THE MINI MAG. Volume 2 No.7
  July 2000

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HELPFUL HINTS and IDEAS.
By Jim Haydon.
The following articles are sourced from personal experience, experiences of others, plus publications by B.M.C., Leyland, Rover, Scientific Publications, Australian Classic Car, U.K. Practical Classics, Sports and Classic Cars Aust., Paul Hamlyn, Gregory’s Publications and others.
THE MINI OIL LEAK.

POTENTIAL LEAKS:
1. Front timing cover seal. This can be inside or outside the cover. Depends on the model.
2. Front timing cover gasket.
3. Front engine plate to block gasket. (especially prevalent on 1100 / 1300 4 doors)
4. Rocker cover gasket.
5. Rear inspection plate gaskets. (push rod and cam follower covers)
6. Cylinder head gasket.
7. Rear engine plate.
8. Rear oil seal. This is in drop gear case.
9. Drop gear case gasket.
10. Gearbox to engine gaskets. Differential to gearbox gaskets.
11. Front of gearbox to engine block sealing strip. *refer d & e below.
12. Speedo output drive.
13. Left & right driveshaft output seals.
14. Gear selector rod. (Clubmans).
15. Distributor.
16. Oil sender switch or capillary pipe.
17. Breather outlets.
18. Oil filter and oil cooler lines.
19. Crankshaft plug. Early 850’s had a secondary plug.

WHY LEAKS OCCUR.
a. Oil leaks are made worse by increased crankcase pressure. This can be caused by worn or broken rings, blocked breather outlets, or even too much oil in the engine.

b. Most oil seals have just become hard with age. Worn bearings, especially mains, aggravate leakage and seal wear. In extreme cases the hardened seals score the contact area on the crankshaft. When replacing, reposition the seal lip to an unscored area.

c. When assembling an engine or gearbox use new gaskets and thinly coat one side with silicon gasket maker. Ensure both surfaces are smooth and free of burrs. File level if necessary. Top mating surfaces of the gearbox are critical.

d. Very important! Front engine to gearbox sealing strip. Do not cut this strip! Clean the gearbox to seal contact area with petrol then coat with contact cement. Coat contact area of seal with the contact cement. Wait until touch dry and stick together. Coat top of seal and corners with silicon gasket maker. Do NOT use standard grade silicon! Standard grade silicon breaks down in contact with oils or petrol. Assemble gearbox to engine carefully and squarely. Torque bolts and nuts evenly.

e. Ensure all the correct bolts and washers are used on the timing cover. If long ones, or even the correct ones without washers, are used at the bottom they will push up hard against the gearbox and can force the coverplate away from the block causing an oil leak. When assembling a completed engine to a gearbox, the additional length of these bolts can dislodge the front sealing strip. You won’t know this until the engine is in and running and you find oil dripping out from behind the engine plate. If this happens, the engine must come out again and the gearbox and engine will have to be parted and resealed.

f. Rear oil seal. When possible mount output gear inside the cover when fitting. Do not forget the spacers! If fitting from the outside with the output gear in place, take great care. It is very easy to dislodge the seal tensioning spring. Clean out the oilways in the flywheel after replacing this seal. These oilways sling any escaping oil away from the clutch facings.

Jim Haydon.