Manual - Chapter 1 Engine

13. Dismantling the engine unit: removing bearings and oil seals

Note: All oil seals should be renewed as a matter of course whenever they are disturbed, but bearings should be disturbed only if examination proves them to be worn or defective. Proceed as described below but note that where instructions are given requiring the use of heat, castings must be heated evenly to the required temperature. This means using an oven, or placing the casting in a container and pouring boiling water over it (taking care to avoid splashes); do not use sources of fierce localized heat such as gas-powered torches. Always clean castings carefully and remove any components that might be damaged by heat before heat is applied, and always take precautions (wearing suitable protective clothing, gloves etc) to prevent the risk of damage or of personal injury when heating components or when handling them.

  1. The auxiliary driveshaft rotates on a needle roller bearing at the front in the upper rear part of the main crankcase/cylinder block casting, and on a ball bearing in the bell housing.
  2. If the needle roller bearing is to be renewed, it can be extracted using a slide-hammer with the correct internally-expanding adaptor; BMW recommend that the crankcase casting is heated evenly, in an oven or similar, to 100 -120 °C (212-248 °F) to permit the bearing to be removed. If these tools are not available, use a hammer and a small pin punch to drive in part of the bearing outer race so that it can be gripped with pliers and drawn out; be very careful not to damage the bearing housing and to collect all the pieces of the bearing if this method is used.
  3. If the rear bearing is to be removed, withdraw the retainer plate (held by three Allen screws) noting the conical spring washer behind it and carefully lever out the oil seal (see below) before withdrawing the locating circlip. The bearing can then be driven out using a tubular drift such as a socket spanner which bears only on the bearing outer race; note that BMW recommend the bell housing is heated evenly, in an oven or similar, to 100 -120 °C (212-248 °F) to permit the bearing to be removed. Clean all traces of Loctite from the threads of the retainer plate screws and their tapped holes.
  4. The output shaft front bearing can be pulled off the shaft front end by hand while the rear bearing will require the use of a bearing puller to withdraw it from the shaft, after the retaining circlip has been released.
  5. The starter clutch gear pinion rotates on two needle roller bearings. If these are to be removed they can be driven out using a hammer and a suitable drift; take care not to damage the pinion on any surface.
  6. If the output shaft rear oil seal is to be removed without separating the crankcase lower and main sections it can be levered out providing that great care is taken not to damage the shaft the seal housing or the crankcase around it; use only a tool with well-rounded edges and pivot it against a block of wood placed on the crankcase. Alternatively, two self-tapping screws can be screwed into the seal (as close to it outside edge as possible without marking the seal housing) to provide points which can be gripped with two pairs of pliers or similar so the the seal can be pulled out; take care not to allow the screws to touch the bearing.
  7. If the auxiliary drive shaft rear seal is to be renewed with the shaft removed it can be levered out. If the shaft is still in place, the seal can be pulled out using the second of the two methods described above.
  8. If the crankshaft front oil seal is to be removed from the cam chain (engine front) cover while the cover is still in place, it can be extracted using two self-tapping screws as described above. However, this seal is a tight fit and owners may find it necessary to remove the cover in order to renew the seal to prevent any risk of damage; note that refitting will be difficult with the cover in place. If the cover is removed, the seal can be tapped out using a hammer and a socket spanner or similar as tubular drift. In exceptional circumstances heat the cover by immersing it in boiling water to loosen t e seal's grip.
  9. If the oil level sight glass IS leaking or damaged it can be remove as follows from the crankcase lower section. Drive a sharp-edge screwdriver or similar into the sight glass centre and lever out the glass and seal, then withdraw the metal cage; this will have to be levered out, distorting it in the process, so care must be taken not to damage the housing. Use blocks of wood as pivots for the levers so that the crankcase fins are undamaged.

The history of BMW