Information from a list member on tearing the motor apart and repairing:
The fan will come apart pretty easily and can usually be rescued from an early (and expensive) grave.
- Remove the fan from the radiator and take off the plastic blade assembly.
- Locate and remove any locking rings and screws to allow separating the halves of the motor.
- Clean and lubricate the bushings, check the brushes and commutator and reassemble.
- 50% chance it'll work like new if you've never done it (90% if you've done it before).
The fan motor is a "pancake" design with flattened armature windings to allow for a shorter motor. I think the brushes contact the rear face of the commutator which is different than most DC motors you'll see. This makes disassembly and reassembly much easier.
Be careful with solvents around the motor... Harsh ones will remove the insulating varnish from the windings destroying the motor (don't ask how I know this). I use synthetic motor oil/Duralube mixture (50/50) when lubricating sintered bronze bushings. Doesn't dry out, and even if it does the Duralube should keep things happy.