Coca Cola should work well. I'd also suggest vinegar. I'm using about 8 gallons of the stuff to clean brake drums on my Imperial - does a very nice job in about 72 hours. A few minutes with steel wool to brush off what the vinegar loosened and then dry (with alcohol) and paint as quickly as possible before the rust starts again (obviously no paint on you pan though )

jlc

__________________
Jeff

'87 560SEL 267K (177K on motor) Blue/Blue
'98 Buick LeSebre 60K (wife's car)
'56 Imperial Sedan 124K
Past Cars:
'67 Dodge Monaco 130K (Sold)
'87 Chrysler 5th Ave 245K and going strong (sold)
'73 Plymouth Satillite 175K (sold)
'96 Chrysler LHS 80K (totaled)