Following a recent customer’s oil leakage problem, I have, with great cooperation from that customer, done some investigating in the area of the crankshaft oil seal.
It seems that there are two problems. Firstly, the oil seal is an imperial sized item with a 2” bore and it is designed to run on a 2” shaft - the shaft protruding from the Centa rotor, on which the seal runs, is only 50mm. therefore, 0.8mm undersize or 0.032” if you prefer. SKF, who produce this type of oil seal, recommend a much tighter tolerance in the region of plus 0 minus 0.01mm. The second problem is the surface finish of the shaft - as already pointed out on these pages - the finish is much too rough and in some cases badly damaged due to clumsy manufacture.
I have identified a cure for the problem for those wishing to use a standard Centa component. SKF produce a repair sleeve which can be pushed over a damaged shaft to bring the surface back to a useable state. Luckily for us it also increases the shaft diameter by 0.56mm bringing it much closer to the required 2 inches. The sleeves also have a surface finish designed specifically to promote good sealing and also good seal life. For reference if you are fitting one the seal lip and therefore the middle of the sleeve should be 15mm from the flywheel end of the shaft. The sleeve can be fitted complete after the alternator is bolted to the Centa rotor or, if you prefer, the flange can easily be removed from the sleeve and the alternator rotor fitted afterwards but be careful not to scratch the sleeve.
The old seals which I have examined after being used on the standard Centa shaft are all worn flat and need to be replaced at the same tome as the sleeve is installed - not expensive so no point in not replacing it.
A stunning virtual bevel box which demonstrates all this and also the very simple method of fitting using the tool supplied with he sleeve, can be seen here :- https://www.youtube.com/watch?v=wsIklI3xtME
SKF spec :-
Part Number: 99196
Type: Speedi-Sleeve And Tool Kit
• Flange Diameter: 2.2440 in
• Shaft: 1.9690 in
• Shaft From: 1.965 in
• Shaft To: 1.971 in
I hope this helps sort the problem for people. I have posted it as a new post and on the end of the thread about the problem