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It's been hot for a week or more (over 90F). The temp gauge has been steady at 9 o'clock. Went up a bit but not beyond 10 o'clock yesterday while in slow traffic at around 95F. Got home, turned off engine, popped hood, turned rad fan and found it spun easily.
Is the fan clutch defective or do they activate at higher temps?
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1980 245 Canadian B21A with SU carb and M46 trans in Brampton, Ont.
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Does you fan roar when you first start the car, then die down? The fluids settle somehow and if it has been sitting, couple. The turning fan distributes the fluid so the fan then freewheels if it is not hot enough. If your fan roars at start up, at least you know you have fluid for the coupling.
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Paul NW Indiana '89 740 Turbo 110,000
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Trev,
Check this out: http://mpvi.net/ie/ie0029.htm
• While the fan clutch detects a temperature lower than 80°C, it remains OFF and the fan revolution speed is constant (1,200 r/min.(rpm)) regardless of the engine speed.
• As the temperature reaches 80°C to 95°C, the fan clutch turns ON gradually and the fan revolution speed increases.
• A temperature exceeding 95°C causes the fan clutch to turn ON and the fan revolution speed to increase in proportion with the engine speed.
• Once the engine speed exceeds a specified one, however, the fan revolution speed becomes constant (3,600 r/min.(rpm)).
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Trev,
Check this out: http://mpvi.net/ie/ie0029.htm
• While the fan clutch detects a temperature lower than 80°C, it remains OFF and the fan revolution speed is constant (1,200 r/min.(rpm)) regardless of the engine speed.
• As the temperature reaches 80°C to 95°C, the fan clutch turns ON gradually and the fan revolution speed increases.
• A temperature exceeding 95°C causes the fan clutch to turn ON and the fan revolution speed to increase in proportion with the engine speed.
• Once the engine speed exceeds a specified one, however, the fan revolution speed becomes constant (3,600 r/min.(rpm)).
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Hmm. So, basically, since I don't have A/C or any hills to climb, I'll have to assume the fan clutch is okay. (I guess I could pray for some really hot days, but I've got better things to do with my prayers.)
Thanks. (Saved that web page just in case I get the urge to open the clutch up and tinker.)
--
1980 245 Canadian B21A with SU carb and M46 trans in Brampton, Ont.
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Those are ºs Centigrade (referencing the analysis of fan clutch operation posted previously). Radiator fluid exit temps will easily get to 95ºC and beyond with a non-functioning fan. Details below.
From my testing of radiator coolant exit temps - part of getting my electric radiator fan conversion working in my '89 245 - I can tell you that 80ºC is a typical OK temp for water coming out of the rad, and 92º is definitely too hot.
Testing of the mechanical fan w/clutch yesterday showed that I could not get the rad exit water up to 85ºC no matter how I drove or idled the car - including accelerating up highway hills. I currently have a temp switch on the lower hose that comes on at 85ºC, yesterday it was only hooked to a continuity tester inside the car so I could see if/when the sensor would read. Mechanical fan w/clutch was installed + apparently working.
With an electric fan switched to come on at 92ºC (I tried that), rad exit temps will climb rapidly to 92º at traffic lights, sending the temp gauge half way between the center dot and the red zone while idling. If fan doesn't come on, of course temps will go even higher till something gives way.
I'm resetting my e-fan to come on at 85ºC instead of 92ºC. Hopefully that will keep things OK. Testing of the mechanical fan yesterday showed that I could not get the rad exit water up to 85ºC no matter how I drove or idled the car - including accelerating up highway hills.
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when its africa hot out and air cond turned on, i can pop the hood and see the clutch engage and kick into high with a woooosh. not to sientifical i know. good luck
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I did a search on this board on "Fan clutch" and found a number of posts, and enough opinions to start a small country. You should do the search and read all you can.
Interestingly, the fan clutch is mostly freewheeling at normal operating temps. It firms up to drive the fan if overheating. Or at least it's supposed to. But if you stop the car when overheating and spin the fan by hand, it may (or may not) have already cooled off so that when you spin it, it may or may not be stiff.
One post mentioned that the air flowing over clutch is part of the design. If rad is blocked up w/dirt, the airflow is impeded, causing clutch malfunction, apparently. Also causes poor radiator performance if blocked up.
You can also look for oil leaks on the clutch.
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Trev
As you know, I run a B21A in Australia. I was not 100% convinced my original Fan Coupling was doing the job. I came across an Aisin Seki, at my friend's Wrecking Yard. I replaced it. Additionally, I sealed the radiator to the body, using rubber "pinch-weld" kind of like automotive door weather-stripping.
The Temp gauge Needle always sits at or slightly below 9:00, occasionally slightly above . . . Choke/Mixture related.
The Fan, when Cold, seems to be stiff. When first running, after start, in two minutes or less, the Fan noise gets quiet. I seem to recall, after driving around, during Summer Down Under, the Fan still spins freely. I will let you know in December, for certain.
http://bartonharness.com/TropicalFanClutch.html
Other possibilities: Thermostat, Temperature Sender, Induction Air Pre Heat Open
Hope this helps.
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