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  #1  
Old 01-10-2003, 03:11 PM
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300SDL Fan Clutch - Possible Replacement

After searching through the archives, I think my fan clutch is finally in need of replacement.

Last summer, the car ran hotter than I'd like to see when pushed hard or when idling for an extended time. It would get up to 105, sometimes even 110, but as soon as I was moving normally again, it went back down. The radiator is new(er) and I have about 10k miles on MB coolant and thermostat.

Since it is cold here in Illinois, the car never sees above 90C regardless of how long it idles or how hard it is driven.

First off, when the car is at operating temp, the fan appears to still turn rather slowly. Also, it spins freely for a few seconds when the car is turned off. I've never heard the fan "kick in", even if the aux fan is running full bore. In fact, even when the aux fan is on, the big fan looks to be running at the same slow speed as always.

Any suggestions? Also, any tips at replacing it would be appreciated.
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Lance Allison
Lance@LanceAllison.com

Sold: 1987 MB 300SDL, 320k miles, Astral Silver, Blue Leather, all books and records from day one.

Totalled: 1998 VW Jetta TDI, 488k miles, Classic Green/Gray Leather, loaded, E-Codes, "Slightly" modded, "Slightly" faster than stock, arrived 11/07/1997.

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  #2  
Old 01-10-2003, 04:59 PM
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Sounds like my fan hub which also needs replaced. Look in Fastlane they sell just the hub for about $150 I think.
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  #3  
Old 01-10-2003, 09:11 PM
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Lightbulb

Lance, I had the same problem last summer. After much reading on this site, I found that the easiest way to test the fan clutch is as follows: First, you have to get the engine temp up to 100-105. Stop the car and open the hood and watch the fan as your helper turns the engine off.(Keep your hands away from under the hood!). The fan should stop about as fast as the engine. If it free wheels alot, the fan clutch is bad. Second, with the engine still hot and the engine OFF, try to turn the fan . If the fan turns easily, the fan clutch is bad. I let an independent shop fix it because the space is so tight between the fan and radiator. That fixed the over heating problem. (I could never figure out the aux fan. It seemed to have a mind of its own, so keep your fingers away from it at all times.) By the way, my owner's manual states that it is OK if the temp goes up as long as it does NOT reach the red (over heat) part of the gauge. Please, everyone, I don't want to debate this issue, I'm just saying what the book says!
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Last edited by PaulH; 01-10-2003 at 09:17 PM.
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  #4  
Old 01-10-2003, 09:14 PM
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I'm sure you have a bad fan clutch, replace it.

I think it simply bolts on in the normal fashion, unlike the M013 fan that has a single bolt in the center -- that one takes two special tools.

As long as the needle doesn't go into the red zone, you are fine. If it does, it can be BIG trouble, though!

Peter
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  #5  
Old 01-11-2003, 11:19 AM
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I feel your pain man!

I get the joyous job of replacing the belt and tensioner on my 300D next week -- my brother was driving it (long story) and heard the belt squeaking -- took a look under the hood and found the tensioner spring in two pieces!. Not much point in not replacing the belt at this point, since I've been hearing intermittant squeaks since last year, and I've been told it is vastly easier and faster to weasel the belt out around the fan than it is to take the bloody thing off!

We will see.......

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #6  
Old 01-11-2003, 05:57 PM
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Replace the tstat with another one first .... see if fixes it ... they are notorious for being faulty.
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1991 350 SDL (200K and she ain't bent, yet)
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  #7  
Old 01-12-2003, 03:21 PM
300SDL
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I have a extra used fan clutch that i bought for my 300sdl and ended up not needing if you are interested it yours for what i paid $60,
Bobby
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  #8  
Old 01-12-2003, 03:29 PM
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Dieseldiehard,

Cut a piece of thin pressboard or good cardboard to the inside dimensions of the radiator and just duct tape it in to protect both your hands and the rad. fins when working on that side of the rad. FWIW
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  #9  
Old 01-12-2003, 11:03 PM
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007

Now that is a good idea!
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  #10  
Old 01-12-2003, 11:10 PM
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try replacing the tstat and fan switch first ($20 each) before replacing the fan clutch. on 201 clutch almost never goes bad, and replacement is PITA (need to press it on).
I replaced 3 bad fan switches since 2000 (after paying $290 to replace a perfectly good fan clutch).

BTW, the switch still may be bad even if the aux fan kick in. BUT if the car runs hot under load it CANNOT be fan clutch. The electric fans should not come on at highway (over 45 mph) speeds. how's about a water pump or an air bubble. also, did you check your temp sending unit????
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  #11  
Old 01-13-2003, 09:01 AM
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Lance,

A mechanic told me an easy is to see if a rag will stop the fan (at idle!) The bearings in mine were old and it would wobble a bit, so I replaced it. But, it made NO difference in temperature. Sitting with the A/C on in the summer, and it will start to rise in temp, or at lower speed with high load. As soon as I move on the highway, its 90C. My rad was replaced, etc with no difference. Sounds like we have the same symptoms, and you have a new head... I also note that my car will sometimes run COOLER in hot weather (on the highway). Between 50-57 and 30-35 it seems more likely to run 95C than 90C. Let me know if you 'solve it'.

Brian
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  #12  
Old 01-13-2003, 09:03 AM
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Lance,
I had similar symptons last year with mine. I did the test suggested by Paul, I also searced the archives and determined the fan clutch was not working properly. The thermostat replacement would have been cheaper and easier. I removed the radiator and had it checked while I replaced the clutch. Changing it with the radiator in place looked like a real difficult job.
Tom
'82 SD
'86 SDL
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  #13  
Old 01-13-2003, 06:37 PM
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I've dealt with this on several 603 engines. It sounds very much like the fan clutch is the problem, although it is possible that your new radiator could be plugged again already from gunk in the system (not likely, but NOT impossible! I had a new dealer radiator fail (plugged internally) in less than 4 years / 40kmi).

As to operating temps, with a perfect cooling system it should almost NEVER exceed 100C and even then maybe only get to 105C. The electric fan kicks on high speed at 105C, btw, but it is NOT enough to cool the engine - the mechanical fan MUST be working too. I replaced the fan switch as mine was not working (the fan didn't come on above 105C, this was cured with a new switch.) The final cure for my hot running was new radiator & fan clutch. Now the engine refuses to go above 100C, ever, under any conditions so far including 110F ambient temps with the A/C on max, idling, climbing hills, whatever.

If your fan has metal blades, the clutch is probably original and should be replaced. If plastic, it may be a newer clutch, but that still doesn't mean it's working properly. The test methods described above should give you an idea if it's working but from what you said, I don't think it is engaging!

The fan & clutch can be removed with the radiator in place with these tools:


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  #14  
Old 01-13-2003, 09:25 PM
turbodiesel
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Holy crap, the water pump pulley holder tool is $83?!
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  #15  
Old 01-13-2003, 11:00 PM
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DDH,

Nope, haven't popped in there yet. I probably will sometime to check them out though!

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Boise, ID

1997 E420 - 155kmi (Bugeyes)
1994 E420 - 145kmi (Blondie)
1993 500E - 193kmi (Lollipop)
1992 400E - 189kmi (Stinky Dirty)
Check out my website photos, documents, and movies!
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