Crankcase oil leak- LD 150 '57

[rlpembridge]

Hi all,

I have been mystified for some time at a persistent leak of oil into the crankcase, evidently from the gearbox-side oil seal. I think I have now identified this to the machined faces of the dual-race bearing (Casa code: M207, Innocenti code: 11110326). I should stress that this leak presented itself only after I had replaced the gearbox-side bearing with a new unit, at the same time as fitting a new crankshaft.
I'm posting this to see if anyone else has experienced the problem and / or is aware of the following details.

The first evidence of a problem was a smoky exhaust and engine failure. I initially identified an oily spark plug. Strip-down of the engine then confirmed gear oil in the crankcase.
Comparison of the new and old bearings shows a visible disparity at the tapered / rounded edges of the outer shell. Measurement determines the overall length is exactly the same; 20.5mm. However, the new bearing (marked SKF), has a flat face at the ends of the outer shell with an OD of 45mm. On the previous bearings (marked RIVA), that flat measures at 44mm OD.
The OD of this bearing is 47mm. The ID of the machined 'stopping point' in the engine case (at the point of entry into the gearbox), is 44mm.
The consequence of this disparity appears to be that the leading edge of bearing is seating fractionally less deep into it's aperture, which in turn causes insufficient compression on the outer O-ring seal, thereby allowing oil to enter the crankcase, behind the flange plate of the main oil seal.

I read that RIV bearings initially merged with SKF bearings in 1965. SKF fully acquired control of RIV in 1979.

Before addressing this issue with suppliers, I'm keen to know if anyone else has had a similar experience, or even has RIV and SKF bearings they can test these measurements on?

Thanks RP

[jbcollier]

Can you post some photos? You list three different ODs (44, 45, & 47 mm) and we're discussing only two bearings (old and new).

[jbcollier]

PS: I built my engine up with all new SKF bearings, no issues.

[jbcollier]

I would suspect myself an issue with the drive side crank seal (11110351 - 31x47x7)

[rlpembridge]

Hi JB, I don't believe the oil seal or the outer O-ring are of themselves the problem - I have changed both, several times.

I have put an explanatory document together, with photographs, dimensions, my measurements and diagnoses but this platform won't allow me to upload it, with or without the photographs. I don't seem to be able to upload the photographs independently, either, so the text won't make sense without them.

Is the another means by which I can send to you, please?

[jbcollier]

[jbcollier]

I wrote:

The seal plate has to mate with the drive side crankcase face. Your measurements imply that where the plate meets the drive side bearing it is actually 0.5mm proud (!) of the seal plate face.
I don’t have a disassembled engine to examine so please forgive the potential silliness of my next question. What does the other side of the oil seal plate look like?

Richard replied:

Not silly at all, I’ve considered the same. The oil seal is designed to fit - and function - only one way.
I considered that the cut outs for the machine screws were also a big clue.

[jbcollier]

Richard wrote:

The bearing ‘protrudes’ 0.5mm from its 20mm hole in the crankcase.
The centre part of the oil-seal flange plate (against which the bearing makes contact), is 0.5mm higher than the area outside the lip.
That creates the total gap (between mating faces of the flange plate and crank-case), of 1mm.

Here are my measurements of the plate:
Oil seal flange plate:-
Height of lip:
2mm from outer face of lip.
1.5mm from inner, ‘bearing-face’ of lip.
OD of lip: 50.5mm
ID of lip: 47.5mm
ID of centre hole: 39.8mm
Thickness of metal at inner circumference of plate: 2.25mm.

I’ve researched available bearings. These deep-groove dual-race bearings are actually listed as 20.6mm wide.
There is no 19.5mm, nor 20mm alternative.

[jbcollier]

I replied:

Mine is a 1955 and had drive-side crank bearing retained by a circlip and then the seal in the same bore.

The piston floats on the rod and there hasn’t been a problem with the plate protruding too far and rubbing on the crank. The only issue is gear oil getting past the seal. Why not make up a 1mm shim that clears the lip on the plate and then seal that to both the case and the plate? Simple to make as 1mm plate is readily available. Problem solved and no funky machining required.

I thought of suggesting using gasket material but I’d really like to see metal to metal contact for the seal plate to the case to reduce the possibility of any flex and the plate retaining screws loosening.