We recently expected a spun rod bearing on a buddy's car and were advised to 'try' pulling the sump cover, rod end and bearings and cleaning up the journal with some fine emery paper.

The idea is that as long as the surface isn't actually damaged the only problem is some left over bearing material on the surface. The emery cleans this off.

New bearings and you are as good as new without major surgery.

Turned out the clunking was the air con compressor.