Marklin Z locos with side rods include examples from all three types of locos: electric, diesel, and steam. Before attempting to dismantle one of these locos please be sure of the pitfalls: usually these locos have numerous wheel sets and gears of varying size with side rods permanently mounted to two pairs of wheel sets and the challenge will be reassembly. Most of the time cleaning the wheels and a little oil will be all that is needed, but a fully cleaned and re-oiled loco is sometimes required for those trains that have either been stored a long time and have HOS (hardened oil syndrome) or run a lot and just need a deep cleaning. There are fewer service centers in the United States than there used to be and far fewer that are qualified to work on these types of locos. A long time local and exclusive Marklin dealer has never offered service on these types of locos partly due to the numerous small parts. One day I plunged in and discovered that logic bears out, and  it is possible to repair these beautiful little machines. Nothing will fly out once you have taken off the oil pan except coupler springs, wheel sets and gears may roll away so bearing that in mind keep track of each part and place in a container. Next thing to keep in mind is time, you may need to take apart and put back together again several times to make sure everything runs smoothy: side rods should have no tension when you are assembling, if they are bound up the two pair of wheel sets have not been placed correctly in relation to the distance between the axle grooves in the chassis. With the SBB Krokodil the side rods from each articulated end need to be positioned in correct relationship otherwise the loco might run well in one direction and not so well in the other. When the oil pan goes back on the following factors have to be satisfied: gears and wheel sets in correct position with wheels engaged with electrical contacts, pilot wheels were applicable need to in place, and springs and couplers installed. *Keeping it all together for attaching oil pan is a test of patience and resolve, but sometimes we have no choice but to proceed. This repair follows a logical course that will be apparent soon into the repair. Recommendation: try this repair on a less important loco in your collection to use as practice or one you bought in poor condition on Ebay. Do to the many variations of side rod mounted locos I have opted for a more general approach to this topic, for those who venture here patience and logic will get you through.