need to replace the viscus

[allerston]

hello all , the viscus fan on my car is to tight, it does not spin freely when i try and spin it by hand and i cannot seem to fine a viscus with 3 studs,will it be a problem if i use a viscus with the 4 studs .and which way do i loosen it.

i would really like to know how is works.

thank you

[632 Regal]

counter clockwise will unscrew it, not sure about the 3 to 4 stud ordeal...

[shogun]

the visco clutch should not spin free when it is hot/warm, that is a sign that it WORKS properly as it should. It spins free when it is cold or defective.
And no, you cannot replace it against one with different number of bolts, because some models of BMW engines have visco clutches with 3 bolts and others 4 bolts, and the diameter is different as well as the fixing point of the fan , 3 or 4.

The first signs that a clutch fan is failing are obvious: The engine starts running hotter and a/c performance drops. To confirm the diagnosis, start with this simple test: Spin the fan as hard as you can on an engine that has not been started that day. If the fan rotates more than five times, you can bet the clutch is bad. You should feel some resistance and the fan may spin up to three times, depending on the ambient temperature. But even if it rotates three or fewer times the clutch could still be bad. You need to do more tests.

BAD CLUTCH
If your fan clutch is not operating the way it should, it's likely due to a fluid leak or a bad thermostatic spring or valve.

When a leak occurs, it's at the bearing seal, at the center rear of the clutch. Run your finger around the joint and if you get a big dollop of black goo, that's silicone fluid that has leaked from the housing. Replace the fan clutch. A light smear of silicone fluid could be normal seepage--no seal is perfect. Obviously, if a substantial amount of fluid is missing, the clutch won't spin as fast as it should.

As for the other potential culprit, most failing thermostatic springs open the valve too soon. This premature clutch engagement means the fan spins faster than it should, but that doesn't make the engine or a/c run hot. On the other hand, failed valves that stick closed result in low fan speeds and little cooling.

HOW HOT WAS IT?
Let's say spinning the fan didn't reveal a problem, there's no leak and you think the spring is okay. You could still have a bad valve. Here's how to find out. You'll need to test the temperature of the air moved by the fan using a probe-type thermometer that reads to at least 220° F, preferably to about 250° F. You can't use an infrared thermometer because it will read the temperature of a nearby surface, which could be very different from the air temperature. Find a joint in the fan shroud with enough flex to let you insert the probe without getting it in the path of the fan. If necessary drill a small hole in the shroud. Run the engine at fast idle. Check the engine temperature gauge or your scan tool. If it's a hot day, the coolant temp will rise. As it approaches 200° F, you should hear the fan noise rise to a mild roar and see the fan spinning a lot faster. Air temperature in the shroud should remain in the 150° F to 190° F range. There are some exceptions--for instance, there are Chrysler products that may have a clutch fan rated at up to 205° F. Note: Don't try to take an instant reading. A conventional thermometer, even the probe type, takes at least a couple of minutes to stabilize.

If you don't have a thermometer, you can hear what you need to know. Listen to the fan noise with the engine cold, then warm up the engine. Watch the temp gauge. As the coolant nears 200° F, you should hear the noise increase as the fan engages and starts pulling a lot of airflow. If ambient temperatures are cool, cover the front of the grille with cardboard to block the flow of air through the radiator and to help raise the coolant temperature (leave the a/c off). As the coolant gets hot, fan noise should increase to a roar and the fan should spin a lot faster. If not, you'll need a new clutch.

http://www.popularmechanics.com/how_...22.html?page=2

How Car Stuff Works

The fan clutch is an automatic device that is often used in a vehicle’s cooling system. So, when the engine is cool or even when it is at a normal operating temperature, the fan clutch will partially disengage the engine’s radiator cooling fan (which is mechanically driven).

This is normally found at the front of the water pump and it is driven by a belt and pulley that is connected to the engine’s crankshaft. This process will then save power because the engine won’t have to fully drive the fan.

But, if the engine’s temperature gets hotter than what the settings for the clutch are, the fan will then become fully engaged, this will then maintain or even lower the temperature of the engine.

You will find that most fan clutches are viscous or “fluid” (the internal friction of a fluid that is produced by movement of its molecules against each other. It is what causes the fluid to resist flowing) couplings that are combined with a bi-metallic (it’s a strip that is used to convert a temperature change into mechanical displacement and it usually consists of two layers of iron and copper) sensory system that is similar to that in a thermostat.

Sometimes fan clutches will fail on you but they are normally quite reliable so this doesn’t often happen. You will find though that a common symptom of the clutch fan failure is the car overheating when idling.

If you have a bad fan clutch, it can also cause very poor performance in the vehicle’s air conditioning system. The reason for this is because the fan also cools the air conditioner’s condenser and that is found directly in front of the radiator.

The other potential symptom if the fan clutch fails is that it will draw the air at a very high rate, so in the cold weather the heating system will blow out lukewarm air and it won’t ever deliver enough sufficient hot air.

It is best to leave the replacing of the fan clutch up to a professional mechanic, unless of course you know what you are doing. But if you are finding that the vehicle is fine on the highway, yet when you are in traffic or you are stuck at a red light and the heat gauge immediately goes up and gets too hot, then it may be time for you to get it replaced.

It is quite a simply process as the fan clutch is simply sandwiched between the can and the connecting shaft. All that would have to be done is to unbolt the fan and remove the clutch. The new one is then installed and the fan re-attached and you will then be on your way. It is advisable to may be do a coolant flush and put in a new thermostat at the same time.

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[shogun]

and another write-up by MWrench, the ultimate fan clutch test
http://www.mwrench.com/Whitepapers/FanClutchtest.pdf

[e34.535i.sport]

The big 32mm(?) fan nut has left handed thread so you need to get a big spanner on it and hit the end with a hammer clockwise to undo it (as you normally would to tighten it)... It needs a quick knock at first otherwise you'll be lucky to undo it. Once it's off you can swap the clutch and keep the fan blades. Not sure if u'll be able to swap the four hole for the three... I'd have a look at the fan blades first to see before you start!

[e34.535i.sport]

It is quite a simply process as the fan clutch is simply sandwiched between the can and the connecting shaft. All that would have to be done is to unbolt the fan and remove the clutch. The new one is then installed and the fan re-attached and you will then be on your way. It is advisable to may be do a coolant flush and put in a new thermostat at the same time.

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+1

I wrote this shortly after renewing some of my stuff up front...

http://www.bimmernut.com/forum/showt...stat+waterpump

[Rus]

The big 32mm(?) fan nut has left handed thread so you need to get a big spanner on it and hit the end with a hammer clockwise to undo it (as you normally would to tighten it)...

Please don't tell me that you give that wrench a smack with a hammer to tighten the fan clutch nut. Its your car and your choice, but personally I don't even use a wrench on that nut when installing the fan. Get it threaded on most of the way and then give the fan a hearty spin. That's it...done. It will not come off (threaded against the rotation of the engine) and removal takes all of 15 seconds with a light tap on the wrench with my hand. I've learned the hard way that tightening the fan nut (like a mechanic did before me) is a recipe for lots of frustration later. Just my $.02

[e34.535i.sport]

Please don't tell me that you give that wrench a smack with a hammer to tighten the fan clutch nut. Its your car and your choice, but personally I don't even use a wrench on that nut when installing the fan. Get it threaded on most of the way and then give the fan a hearty spin. That's it...done. It will not come off (threaded against the rotation of the engine) and removal takes all of 15 seconds with a light tap on the wrench with my hand. I've learned the hard way that tightening the fan nut (like a mechanic did before me) is a recipe for lots of frustration later. Just my $.02

Sorry Rus I think you misunderstand me... When I said "as you normally would to tighten it" I meant the direction clockwise not the method of tightening!

[shogun]

gentle fan persuader removal tool
http://www.bimmerboard.com/forums/posts/631988

[Rus]

Sorry Rus I think you misunderstand me... When I said "as you normally would to tighten it" I meant the direction clockwise not the method of tightening!

Oops Sorry about that. When I misread that, nightmarish memories from my past surfaced. :-p