AFM to filter housing reservoir elbow had become separated due to loose clamp (glad I'm the mechanic to blame) so the oil was dirty. Fixed clamp, changed oil and filter, replaced fan clutch with new Sachs unit.
The old one was certainly not the Sachs, and although I don't know how they performed differently at 170 degrees and 2500rpm regarding slip torque, but at ambient 72 degrees and 5-20rpm they displayed substantially different breakfree and steady-slip torque values. If the photos appear correctly, one will be able to note the different fin pattern among the units and that the Sachs unit was 1mm thicker at the fan mounting position than the unit replaced. I suspect that after a year it can be difficult to determine which unit is the Sachs, so maybe these photos would help someone in the future looking at a used part...
Non-sachs unit, rear:
Sachs unit, rear:
Non-sachs unit, front:
Sachs unit, front:
Non-sachs unit, side, thickness ~12mm:
Sachs unit, side, thickness ~13mm:
More fan noise is evident with the Sachs unit, but since it was 72 F or below after fitment, more cooling is expected at idle in summer traffic but not yet confirmed.
The anti-seize lubricant fitted to both the bolts attaching the fan to the clutch and the clutch to the WP certainly did their job nicely, what a breeze to R&R for some un-anodized machined and threaded aluminum in an area of salt spray blast and many heat cycles.
