I hope the audio comes through reasonably well on the video. The point in making this was to show the difference between engine noise (steady ~3000rpm) and the roar of the fan engaged at the same RPM. Anyway, here's a copy/paste from the video description:
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Testing the mechanical viscous fan clutch engagement is difficult. The "roar test" is the most valid method to confirm engagement but many people may not know what to listen for, or what it sounds like. In this video you can hear the fan clutch engage and start "roaring", which sounds like a small hurricane, at 3 different points in the video. Here are the timestamps:
0:08 - Engaged
0:18 - Disengaged over 3500rpm
0:35 - Re-engaged
0:42 - Disengaged over 3500rpm
0:52 - Re-engaged
This video is of a W124 with M119.974 engine and OE Sachs fan clutch 119-200-01-22. PLEASE NOTE that fan clutch engagement will vary based on ambient air temp, coolant temp, if the AC is running, and if the condenser/radiator fins are obstructed.
For this video, the AC was turned OFF, which resulted in coolant temps higher than typical when the fan engaged. With AC running, there is additional heat load from the condenser which will engage the fan clutch at lower coolant temperatures. Although in this video the clutch was fully engaged at 98C, under normal driving with AC on, it is typically engaged around 90C coolant temps. Normal summer engine temps on this car are 90-95C.
Keep in mind that the fan clutch engagement is not binary, i.e. on/off like a light switch. The clutch engagement is infinitely variable. When partly engaged the fan clutch may disengage at low RPM's, i.e. 1000-1500. As temps increase it will eventually remain engaged up to the 3500rpm mechanical cutout as shown in this video. If you slowly increase RPM's you can hear the roar stop when the clutch disengages.
Aftermarket clutches (not OE/OEM Sachs/Horton) may remain engaged above 3500rpm however the OEM clutch will always disengage at 3500rpm regardless of air or coolant temperatures.
It is very difficult, almost impossible, to properly test the clutch in cold ambient temperatures (especially near or below freezing). It's best to test on the hottest days of summer. For this video, ambient temps were 90F and I started recording around 90C engine temp. It took about 2 minutes holding the engine around 3000rpm before coolant temps increased enough at the radiator to engage the fan. I edited the video so you don't have to sit through 2 minutes of nothing happening besides engine temps slowly rising.
Some of the M119.97x clutches are mis-calibrated from the factory and engage much later than spec. I've performed this test with other clutches that did not fully engage until 105-107C coolant temp which is much too hot, the clutch should be fully engaged by 100C.
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Testing the mechanical viscous fan clutch engagement is difficult. The "roar test" is the most valid method to confirm engagement but many people may not know what to listen for, or what it sounds like. In this video you can hear the fan clutch engage and start "roaring", which sounds like a small hurricane, at 3 different points in the video. Here are the timestamps:
0:08 - Engaged
0:18 - Disengaged over 3500rpm
0:35 - Re-engaged
0:42 - Disengaged over 3500rpm
0:52 - Re-engaged
This video is of a W124 with M119.974 engine and OE Sachs fan clutch 119-200-01-22. PLEASE NOTE that fan clutch engagement will vary based on ambient air temp, coolant temp, if the AC is running, and if the condenser/radiator fins are obstructed.
For this video, the AC was turned OFF, which resulted in coolant temps higher than typical when the fan engaged. With AC running, there is additional heat load from the condenser which will engage the fan clutch at lower coolant temperatures. Although in this video the clutch was fully engaged at 98C, under normal driving with AC on, it is typically engaged around 90C coolant temps. Normal summer engine temps on this car are 90-95C.
Keep in mind that the fan clutch engagement is not binary, i.e. on/off like a light switch. The clutch engagement is infinitely variable. When partly engaged the fan clutch may disengage at low RPM's, i.e. 1000-1500. As temps increase it will eventually remain engaged up to the 3500rpm mechanical cutout as shown in this video. If you slowly increase RPM's you can hear the roar stop when the clutch disengages.
Aftermarket clutches (not OE/OEM Sachs/Horton) may remain engaged above 3500rpm however the OEM clutch will always disengage at 3500rpm regardless of air or coolant temperatures.
It is very difficult, almost impossible, to properly test the clutch in cold ambient temperatures (especially near or below freezing). It's best to test on the hottest days of summer. For this video, ambient temps were 90F and I started recording around 90C engine temp. It took about 2 minutes holding the engine around 3000rpm before coolant temps increased enough at the radiator to engage the fan. I edited the video so you don't have to sit through 2 minutes of nothing happening besides engine temps slowly rising.
Some of the M119.97x clutches are mis-calibrated from the factory and engage much later than spec. I've performed this test with other clutches that did not fully engage until 105-107C coolant temp which is much too hot, the clutch should be fully engaged by 100C.
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