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  #1  
Old 05-26-2009, 12:19 PM
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Location: Portland, Oregon
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Fan Clutch Fiasco - What to do next??

Hello from the beautiful Pacific Northwest!

My car has been running a bit hot lately and normally stays in the 80-85 temp range. Classic scenario of running cool on the highway but running hot on hills and in traffic (near the 95 – 100 temp range)

I tried all the easy fixes first, coolant flush/change (zerex G05), new Behr thermostat, new expansion tank cap, ran the car with the cap off to try to get any air out of the system, etc.

Next step I get a new fan clutch installed. Went with the German made aftermarket APA version. It fixed the problem. Temp dropped back to normal, car was running cool again (highway/city/hills) and the slight flutter on the oil guage (due to the heat) stopped and the oil pressure increased back to normal. All seemed OK.

Driving home 2 days after the repair, I hear a metallic ping sound coming from the engine compartment. Apparently the cover on the small rectangular piece (see pic link at bottom of page) on the front of the APA fan clutch came loose and was thrust into the radiator at such velocity from the fan that it punctured a large hole in the radiator, tore a small piece off one of the fan blades and I lost virtually all of the coolant.

Surely this is a freak occurence and rarely happens …. But it happened.

The repair shop (a very good and honest independent) accepted responsibility for the part failure and replaced the APA with the OEM Sachs fan clutch, new Behr radiator and fan. They covered the cost of the new radiator and fan, flat-bed towing, etc., I had to pay the difference for the Sachs fan clutch (approx $300.00 more than the APA).

Now….. the temps are back up to 95-100 range on hills, 90-95 range in city driving and don’t drop down very quickly once I get back on the highway, but sometimes they do and sometimes they don’t. In addition, I can get the temps to drop a little bit by turning on the defrost to get rid of some heat (??).

Some observations:

The old Sachs fan clutch that was replaced with the APA had low resistance when doing the spin blade test (turning the blade by hand at cold and hot operation). It would move fairly freely (5-6 blades). In addition you could easily stop it with a towel with the car running (another test I read about on this site).

The “new” Sachs fan clutch acts exactly the same as the old one! Low resistance and stops easily! (Was my fan clutch even the problem??)

The aftermarket APA fan clutch had very high resistance when doing the spin blade test, maybe a half a blade movement and I would not attempt to stop the blade by towel while running (test).

So, final analysis… New Behr radiator, Sachs fan clutch, fan, Behr thermostat, radiator cap, coolant (zerex G05), air bubble removal.

My line of thinking it to get the Sachs fan clutch out and go with another APA aftermarket version, in my eyes APA appears to operate better! The rectangular cover came off by a freak accident, and a pair of needle nose pliers prior to installation could simply tighten down the small rectangular housing that holds the cover. See this link for pictures:

http://www.thebenzbin.com/parts/?N=11172+4294963907+1668+9363

Any advise or recommendations greatly appreciated!


Brian
Portland, OR

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  #2  
Old 05-26-2009, 12:41 PM
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Brian,

THe fan clutch suppose to turn easily- UNTIL it reaches 105C. It isn't clear in your discussion if you are turning the clutches HOT or just fiddling in the engine compartment.
Does the new fan clutch engage properly?? It should be apparent. The factory ones have been known to be DOA to.

M
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  #3  
Old 05-26-2009, 01:08 PM
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Have low aux fan when a/c is ON ????
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  #4  
Old 05-26-2009, 06:38 PM
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Fan Clutch Fiasco

Aux fans work properly when AC is on.
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  #5  
Old 05-26-2009, 08:16 PM
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The fan clutches that I have bought (Behr) have a warning to NOT store them laying down, only standing up. Could this be part of the failure/issue?
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  #6  
Old 05-26-2009, 09:23 PM
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fan clutch adjusment

The fan clutch can be adjusted to kick in earlier. the rectangular bi-metal plate on the front can be raised by one mm ,this raises the piston pin up and the fan will operate at around 90 C. easily heard to activate in and off by the roar of the blades.
mak
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  #7  
Old 05-26-2009, 10:13 PM
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The fan clutch on my W114 started going bad again (I've replaced it before) and I decided I wasn't going to pay the $100 plus for a new one again. For less than the amount of the clutch I bought a 16 in. (2600 cfm) electric fan to replace the one in front of the radiator and hooked it up so it comes on as stock (210F degree switch) and also anytime the A/C compressor is on. I ditched the stock fan clutch and got a adjustable, thermostatically controlled 14 in. (2100 cfm) to replace it. I just finished it today and haven't driven it too much yet. I've tried it with and without the A/C (85 degrees here today) and it is running about 190F in stop and go driving. If you don't mind deviating from stock this may be the way to go.
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  #8  
Old 05-27-2009, 01:01 PM
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Fan Clutch Fiasco

In reply to all that responded... Thank you!

I guess it is possible that the Sachs (OEM) replacement clutch is bad.

I have also heard about the mod of removing the clutch and working on the actuator pin... but what I was told over on benzworld was to remove 2mm as opposed to increasing it.

Bottom line - The APA aftermarket clutch seems to work prefectly provided the cover on the front rectangular housing does not come loose.

Is there any definitive opinion on which clutch works the best - Sachs OEM or the APA aftermarket.

Thanks again for the replies.

Brian
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  #9  
Old 05-27-2009, 02:36 PM
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My (electric) aux fans ground to a stop last week; while waiting for the new motor to come from CA I noticed the engine gets scary hot quite quickly even when I tried to avoid stop n go traffic. I tested the engine fan's clutch and discovered it didn't work! we really needed the car so I wrapped a piece of thick string around the clutch to cause enough interference w/the pulley that it runs all the time. Problem solved. If you try this it is tempting to do it by tyeing the string to a fan blade and startin' her up and while this would be the fastest way if it worked I strongly recommend the engine OFF method.

I KNOW MB wouldn't put the mechanical fan on the car unless it was necessary but it seems like a backup fan to me - the electric fans do most of the work.

-Tom
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Old 05-27-2009, 03:00 PM
CWW CWW is offline
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Quote:
Originally Posted by bjflatley View Post
In reply to all that responded... Thank you!

I guess it is possible that the Sachs (OEM) replacement clutch is bad.

I have also heard about the mod of removing the clutch and working on the actuator pin... but what I was told over on benzworld was to remove 2mm as opposed to increasing it.

Bottom line - The APA aftermarket clutch seems to work prefectly provided the cover on the front rectangular housing does not come loose.

Is there any definitive opinion on which clutch works the best - Sachs OEM or the APA aftermarket.

Thanks again for the replies.

Brian
Adding washers to raise the bi-metal strip by a couple millimeters is the same thing as shortening the length of the actuator pin. Just two different methods of achieving the same thing, it will work the same either way.

With either method, what you're doing is causing the end of the actuator pin to pull out and engage the clutch earlier in the temperature range. As they say; it's "12 of one and a dozen of the other".
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  #11  
Old 05-27-2009, 03:10 PM
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-Tom
>

Just the opposite. The vicscous IS the Main fan and it moves air even when not locked up.
The aux fans are just that... Auxilary Fans..they only come ON when there is a Higher than normal Thermal Heat Load. If the main viscous is operating as designed , there is no need for aux fan except when the system is burdened with extreme heat load or a/c high pressure at condenser .
If all systems are normal and ambient temp do not present a high load , the aux fans will never come on bc they are not being called for.
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Old 05-27-2009, 09:41 PM
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Wrapping a string or otherwise locking the fan on is risky, the fan is not designed to run the full RPM of the engine, could pull a BMW and come apart at high revs.
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  #13  
Old 05-27-2009, 09:46 PM
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Yes...those vicscous cut out @ 4200-4500 rpm...it aint gonna do that locked up with a string aound it. Right thru the hood...or rad..........
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Old 05-28-2009, 10:02 AM
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I considered that but my wife probably hasn't ever revved past 3000, and I seldom do. I warned her in case she decides to start now. I also respectfully disagree with the opinion that the fan couldn't spin the full redline of the engine without grenading.
What's inside the clutch? Has anyone had one apart? Is it like a torque converter, two sets of vanes? It must be a more total lockup or else the spin-the-fan-while-the-engine's-hot clutch diagnostic wouldn't work. I wonder how it could possibly decouple at a certain RPM? A couple governor weights could open a valve I guess. I still think it spins right along, though.
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  #15  
Old 05-28-2009, 10:14 AM
CWW CWW is offline
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Quote:
Originally Posted by babymog View Post
Wrapping a string or otherwise locking the fan on is risky, the fan is not designed to run the full RPM of the engine, could pull a BMW and come apart at high revs.
Who does THAT? That just sounds like a disaster.

What we're talking about is shaving a couple of millimeters off the actuator pin, or putting a washer under the bi-metal strip to raise it a couple millimeters. A 2mm reduction in the inserted depth of the actuator pin, either by raising the bi-metal strip or by shortening the pin itself, is good on the OEM sachs clutches for around a 10c reduction in engagement temp. The high-rpm cutoff still works as it should, as does the rest of the clutch.

The only thing you're changing is the engagement temp. Certainly nothing unsafe about it, and you're not "locking" the fan, it still engages and disengages as it should, just at a lower temperature. The factory setting is around 100c, so by the time the fan is fully engaged the car is already running hot. Lowering it helps your operating temps, as well as your a/c performance.

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