Brief history and possible triumph of my cooling system! (was "Check a fan clutch?") I keep finding conflicting information on this... How can a verify that a thermal fan clutch is working correctly? My understanding of how these work is something like this: It's freewheeling, or nearly freewheeling, until it reaches a certain temp and then it starts to grip. It lets go when the temp comes back down. Shouldn't I be able to go for a drive, warm it up, then shut it off and turn the fan by hand and feel resistance? Is it gradual or is it kind of an on/off type deal? How hot should it be before it grips?
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 [FONT=NJLAIL+TimesNewRoman,Bold,Times New Roman][FONT=NJLAIL+TimesNewRoman,Bold,Times New Roman]does not increase [/FONT][/FONT]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 [FONT=NJLAIL+TimesNewRoman,Bold,Times New Roman][FONT=NJLAIL+TimesNewRoman,Bold,Times New Roman]does not decrease[/FONT][/FONT], 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 [FONT=NJLAIL+TimesNewRoman,Bold,Times New Roman][FONT=NJLAIL+TimesNewRoman,Bold,Times New Roman]no increase [/FONT][/FONT]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. [FONT=NJLAIL+TimesNewRoman,Bold,Times New Roman][FONT=NJLAIL+TimesNewRoman,Bold,Times New Roman]Be carefull, keep hands and fingers away from the fan while performing this test! [/FONT][/FONT]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 [FONT=NJLAIL+TimesNewRoman,Bold,Times New Roman][FONT=NJLAIL+TimesNewRoman,Bold,Times New Roman]can be stopped [/FONT][/FONT]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.
Just an update here. Haven't installed a new fan clutch yet, but have determined that I need one. Thanks shaneb. So I never actually explained what I did or why... I have a .060" over 351w and I drive this thing around Memphis. Being prone to surprise (and non-surprise) bouts of inescapable traffic jams, and given its latitude, Memphis is a fantastic place to test the limits of one's cooling system during the summer months. Basically with this car's equipment and duties, it needs the ultimate cooling system, and I may have found it! We'll know after this weekend. I had an electric fan and shroud from a late Escort with a thermostatic controller that worked pretty well for my 302, (basically the same as the beloved Taurus fan but with a more compact shroud) Then I installed AC and later I crammed this bigassed engine in there, and that fan became insufficient to say the least when the weather gets hot. I have a big aluminum radiator so that was never the problem; got to be airflow. So I yanked the electric fan and installed an 18" aluminum flex fan. That was a joke, especially without a shroud, but it did have one positive result: I learned that my powerful and nicely compact Escort fan/shroud assembly was restrictive when the car is moving. Temps still shot up quick when idling on the hot asphalt with the AC on, but they also shot down when I got up some speed, and much more quickly than before. I decided what I needed was a less restrictive fan shroud and a fan that would move more air than this flex thing did. Enter the Junkyard. I brought a radiator with me that's identical to the one I currently have installed, (except for the hole I managed to put in it ) so I could look for a shroud that would fit it well. Also was looking for the biggest, meanest clutch fan I could find. Didn't take me long to see that a shroud from an early 90's V6 Explorer would be a perfect fit for the radiator, but the fan was no good due to it being reverse rotation. (And Explorer fans are junk. Have you ever seen one that's not cracked?) But the fan I did find is awesome. 19" 7-blade monstrosity from a '75 Thunderbird with a 460! If this doesn't keep it cool, something is wrong. I put it all together and it worked so much better. But to my disbelief, the temp slowly climbs up when I'm stopped, eventually nipping at the heels of 230 degrees before I have to fire up the heater. I decided the clutch had to be bad, and I'm pretty sure it is, so I'll be replacing that. Found out something else last night though - when it gets hot and I'm stuck, I can rev the engine just a little above idle and it comes right back down again, so I have one more thing I want to try. Smaller water pump pulley. My current one is just about as big as my crank pulley, but if I can spin both the pump and the fan just a little bit faster by using a smaller one, along with having a clutch that works right, I may finally have achieved cooling nirvana. Best part is each little improvement I've made to airflow is making my AC that much colder too...
**DISCLAIMER The above post was written on 28 hours' sleep deprivation and 15mg of Adderall. If at first it doesn't make sense to you, read it faster.
Testing The Fan Clutch: 1. Start car and bring to operating temperature. 2. With one hand rev engine to 5000 rpm. 3. Stick fingers of second hand into rotational path of fan. 4. If the fingers of your second hand fall to the ground the clutch is working as designed. 5. Enter car, proceed to nearest emergency room.
I don't know if your car is automatic or not, but my friends will run hot sitting in traffic. He pops his in neutral to sit out long lights and it really helps keep the temp down! I'm not sure how this would help because it only lets the engine idle up a little more, but it really works!
Well I think it's twofold... One, the engine isn't under any load anymore, so maybe a bit less heat is being generated, and two, the fan and water pump are spinning just a bit faster. I'm thinking "just a bit" is really all it's going to take, so that's why I think a smaller water pump pulley is going to help me.
Sometimes smaller IS better .. The hunt is on for a smaller one.. smaller pulley. I hate having to do these kinda searches.. So time consuming. Keep us posted. I'd like to know if the theory works, which I think it should. Works on alternators..
Three days driving with the smaller pulley and new fan clutch. AC is blowing gloriously cold, engine temp has yet to go over 205. (195* thermostat)
