search, like a good boy.

I was at a mechanic today, for Crankshaft Damper replacement. He noticed the blade are not turning by hand. He said Fan clutch is bad.

He is not an exclusive MB mechanic, so.. I told him I will get back to him after I consult real MB knowledgable people here.

Here is the fact.

I drove the car to the shop, car was off for 20 minutes, he was taking out the fan shroud, and noticed fan was not spinning freely.

He said fan is on all the time.

1. Should I worry about it?
2. Can this be fixed, I read post about adding Toyota fluid.. or should I just change it.

3.Or is it normal for the fan to turn with the car running.
4. what is the procedure if change needed.

Thanks,
1998 E 320 75k

JimSmith · #2 07-28-2003, 08:11 PM

Merc1,

I doubt your clutch is failed. The more prevalent failure mode is to have the fan fail to turn with the engine even when the engine is hot enough to have activated the clutch, not lock up. If you check the car first thing in the morning after it has had a chance to cool you should get more representative results. Start the car, let it run for a minute or so, then shut it off and see if the fan blades turn by hand.

In reality the fan blades should be hard to turn when the clutch is engaged, but not impossible. It is a fluid clutch (unless your vehicle has an electromagnetic one, in which case I am not sure of its behaviour with the clutch engaged and the motor not running), and the design limits the torque the clutch can transfer, which limits the speed of the blade wheel. So, when engaged it runs like it was locked up until the engine rpm gets over about 2500 or so, when it begins to slip a bit. By 3,000 rpm the clutch reaches its maximum torque transmission limit and the fan will not speed up when the engine speed increases.

I hope this helps. Jim

cbdo · #3 07-28-2003, 08:24 PM

Having browsed considerably about fans, my first question would be whether you're getting any problems with engine temp control. If not, I'd take some convincing that there's anything that needs replacing.
My own issue was simply the sound of the fan; see thread on The Howling. The viscous clutch on my 560SL allows the fan to be turned fairly easily by hand with the engine off, but there's no trouble keeping temp within spec in stop-and-go traffic at 85F ambient.

JimSmith · #4 07-28-2003, 08:33 PM

cbdo has a point. There are people concerned with overheating that have proposed schemes to try to get their fans to turn all the time by defeating the clutch altogether with some mechanical device, or filling the clutch with fluid, completely, and using a higher viscosity fluid (apparently available from Toyota in 18ml bottles). So if your engine is running cool enough the clutch is probably ok. Good luck, Jim

Merc1 · #5 07-29-2003, 12:59 AM

Jim Smith and cbdo.

Thanks, for lengthy writeup.

My temp is great, 84 C in local traffic.

When I stop at light and move, I feel lots of Fan air, like I am pressing more gas. But in reality it is only runnung at 2k rpm.

I let the car cool, than started, fan is turning and it is engaged. Like cbdo said earlier, howling wind sound...

I hope I am explaining it right, please tell me what should I do, so I can report here afterwards.

I like the fan running, it keeps the eng. temp lower, however, I want Mercedes to be in perfect condition.

HEEEEEEEEEEEEEEELLLLLLLLLLLLLPPPPPPPPPPPPP.

sixto · #6 07-29-2003, 02:42 AM

A 98 E320 running at 84C all the time seems too cool to me. The newer cars tend to float around 100C in traffic with the AC going. Check out JimF's website at http://pages.prodigy.net/jforgione/MB_S500.html Could be that your fan failed in a manner similar to the bimetal strip mod Jim proposes.

My concern would be that the fan is not disengaging as it should at higher engine revs. It might not be balanced at higher revs. I'm no engineer... well I do have an engineering degree

... but I suspect that fans that depart from the pulley and make a meal of the radiator are fans in which the clutch locked up.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

cbdo · #7 07-29-2003, 09:45 AM

Sixto raises an important point. The fan system is intended to have a max RPM significantly lower than engine speed. Review the attached link for a discussion of fan motion; bear in mind their problem is different from yours, but the discussion is applicable if you've got a viscous-fluid fan drive.
Clutch Fan on 300D 124

Merc1 · #8 07-29-2003, 08:29 PM

Fixed it.
Parts $135 Fan clutch.
Changed in 10 minutes.

Ok..here it is, problem with the fan clutch was the bearing behind the nut were jammed and it was visible only after removal, apparaently the bearing got jammed inside the clutch. After taking the radiator cover off, I noticed a wobble in the fan. This was not visible with the fan shroud on.

Now my car doent run like a JET taking off :p

Now my temp is back to where mercedes intended around 96 C.
before when the fan clutch was engaged all the time it was 86 C.

I like to run the cooler engine personally I like below 90 C. I ordered a part from radio shack a small resister it is very easy to install anto the 1 of the temp switch it will drop my temp by 10 C.
It will allow the 2 fans to come on early, thus cooling before 95 kicks in.

Hope this helps with fan clutch problems.

#9 07-29-2003, 11:48 PM

Good job!!!

sixto · #10 07-30-2003, 12:18 AM

Make sure you check your references in installing that resistor. Early 140s have an independent temp sensor for the auxiliary fans. Late 140s share the temp sensor between the fans and the ECU. The fans will come on sooner but the ECU will be working off erroneous information. Make sure such is not the case with your car.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Merc1 · #11 07-30-2003, 01:19 AM

Quote:

Originally posted by sixto
Make sure you check your references in installing that resistor. Early 140s have an independent temp sensor for the auxiliary fans. Late 140s share the temp sensor between the fans and the ECU. The fans will come on sooner but the ECU will be working off erroneous information. Make sure such is not the case with your car.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Thanks sixto, mine is 1998 w210 ( e320) What do you think, I read on jim's page about it and thought about it. My temps are running at 92-95 F.

Is this good or should I install resistor on TC switch.

Thanks

Southern · #12 07-30-2003, 10:19 PM

Merc 1,

Your car was designed to run between 90 - 95 Deg. C. I would not recommend that you artificially lower the operating temperature of the engine. A engine running at the designed temperture will burn off any moisture, get better gas milage, and put less load on the fan motors.

JimSmith · #13 07-31-2003, 08:54 AM

I believe the design temperature for normal operation of the car is closer to the 86*C figure than the present 96*C figure. When you are running with "excess" cooling capacity the engine temperature is regulated entirely by the thermostat. If, under those conditions the water temperature is 86*C, then that is what was intended for the engine coolant temperature.

When the heat load under other conditions exceeds the capacity of the system these fans come into play. This is normally not an issue as at highway speeds the air flow through the radiator without the fan should be enough to keep the system in the thermostat's regulation range. When you stop and idle in traffic, the fans are needed to regain some heat rejection capacity lost by the lack of air flow over the radiator surfaces. A higher water temperature will increase the effectiveness of the radiator as well, so the temperature stabilizes at a higher value.

If you have heating issues at speed, the thermostat is more likely the problem, assuming the fluid levels are correct. But an engine running with the coolant temperature being regulated by the thermostat is what was intended, and if the thermostat does that at 86*C I would not classify that as cold. I would call the 96*C value "hot" and, by the words in the manual, I would not consider it too hot. But I would be more comfortable with the 86*C number.

Good luck, Jim

Merc1 · #14 08-01-2003, 01:51 AM

Jim

I agree, However, I noticed other people's car running in Arizona around 95-97 C in local traffic.

My car does the same in local, however on highway it runs around 90 C. Keep in mind its hot here in AZ usually around 108 F.

1. Now based on the above info, do you still think I need to change my thermostat?

Also, I heard MB make several temp Thermostat.

2. Can you please guide me which one is best for this climate and my car.

3. How would I go about installing it, any tricks or gasket, sealer..etc.

98 e320
Thanks