shogun
04-23-2013, 10:38 PM
First, lets discuss what the fan clutch does and why it is there. The fan clutch is just what the name says, it is a mechanism that will clutch the fan on and off depending on the need for more or less cooling air to flow thru the radiator. It is a thermostatically controlled device that when operating normally will vary the fan speed independently of the engine speed. When cruising down the road at freeway speeds, with outside temperature less then desert conditions, the fan should be merely be idling along, turning just fast enough to add a little air flow when needed, in this way the fan noise and drag on the engine is greatly reduced. When reducing speed, the fan clutch will sense higher temperatures thru the radiator and “clutch up” thereby increasing the fan speed to help maintain constant engine temperature. It may in fact, cycle as the temperature of the air thru the radiator changes depending on airflow. If the fan clutch operation is normal, when first starting the car, the fan clutch should “clutch up” and an increase in noise and airflow should be obvious. After about 60-90 seconds, the fan will un-clutch and the noise and airflow will drop. The fan will continue to turn but at a much reduced speed. As the engine warms and the thermostat opens to regulate the temperature, the air thru the radiator gets hotter and the clutch will sense this, thereby increasing the speed of the fan to maintain a normal operating temperature.
First signs of trouble:
A normal temperature indication at freeway speeds and an increasing temperature as the vehicle slows is one of the first indications of trouble. Many other things may give this indication but if the temperature seems to be stable at speeds but climbs in traffic or while stopped, this is a good indication that the fan clutch isn’t working correctly. As the temperature continues to climb, the auxiliary electric fan should start but may not provide enough air to keep the engine from overheating.
Another sign of trouble is if the fan noise is high and never decreases after starting, and is there anytime the engine RPM is higher then idle, this means that the fan clutch is “frozen” and is not releasing. Although this will not result in immediately serious trouble, it will load the engine continually and gas MPG will be reduced. Load on the fan belt(s) will be higher and shorten the life of that component also.
Testing the fan clutch:
If you have reason to suspect that the fan clutch is defective, here is the recommended procedure to verify the condition of the fan clutch.
1. Start the car (cold) with the hood open and note if the fan is turning, increase the engine RPM and note if the fan turns faster and the noise increases, if it does, first good indication, if it does not increase speed/noise, clutch is bad and needs to be replaced. (Remember, this must be tested after the car has been off for and extended period, over night etc.)
2. Leave engine running and note if the fan starts to slow down after 2-5 minutes, speed/noise should diminish and even raising the RPM, the fan should not make as much noise as when first starting, if it does slow, this is the second good indication. If speed/noise does not decrease, clutch may be “frozen” and should be replaced.
3. Leave the engine idle and watch the temperature indicator. When normal operating temperature has been reached, some increase in fan speed/noise should be noted, in particular when the RPM is increased. If temperature is fairly stable and the fan noise/speed increases or cycles, third good indication. If temperature indication continues to increase, with no increase in fan noise/speed, clutch is defective and should be replaced.
4. After the engine is at normal operating temperature or above, is the only time that the “rolled up newspaper” test that many people talk about should be performed! Take some newspaper and roll it up into a long narrow tube. Be carefull, keep hands and fingers away from the fan while performing this test! With the engine at full operating temperature and idling, take the rolled up paper and insert it on the back side of the fan and try to reach the hub of the fan avoiding the blades until close to the hub. Push the rolled paper at the fan increasing the friction to the hub area of the fan. If the fan can not be stopped easily this is the fourth good indication, if it can be stopped the clutch is defective and should be replaced. Again, this test can only be performed when the engine is at or above full operating temperature.
Testing can be performed in any order but just make sure the conditions during testing are those that are specified for that specific test.
Do not continue to operate the engine if the temperature continues to rise and certainly stop if the temperature approaches “redline”.
Once written by MWrench
Attached find a techncail description of the fan clutch
Fan clutches: Function and handling, storage, starting noise
Important Service Bulletin Fan clutches: Function and handling - Hints for experts (from an online Sachs info I once found years ago)
Overview
The SACHS fan clutch assists the engine to maintain its correct operating temperature. When the engine temperature exceeds a certain level, the fan clutch is activated causing additional air flow through the radiator. The fan clutch is activated when hot air passes over a bi-metal strip 1 on the fan clutch, causing deformation of the bi-metal strip which activates the control pin 2.
The control pin opens the valve 3 allowing silicone oil 4 to enter the drive chamber of the fan clutch. The temperature controls the speed of the fan clutch i. e. higher temperature causes higher speed. As temperature decreases, so does the speed of the fan clutch.
Transport and Storage
To ensure proper function of the fan clutch we recommend that these instructions be followed. It is most important that the fan clutch be positioned correctly during transportation and storage. Please note the arrow on the fan clutch package. The fan clutch should be stored either vertically but preferably flat with the arrow pointing up. This is to ensure that silicone oil does not leak past the control pin seal. Should a small amount of oil leak past the control pin seal due to incorrect storage, the fan clutch will still perform correctly.
Attention:
Fan clutches must be stored flat in the box with the arrow pointing up.
Warning: Please note that the bi-metal strip on the front of the clutch has been calibrated to perform at a particular temperature range. Changing the position of this strip will change the performance of the fan clutch.
Avoid injury – keep clear of fan and pulleys when engine is running.
Service information
Fan clutches are often replaced even though they are performing correctly. In order to diagnose a cooling system problem, it is recommended that the following be checked:
Check the coolant level.
Check the temperature gauge.
Check that radiator fins are free from dirt and insects.
Check the proper operation of the thermostat.
Check the fan belt.
Check the operation of the water pump.
Check if sufficient hot air can flow through the radiator to activate the fan clutch.
Check for blockages inside the radiator preventing flow of coolant.
Check that the fan is the correct type and undamaged.
Noise generated by the AC clutch or by the engine should be investigated.
Fitting Instructions:
Adjust water pump drive belt to specification (do not overtighten).
Unscrew fan clutch from spindle 6.
Caution Mercedes Benz applications. Check the direction of rotation of the fan. The direction of rotation is also shown on the mounting flange. The engine side of the fan clutch required to be mounted to the spindle is marked accordingly. Radiator fins are of solid material 7.
1) An anti clockwise (left hand) rotating clutch has a right hand threaded nut.
2) A clockwise (right hand) rotating clutch has a left hand threaded nut.
Note: To ensure that the correct part number is fitted for the vehicle application see application list. All bolts should be tightened to recommended torque (MB 10 Nm / BMW 12 Nm). (Mercedes Benz mark „Vorne Front“ in the direction of travel). Tighten the fan clutch onto spindle with the specified torque (DB 45 Nm / BMW 40+10 Nm).
And from an old T*S (maybe 10 years old)
SI Viscous Fan clutches storage/noise cold/tightening
All models storage information
It is no longer neccesary to store viscous fan clutches upright or on an angle. This change is due to the installation of improved seals in the fan clutch assembly.
Noise during cold starts
Due to the basic design of the fan clutch, fan noise may occur for up to 60 seconds after starting the engine in cool weather. This is because the fluid in the viscous fan coupling (which has entered the working chamber of the fan clutch) must be returned to the supply chamber by the pumping action of the clutch. Depending on the ambient temperature, this pumping action could take up to 60 seconds, after which the fan begins to freewheel.
Tightening torque
Tightening torque for the viscous fan clutch of all engines is 40 + 10 Nm (29 +7 ft. lbs.). However, when using special tool 88 88 6 115 040 the torque wrench must be set to 30 Nm/22 ft. lbs.
First signs of trouble:
A normal temperature indication at freeway speeds and an increasing temperature as the vehicle slows is one of the first indications of trouble. Many other things may give this indication but if the temperature seems to be stable at speeds but climbs in traffic or while stopped, this is a good indication that the fan clutch isn’t working correctly. As the temperature continues to climb, the auxiliary electric fan should start but may not provide enough air to keep the engine from overheating.
Another sign of trouble is if the fan noise is high and never decreases after starting, and is there anytime the engine RPM is higher then idle, this means that the fan clutch is “frozen” and is not releasing. Although this will not result in immediately serious trouble, it will load the engine continually and gas MPG will be reduced. Load on the fan belt(s) will be higher and shorten the life of that component also.
Testing the fan clutch:
If you have reason to suspect that the fan clutch is defective, here is the recommended procedure to verify the condition of the fan clutch.
1. Start the car (cold) with the hood open and note if the fan is turning, increase the engine RPM and note if the fan turns faster and the noise increases, if it does, first good indication, if it does not increase speed/noise, clutch is bad and needs to be replaced. (Remember, this must be tested after the car has been off for and extended period, over night etc.)
2. Leave engine running and note if the fan starts to slow down after 2-5 minutes, speed/noise should diminish and even raising the RPM, the fan should not make as much noise as when first starting, if it does slow, this is the second good indication. If speed/noise does not decrease, clutch may be “frozen” and should be replaced.
3. Leave the engine idle and watch the temperature indicator. When normal operating temperature has been reached, some increase in fan speed/noise should be noted, in particular when the RPM is increased. If temperature is fairly stable and the fan noise/speed increases or cycles, third good indication. If temperature indication continues to increase, with no increase in fan noise/speed, clutch is defective and should be replaced.
4. After the engine is at normal operating temperature or above, is the only time that the “rolled up newspaper” test that many people talk about should be performed! Take some newspaper and roll it up into a long narrow tube. Be carefull, keep hands and fingers away from the fan while performing this test! With the engine at full operating temperature and idling, take the rolled up paper and insert it on the back side of the fan and try to reach the hub of the fan avoiding the blades until close to the hub. Push the rolled paper at the fan increasing the friction to the hub area of the fan. If the fan can not be stopped easily this is the fourth good indication, if it can be stopped the clutch is defective and should be replaced. Again, this test can only be performed when the engine is at or above full operating temperature.
Testing can be performed in any order but just make sure the conditions during testing are those that are specified for that specific test.
Do not continue to operate the engine if the temperature continues to rise and certainly stop if the temperature approaches “redline”.
Once written by MWrench
Attached find a techncail description of the fan clutch
Fan clutches: Function and handling, storage, starting noise
Important Service Bulletin Fan clutches: Function and handling - Hints for experts (from an online Sachs info I once found years ago)
Overview
The SACHS fan clutch assists the engine to maintain its correct operating temperature. When the engine temperature exceeds a certain level, the fan clutch is activated causing additional air flow through the radiator. The fan clutch is activated when hot air passes over a bi-metal strip 1 on the fan clutch, causing deformation of the bi-metal strip which activates the control pin 2.
The control pin opens the valve 3 allowing silicone oil 4 to enter the drive chamber of the fan clutch. The temperature controls the speed of the fan clutch i. e. higher temperature causes higher speed. As temperature decreases, so does the speed of the fan clutch.
Transport and Storage
To ensure proper function of the fan clutch we recommend that these instructions be followed. It is most important that the fan clutch be positioned correctly during transportation and storage. Please note the arrow on the fan clutch package. The fan clutch should be stored either vertically but preferably flat with the arrow pointing up. This is to ensure that silicone oil does not leak past the control pin seal. Should a small amount of oil leak past the control pin seal due to incorrect storage, the fan clutch will still perform correctly.
Attention:
Fan clutches must be stored flat in the box with the arrow pointing up.
Warning: Please note that the bi-metal strip on the front of the clutch has been calibrated to perform at a particular temperature range. Changing the position of this strip will change the performance of the fan clutch.
Avoid injury – keep clear of fan and pulleys when engine is running.
Service information
Fan clutches are often replaced even though they are performing correctly. In order to diagnose a cooling system problem, it is recommended that the following be checked:
Check the coolant level.
Check the temperature gauge.
Check that radiator fins are free from dirt and insects.
Check the proper operation of the thermostat.
Check the fan belt.
Check the operation of the water pump.
Check if sufficient hot air can flow through the radiator to activate the fan clutch.
Check for blockages inside the radiator preventing flow of coolant.
Check that the fan is the correct type and undamaged.
Noise generated by the AC clutch or by the engine should be investigated.
Fitting Instructions:
Adjust water pump drive belt to specification (do not overtighten).
Unscrew fan clutch from spindle 6.
Caution Mercedes Benz applications. Check the direction of rotation of the fan. The direction of rotation is also shown on the mounting flange. The engine side of the fan clutch required to be mounted to the spindle is marked accordingly. Radiator fins are of solid material 7.
1) An anti clockwise (left hand) rotating clutch has a right hand threaded nut.
2) A clockwise (right hand) rotating clutch has a left hand threaded nut.
Note: To ensure that the correct part number is fitted for the vehicle application see application list. All bolts should be tightened to recommended torque (MB 10 Nm / BMW 12 Nm). (Mercedes Benz mark „Vorne Front“ in the direction of travel). Tighten the fan clutch onto spindle with the specified torque (DB 45 Nm / BMW 40+10 Nm).
And from an old T*S (maybe 10 years old)
SI Viscous Fan clutches storage/noise cold/tightening
All models storage information
It is no longer neccesary to store viscous fan clutches upright or on an angle. This change is due to the installation of improved seals in the fan clutch assembly.
Noise during cold starts
Due to the basic design of the fan clutch, fan noise may occur for up to 60 seconds after starting the engine in cool weather. This is because the fluid in the viscous fan coupling (which has entered the working chamber of the fan clutch) must be returned to the supply chamber by the pumping action of the clutch. Depending on the ambient temperature, this pumping action could take up to 60 seconds, after which the fan begins to freewheel.
Tightening torque
Tightening torque for the viscous fan clutch of all engines is 40 + 10 Nm (29 +7 ft. lbs.). However, when using special tool 88 88 6 115 040 the torque wrench must be set to 30 Nm/22 ft. lbs.