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  #1  
Old 11-13-2007, 01:31 AM
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Fan Clutch and overheating

Hi There,

I have been having some overheating (95 - 100) on my car and was planning on checking the compression this weekend.

This evening, as I went to get on the freeway, I had a sense that my car had gotten to operating temperature a little quickly and when I accelerated onto the freeway, a giant cloud of smoke came out of my exhaust. Then, the car got awfully hot (110 -112) and I had to drive 50 mph to keep it at 95-100. I pulled off the freeway and got back home.

When I inspected my engine, the fan seemed to be seized. I was able to loosen it and then it spun when I started up the engine. When I stopped the engine, I noticed that the rear flange of the fan clutch was wobbling - almost as if the sleeve for the shaft had broken.

The clutch and the fan are now separated and sitting on my work bench. It looks like this clutch is sealed and there is no way to open it up but that rear flange wobbles and it feels like the shaft in the clutch is catching on something - it definitely does not feel like there is any oil in there.

This is the model:
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2851CSQGG2851CSZJ6&year=1982&make=MB&model=300-TDT-001&category=G&part=Fan+Clutch

The thing that I am confused about is that it would seem that a problem with the clutch would cause me to overheat when I was going slow, not when I was going fast.

I have 3 main questions:

1) Is it possible that the clutch and the sudden freeway overheating are 2 separate issues and not related? I checked the radiator and it doesn't look damaged.

2) Is there any chance that this might have hurt my crankshaft? It seems to be spinning fine when the fan and clutch are off.

3) Is it possible to open up the clutch on this model and see if there is internal damage?

As always, thank you in advance for any help,
Sasha

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  #2  
Old 11-13-2007, 01:42 AM
ForcedInduction
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The fan only cools the engine at low speeds. The natural airflow over the radiator cools the engine on the highway.
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  #3  
Old 11-13-2007, 02:28 PM
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Have you ever had your clutch out? Should the flange be spinning smoothly or does it wobble a bit?

Sasha
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  #4  
Old 11-13-2007, 02:44 PM
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What was the temperature outside at the time of the overheating? I suspect that the fan clutch is a seperate issue and I would be concerned about the giant cloud of smoke that came out of the exhaust.

Last edited by johntksr; 11-13-2007 at 03:42 PM.
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  #5  
Old 11-13-2007, 03:22 PM
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Fan clutch is not rebuildable far as i know. One died on my 280/8 and resulted in car running hotter than normal but never entirely over-heating. In this regard your symptoms fit bad fan clutch.
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  #6  
Old 11-13-2007, 03:44 PM
Craig
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A bad clutch will cause high temperatures in traffic, not at highway speeds. I would replace the clutch, but I think you also have something else going on.
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  #7  
Old 11-13-2007, 04:05 PM
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gimme a low-tech 240D
 
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From what i've seen based on experience bad fan clutch effects overall cooling efficiency under all everyday driving conditions. But can understand how 'theorists' here would assume it relates only to standing still in traffic.

Meanwhile I'd attack the water pump next. Alot of people dont realize it but water pump cast pig-iron blades can slooowly corrode and wear down to nubs. Water pump probs can be alot more insidious than you think. It aint like they necessarily run at 100% efficiency 50-60k miles then suddenly die instantaneously.

Whats important is you've got handle on situation from the git-go noticing car warms up and runs hotter than normal but you're smart enough not to let it entirely overheat. Yep, I'd throw new water pump and fan clutch into the car without hesitation. Specially with fan already pulled and being halfway there to installing $50 water pump. Fan clutch on the other hand, gonna be somewhere around $125 unless ye got junkyard nearby.

Last edited by 300SDog; 11-13-2007 at 04:26 PM.
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  #8  
Old 11-13-2007, 04:29 PM
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Dieseldog makes a good point about the water pump. It's been 60k since my last change, so time to do it again. In addition, with the engine off, you should be able to turn the fan but with resistance. If you don't feel this resistance or if the fan turns with great difficulty, the clutch is bad. I, too, know of no way of rebuilding the fan clutch - at least in my home garage.
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  #9  
Old 11-13-2007, 04:53 PM
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Quote:
Originally Posted by DieselDog View Post
From what i've seen based on experience bad fan clutch effects overall cooling efficiency under all everyday driving conditions. But can understand how 'theorists' here would assume it relates only to standing still in traffic.

Meanwhile I'd attack the water pump next. Alot of people dont realize it but water pump cast pig-iron blades can slooowly corrode and wear down to nubs. Water pump probs can be alot more insidious than you think. It aint like they necessarily run at 100% efficiency 50-60k miles then suddenly die instantaneously.

Whats important is you've got handle on situation from the git-go noticing car warms up and runs hotter than normal but you're smart enough not to let it entirely overheat. Yep, I'd throw new water pump and fan clutch into the car without hesitation. Specially with fan already pulled and being halfway there to installing $50 water pump. Fan clutch on the other hand, gonna be somewhere around $125 unless ye got junkyard nearby.
I was thinking water pump as well...and as stated much easier with the fan clutch removed.
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  #10  
Old 11-13-2007, 05:12 PM
Craig
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Quote:
Originally Posted by DieselDog View Post
From what i've seen based on experience bad fan clutch effects overall cooling efficiency under all everyday driving conditions. But can understand how 'theorists' here would assume it relates only to standing still in traffic.
I've replaced two worn out fan clutches on my 300D over the last 250K miles. In both cases, highway temperatures were normal but it heated up rapidly in traffic. In both cases replacing the clutch fixed the problem. You could drive at highway speeds with the fan removed and have normal temperatures.

I wouldn't bother with junkyard clutches, even the new ones wear out too quickly.

BTW, you still have something else going on, a "giant cloud of smoke" and rapid temperature increase are not symptoms of a bad clutch.
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  #11  
Old 11-13-2007, 06:07 PM
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OK, I will definitely replace the water pump and the clutch. It seems to me that the smoke could have been caused by a sudden overworking of the engine.

I have had the car for about 50,000 miles and have not replaced the water pump.

Since I have so many helpful members checking out this post, maybe you can clarify something for me. I have the following symptoms:

1) I am getting some overheating
2) My rear injector seems to sounds different on every 4th stroke (I don't know the right word for that, the series of intake, outtake, compress, inject)
3) I am idling rough - but only intermittently. More often when the engine is cold but also when the engine is hot. If I give the engine a very little bit of gas, it settles out. Sometimes the roughness manifests itself as a surging and sometimes as a loping or lulling. (Not sure if that is the correct word)
4) Sudden difficulty starting the engine when cold. I have checked the glow plugs at the relay and they seem good.


Before I realized the fan/water pump problems, I was living in fear of a head gasket replacement. If the waterpump/fan replacement doesn't fix the problem, does that sound like a valid concern?

Here are some things that I am thinking about doing to figure out the problem(s):
- Checking compression (Valves were adjusted 100 miles ago)
- Messing with the rack damper pin
- Doing another diesel purge (The first purge seemed to work well, c
- Flushing the cooling system

Probably in that order.

Hopefully, I am not taking this thread too far off topic but my car is trying to tell me something and I want to take care of it.
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  #12  
Old 11-13-2007, 06:10 PM
Craig
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It sounds like you are on the right track. I would do the compression check to rule out any major problems that could explain the cold starting issues.
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  #13  
Old 11-13-2007, 06:13 PM
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I'd throw a new thermostat in before I'd consider a water pump replacement as being necessary. A lazy thermostat can cause the overheating symptoms you describe and it is far easier and less costly than a water pump would be...just my $0.02.
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Old 11-13-2007, 06:14 PM
Craig
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Originally Posted by nhdoc View Post
I'd throw a new thermostat in before I'd consider a water pump replacement as being necessary. A lazy thermostat can cause the symptoms you describe and it is far easier and less costly than a water pump would be...just my $0.02.
Good point, my water pump has over 250K miles without any issues.
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  #15  
Old 11-13-2007, 06:21 PM
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Ruling out Head Gasket

I have read alot of posts about compression and head gaskets. Just to clarify, if the compression is pretty good and even on all cylinders, that pretty much rules out a head gasket, right?

Or are there exceptions to that rule?

(I have a thermostat that I was planning on installing so I will do that as well)

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