Fan Clutch Replacement

I’m going to point-form this rather than add a whole lot of narration that no one really cares about. Basically, since I replaced the thermostat the second time the car has been running hot, especially at idle. This is probably caused by one of three things:

1 – Coolant circulation problem:


  1. Radiator is clogged – doubtful, rad is only 2 months old
  2. Water pump is broken – doubtful, water pump is only 2 months old
  3. Air is in the system – doubtful, new thermostat has a hole in it and bleeding the system produced no air bubbles just coolant
  4. Coolant is low, coolant system is losing pressure – checked frequently, level holds steady. A pressure issue is unlikely without a leak.

2 – Air circulation problem:


  1. Mechanical fan is not working
  2. Auxiliary (electric) fan is not working

3 – Ignition or Valve Timing problem:


  1. Let’s not even go there… drive belt is 2 months old and car was professionally tuned.

My attention turned to the second set of possible causes for the overheating since it’s easy to test the air circulation system. From what I’ve read and been told, the mechanical fan should run all the time but run faster as coolant gets hotter and engages the fan’s clutch. At 80C the thermostat opens and allows coolant into the engine. If the coolant gets really hot the aux (electrical) fan will engage low speed mode at 91C, then go into high speed mode if the temperature continues to climb to 99C. That shouldn’t even happen because the mechanical fan should be sufficient to cool the rad and keep coolant below 91C. The mechanical fan would require parts but the electrical fan might be easier to fix so I checked that first:

GOOD: aux fan comes on when A/C is on, at least it runs as listed in the Bentley manual I jumpered the thermostat switch and found:

  • GOOD: fan high-speed works
  • BAD: fan low-speed did not work. Possible causes:
    1. could be the resistor, which comes in two variants and is very difficult to replace without removing the radiator
    2. fan relay is blown
  • GOOD: Replaced relay K1 and low and behold now both low and high speed modes are working when jumpered

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  • BAD: visually, the fan was turning a speed I would describe as “slow” even when hot
  • VERY BAD: at operating temperature I was able to stop the fan blade using a single piece of cardboard (a rolled up newspaper could have been used too)
  • GOOD: belt seems tight when depressed with my finger, less than 1/4 of deviation
  • BAD: both upper and lower hoses coming from rad were hot (only indicates a problem, not necessarily a clogged radiator)

I checked with my friend and mechanic (who will remain nameless so he will not be inundated with after hours petitions like mine) for guidance. He didn’t offer any alternative theories so I decided to go ahead with the fan clutch replacement. He hooked me up with a new fan clutch and most importantly a 32mm fan clutch wrench (which is long and thin) and a pulley retainer. If you ever do this job I cannot overstate the value of having the right tools especially the pulley retainer not sure of the quality but you can buy both from Amazon for under $30.00. You can use a regular 32mm wrench but there will not be room for a pulley retainer as well, therefore the special thin versions are required. Here’s how this went down:

  • removed the old fan using the 32mm wrench by loosening the reverse threaded nut (when standing in front of the car righty loosey lefty tighty, or clockwise to loosen)
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  • didn’t need the pulley retainer here because the belts were nicely tensioned
  • didn’t need to whack the wrench with a hammer, nut loosened easily probably because it hadn’t been on for long
  • turned the fan mostly by hand until the last couple turns where the wrench was
  • used the wrench and my spare hand to grab the fan but still almost dropped it
  • there is only millimetres of extra space between the rad and the fan once it’s removed
  • tried to remove the fan blade from the fan clutch
  • my fan had regular bolts, not M6 (hex) bolts so there was little room for a socket between the bolt and the clutch
  • fan kept wanting to spin out of my grip while trying to loosen the bolts
  • vice grips couldn’t get good purchase anywhere
  • breaker bar didn’t help, just aggravated the problem
  • posted on facebook e30 group looking for either:
    • A) a bench mounted vice to use
    • B) a replacement fan
  • thankfully someone (thanks, Vivek) was able to provide both but I had to remove the fan from a clutch myself and also the vice was not on a bench
  • went to get fan
  • needed pulley retainer in order to remove fan from donor vehicle
  • noticed this fan had M6 bolts, was able to remove all of them by using my socket wrench and leveraging my grip against the edge of the fan directly across from the bolt I was removing
  • did the same trick on 2 of the bolts on my fan
  • used the vice clamped onto 2 screwdrivers stuck through the tines on the clutch to hold it in place and remove the last 2 bolts
  • amazingly, the clutch will not come apart from the fan blade! no explanation for this. locktite?
  • thankfully I had the fan blade from the donor vehicle
  • paid vivek $5 for the fan blade
  • went home, cleaned the fan and attached it to the new clutch (torqued M6 bolts to 80 +/-5 in. lbs.)
  • carefully threaded new clutch onto water pump bolt by hand until the pulley and belt started moving
  • used the pulley retainer again to finish the job and tighten the bolt with the wrench (guessed at how tight it should be… it’s reverse threaded so it shouldn’t fall off)

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Mina really wanted to go for a drive in so we all piled in, got coffee and gas, went to Campbell, then back home, then to Los Gatos to drop off the tools at my friend’s place and back home again. When we were getting coffee I noticed this couple standing next to a BMW X3 who were smiling and nodding at me. His name was Will and he just wanted to say how great it was to see someone in an e30 with the whole family. It was cool to chat even for a couple minutes and it turns out he’s in the BMW Club so maybe I’ll see him again. Car was either running a little cool in traffic or just a tick warm at idle, but totally within allowable ranges. E30s are known for having jumpy, analog dials so this is fine. I’m really happy that my car is running properly again as I’ve been limiting myself to short trips and eyeing the temperature gauge nervously all week so I am glad that I can go for long morning drives again.

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Addendum I:

What caused all this? I think the fan clutch probably didn’t like being jostled so violently when I was hammering away on the thermostat two weeks ago. That’s the only explaination I have for it’s sudden failure.

Addendum II:

Got the clutch off the fan blade. Hit it a few times with the hammer. Now I have a spare.

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August 19, 2012 mechanical, repairs