fan clutch-- maybe going bad ?

[fairchild]

Checking the fan clutch. A little stiff when cold. Less stiff when full temp. When fully warmed up -- I can flip a blade
as hard as I can it it will rotate about 1/4 turn. Seems stiffer cold than hot. Is it just starting to go ?

(just changed WP and thermostat--- after 20 min at idle- temp gauge it as 12-oclock-- perfectly centered on the little thermometer
graphic in gauge. Takes 7 minutes from cold to that 50% point)

Should I replace Fan clutch ? (no way to know how old it might be-) Im guessing - YES- but I just want some backup here
Running really smooth except a little idle hiccup during 1-st minute of startup (bad vanos O-rings?)

Tim

[shogun]

Fan clutch test http://www.mwrench.com/Whitepapers/FanClutchtest.pdf
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”.

[Mr Bingley]

Regardless of whether it's good or bad, many of us delete it in favor of an electric fan. The clutch fans have a tendency to blow up at the worst moments and can cause serious damage.

[rf900rkw]

That test procedure is bogus. Some because of how our cars work, but mostly because it ignores how clutch fans work.


On a Z3 there is only one proper test for the fan clutch. Remove it and lock it in the barn on the highest shelf. If it crawls back to the car and reinstalled itself, it's good.

[rf900rkw]

In all seriousness, the fan clutch can not make a Z3 overheat. The factory electric fan is more than enough to keep things cool. The one thing you need here is to ignore the temp gauge. Dead center just means the engine is somewhere in a very wide band that BMW defined as normal. 75C-105C. The thermostat doesn't open until the mid 90's on your car, so you can have the gauge dead center and the radiator still stone cold. You need to use an OBDii scanner to get a reasonable realtime temp reading. And even that won't tell the story you think it is, since your ECT is on the engine inlet side.

I've said this to the point of maddness, but since you are new here... "the fan does not cool the engine". the fan cools the radiator. The radiator cools the engine. The thermostat works on the inlet side of the engine. It draws cooled coolant from the radiator as needed. When the supply of cooled coolant is exhausted, the switch on the cold side tank turns the fam on, which blows on the radiator and cools off another batch. The clutch fan works the same way, just much more slowly. It doesn't react to the temp of the radiator exit coolant. It reacts to the heat in the airstream radiated by the hot exit coolant. It does not watch the dash gauge. Indeed it does not monitor the engine temp at all. It reacts to the temp of the air exiting the radiator core. As the air warms, the fan thermo warms and the fan starts engaging. This is why any clutch fan test that relies on anything but the air stream temp is bogus. And every test I've ever seen relies on the dash gauge and a stick of newspaper.

[fairchild]

Sounds like I should test the temp switch on the cold side. I have not yet seen the electric fan operate from engine heat. It does come on when
I activate the AC compressor clutch. Now that I remember - I think I saw an oval snout on the side of the radiator with nothing plugged into it.
Perhaps that is the temp switch ? Tomorrow I will hunt for a loose dangling electrical wire and plug----

Thanks for the heads -up ----- I am on the steep learning curve called BMW.

Incidentally- I let it idle for about 20 min- went for a 15 min. drive around the property--- came back into shop-- more idle-- I could stop fan with 1 finger.
But if its not hot enough to trigger the goo in the clutch---

what would happen if the fan ran all the time? like if I made a fan clutch delete device. Its 100 degrees here in the summer time for most of the summer.
Seems like if the rad water was cooler the thermostat would just find a more colosed equilibrium point. (?) ( I hate fan clutches---- like old school fan which
was "one" with the shaft ! )

Tim

[LannVouivre]

On a Z3 there is only one proper test for the fan clutch. Remove it and lock it in the barn on the highest shelf. If it crawls back to the car and reinstalled itself, it's good.

If it crawls back and reinstalls itself, get an exorcism performed because removing the clutch fan is a PITA and this can only be the work of the devil trying to make you miserable. The clutch fan is only really useful if your electric fan can't operate. Speaking of which, the temperature switch can have incorrect wiring, right?

[rf900rkw]

Having a fan locked to the waterpump worked "okay" when engine redlines were below 4000. On our 7K engines, it would explode. That is the whole point of the fan delete. The fan clutch *will* evenually seize, at least partially, and cause the plastic fan to explode. Radiators, mucho plastic, and the hood are destroyed as a result.

[Allan Parsons]

I also live in Orlando and my "fan and clutch" have been removed for 3 years now. Never overheats and the "elec fan" only kicks in when the A/C is on

[Tom Liberatore]

You've convinced me, but not having a barn, I had to store it nearby, luckily it didn't try to reinstall itself before I could get the hood closed!