The Mk4 Fiesta includes those cars built in the early 1990s, specifically from 1991 until 1995. Being relatively cheap to buy, run and insure, these cars are often picked as first-time buys. Many motorists, having spent all their money on their first car, will hope to save some money by attempting repairs and maintenance themselves1.
The gasket on a Mk3 was a reasonably simple all-in-one design. However, after 1991 it was changed to be a four-piece design. Coupled with major design flaws, this makes changing the sump a very unenviable task.
The first problem is simply getting the sump off2. Because of the cramped design of the engine, of the 15 nuts that need to be removed from underneath, at least three are inaccessible without some seriously good ratchet equipment. Also, in order to remove the sump the alternator must be removed, thereby increasing the complexity of the task. With this in mind it is advisable for the do-it-yourself (DIY) mechanic to allow several hours to change a gasket while on a drive.
Once the sump has actually been removed the fun begins. Firstly you have to remove the old gasket. This has probably been on the sump for some time and will be caked on well. Years of heating up and cooling down will mean that the sealant is baked onto the sump, and this will need to be completely cleaned off. This is easy on the part of the sump you remove, and can take away from under the car. The part still under the car is a nightmare to clean.3
When the sump has been properly cleaned on both sides you are ready to fit the new gasket. This is where the first major design flaw becomes apparent. The two pieces of cork gasket, which sit on the top of the piece you have removed, are simple to fit. However, the two semi-circular rubber seals are a different matter.
In their infinite wisdom, the Ford engineers decided to place a small 2mm metal ridge where each rubber seal has to go. Unfortunately, there is no groove within the rubber to rest this on. Consequently, the rubber gasket is balanced precariously on this ridge. This is where the fun starts, because in the limited space under the car one has to manoeuvre the sump into position without these rubber gaskets touching anything4. Even a sudden movement can cause them to be knocked off in to the sump itself, which of course means getting out from under the car and starting again. Very irritating.
After about an hour of trying unsuccessfully to get the sump back in place the average DIY mechanic would by this point be using plenty of swearwords against Ford, but with enough perseverance and a little luck you will get the thing back on.
Once it is back on you have to be careful to tighten the nuts in a specific order, otherwise the seal might not be tight and thus your car will leak oil. Once done, heave a sigh or relief and think about the pretty significant amount of money you have just saved yourself by not taking the car to a garage! (On the other hand, you have just wasted a whole day).