Faculty of Industrial Technology, Lampang Rajabhat University, THAILAND

How to Replace Fan Clutch of BMW E34 M50.

l by Assoc.Prof. BOONCHAT NETISAK Language : ภาษาไทย ll ENGLISH l l MAIN MENU l

Introduction to FAN CLUTCH

    Fan clutch of radiator cooling fan on your BMW e34 car is located in front of the engine behind the radiator. It looks like an aluminum UFO with fins around it's body. The clutch is at the center of the fan assmbly and is engine driven via a poly-ribbed belt. The fan clutch contains hydraulic oil which its viscosity varies upon the temperature of air flowing from the radiator. the hotter the air, and oil, the faster the fan runs. So fan will always run at an appropriate speed with engine coolant temperature, thus keeping your engine in good health.

    When your car is aged, say, over 10 years old, the fan clutch would be old too and you cannot expect it to work as a new one because the hydraulic oil might have leaked or spilled out. It may run at constant low speed (sometimes at high speed) at all temperature which can cause your engine to run at high temperature. (or over cooling by high speed fan).

  • This photo is an old fan clutch.
  • It has aluminum fins for heat sensing from flow air with three holes to locate the fan blade.
  • The nut at the center can turns with resistance from hydraulic viscosity in the clutch assembly.

  • This fan clutch was produced on 27/06/1995.
  • It's been in use for over 10 years. It's old and does not work efficiently as it was.
  • It runs like a lazy fan all the time, hot or cool .


      While engine run : We should observe as follow.
    • The fan only runs at low speed or at high speed , whether in hot or cool engine temperature, it runs at the same speed.
    • Engine temperature gauge rises up, showing high over half scale, while cooling system is normal.
    • Air-condition system can't produce adequate cool air , while air-condition system is normal.

      While turn off engine and cold : We should observe as follow.
    • You can notice the dirty oozy of spilled hydraulic oil mixed with dust on the fan clutch body.
    • Spin the fan by hand it should spin with slight resistant of hydraulic oil.
      If the fan freewheels with little resistance or cannot turned by hand and there are signs of oil leakage, the clutch should be replaced.

      When the fan clutch is not good, we offer two ways for your consideration as following.

    • Replace bad fan clutch with the new one, very surely and not difficult to do but more little expensive.
    • Rebuild the old fan clutch by drill a hole on the fan clutch body and refill hydraulic oil inside and firmly close that hole when finish. This method I never did before, but heard from some one that it has good result and low cost, if you have interest you can search in anoter website.

      This page I will state only how to replace.

      Prepare the spare part.

    • One piece of the new fan clutch or rebuilt fan clutch.
    • Please inspect size, center nut and three holes to locate the fan blade as same as the old fan clutch.
    • You can read the specification and another detail indicated on the fan clutch pagage.
    • Check date / month / year of production, select newly product.

      Prepare the tools.

      1. Allen wrench, hex size 5 m.m.
      2. Flat-blade screw driver.
      3. Open-end wrench 32 m.m.
      4. Pulley locking tool. (special tool made by ourself)
  • We can make 32 m.m. open-end wrench by ourself with iron plate 2 - 2.5 m.m. thick , 40 c.m. long.
  • How to use this wrench loossen / tighten on central nut of fan clutch.
  • We can make Pulley locking tool. (special tool) by ourself with iron plate 2 - 2.5 m.m. thick , width 2.5 c.m. and 40 c.m. long.
  • Bore an oval hole 1x1.5 c.m. near the end for locking on bolt head of fan pulley.
  • How to use this special tool we made locking on bolt head of fan pulley.
    (This picture to demo how to lock the pulley with special tool)
    • CAUTION.
      1. Stop the engine and let it cool is more comfort and safety to working.
      2. Pull out starting key and keep in safety place or remove ground line of battery.
      Danger.. if the engine being start while working.

    Steps to Replace Fan Clutch.

  • There are two plastic rivets locked at top corner of fan shroud.
  • Pry out two plastic rivets locked on top of fan shroud with screw driver.
  • Gently remove the fan shroud out.
  • Notice the big nut 32 m.m. at the center of engine pulley.
  • Fix engine pulley with our special pulley locking tool.
  • Turn 32 m.m. center nut with open-end wrench clockwise.
  • Loosen center nut , turn fan blade clockwise slowly, when out off thread, pick out it carefully and lay down on plane ground.
  • Remove the fan blade from the clutch by thread off 3 bolts with allen wrench hex 5 m.m.
  • Install new clutch at center of fan blade, tighten three hex screws.
  • Clean and incpect poly-ribbed drive belt components.
  • Install the fan (with new clutch) back to engine pulley.
  • Turn center nut anti-clockwise to engine pulley with high concentration.
    (Use 32 m.m. open-end wrench and our special pulley locking tool for little tighten.)
  • Install the fan shroud and plastic rivets lock.
  • Spinning the fan blade by hand (engine off), it does not touch eny parts around.
  • Start the engine, inspect fan turning.
  • Finish Our DIY.
    If replace with new clutch , we shall be replace next time more 8 years.

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