BMW part number 11 52 1 723 921 (11521723921) is the Fan coupling (&S), a cooling part catalogued for the E12 (528i, 525, 535i), E21 (320, 323i). As of our last check (2026-10-08, bmwpartsdeal.com), it has been superseded by 11521723918. Interchange records list it on E28, E24, E23, E30, E36, E34 as well. 2 repair guides below.
Replaced by 11521723918. Order the newer number.
No sourced aftermarket equivalent recorded yet. We only list brand numbers that a brand catalog or vendor page explicitly cross-references to this BMW number.
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Older numbers on the left, newest on the right. Numbers without a record open a lookup.
Listed directly for E12 and E21 in our data (see Fits). Models below are other listings of the same number.
Same BMW part number, but the source list is truncated or market-specific. More models may apply.
+23 more models not listed by the source.
No forum workaround recorded yet. If you know a thread, the hunt team wants to hear about it.
No kit or reman service recorded yet.
No DIY route recorded yet.
Write-ups and videos from owners, forums and specialists on removing and fitting this part. Summaries are ours; follow the link for the full steps, photos and torque values, and credit goes to the original author.
How to spot a failed viscous fan clutch (temperature climbing in traffic, a hot fan that stops easily) and swap it: shock the 32 mm left-hand-thread nut loose with a hammer on the wrench, then move the blade over with its three Allen screws. Also peeks inside the old clutch at its fill hole.
Tools mentioned: 32 mm box wrench, hammer, Allen keys
Photo procedure for refilling a tired viscous fan clutch with fresh silicone fluid: clip out the bimetal strip and pin to reach the fill hole, refill, refit. Written on a Porsche 928 clutch that the site says is the same design as BMW's; a salvage option rather than an OEM repair.
Tools mentioned: Small screwdriver, C-clamp, silicone viscous-coupling fluid
Written on a Porsche 928 clutch; principle stated to apply to BMW units.
Successor 11521723918 listed at $256.94 on bmwpartsdeal (InStock).
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