Rear Main oil Leaks.

[John P]

My Ulsteroid is fitted with an early coil engine and has always had an issue with oil leaking from the rear main bearing but this has now got a lot worse.

Although I built the engine myself some years ago I can't really recall how the rear bearing is sealed and it looks as though it could potentially be either a felt seal or an oil thrower which, as I understand it, directs any oil into a cast aluminium cover from where it drains back into the sump.

If it is this oil thrower set up then I'm at a bit of a loss to understand why it would get much worse relatively quickly.

As I've hardly driven it for 2-years now and every time I do so another problem arises I really don't want to take it off the road and strip it down yet again unless I have the parts I need to hand.

The engine number is M 132714 which I think means it probably dates to 1929 or 1930 but would anyone be able to date this more exactly and / or guide me on the likely parts required?

I'm fairly sure it is oil from the engine rather than the gearbox as it's very black as it trickles onto the garage floor.

John.

[Howard Wright]

Hi John

The engine number suggests March 1931.  The original rear main seal would be felt and thrower.

On the three engines I’ve built that date from this time I’ve replaced the bearing cover with one machined to take a lip seal. Readily available from the Cherished suppliers.  I’ve not needed to fit a speedy seal on the flywheel boss to ensure a good surface for the lip seal but I know others have. Touch wood I’ve had no leaks so far.

Unfortunately it is an engine out and flywheel removal job.

Cheers

Howard

[Murphy]

John,

This engine will have a conical oil thrower which needs to be 'nipped' between the inner rear main race and the boss on the flywheel, if it is to effectively work.  Are you sure that the oil is not coming from the gearbox front bearing?  I think that oil mixed with clutch dust may be 'blackish' and give the impression that it originated from the engine.

[Howard Wright]

Hi John and Murphy

I’ve just checked the source book and the felt seal was replaced by a spiral groove in the cover plate in 1929.

Cheers

Howard

[Terrytuned]

Use a Viton seal (red/brown colour) as these are much better than the Nitrile seal (black) A7 components stocks them BB7d high speed lipseal. Terry.
Note. use the oil thrower as the rear seal on its own won't cope with all the oil thrown at it.

[John P]

I've just been out into the garage and had another look at the leak which unfortunately is only really obvious immediately after I've been for a run and then parked up.   This means you don't get much of a clue by placing paper under the engine and looking for evidence.

The oil certainly seems to be dripping from the hole in the bottom of the bellhousing which, combined with it's black colour is what made me think it was from the rear main.

There is however also some evidence of oil along the back joint between the sump and crankcase and around the sump fixing screws at this point.   I have recently fitted a silicone gasket here but there is a possible issue in that one of the tapped holes which take the sump bolts has a sheared off bolt in it and to overcome this another hole has been tapped next to it and an additional hole drilled in the sump to line up with this.

This means that two of the sump bolts along this flange are further apart than they should be and then the next is closer (if that makes sense). This also means there is an unused mounting hole in the sump flange but presumably the silicone gasket would seal this off. 

Before taking out the engine yet again I wondered of oil leaking from this joint could be trickling down onto the lower edge of the bellhousing and then, when it reaches the drain hole, forming a larger "blob" which drips on the floor.   I'd really like to eliminate this before going any further so can anyone suggest how I could be certain where the oil is coming from.

I did consider either wedging a piece of plastic tube into the bellhousing hole and running this away from the area or temporarily blocking the hole but I'm not too happy about this as I guess oil which couldn't drain could potentially be thrown over the clutch.

John.

["Slack Alice" Simon]

I'd guess it is engine oil out the back of the engine, not the sump ....... but

Have you checked the level in the engine?   Of course you have.    If the engine has had a chequered history - see the broken sump stud left in, not dealt with - is the dip stick the correct item?

Is the gearbox oil at the correct level?   There is extended correspondence about this on the Forum.   It is easy to put too much in, err towards too little, if not sure.   For certain, too much

leaks out.

Why would it get worse, suddenly?   Are you sure about that, you don't seem to use the car a lot.   Did you top up sump and gearbox - see above.

Maybe the oil thrower has stopped rotating effectively: flywheel loose.   I'm sure you would have noticed that.

Crankcase pressure increased a lot?  Take the oil filler cap off whilst running - can you feel pressure?

Just some thoughts.   I'm afraid my attitude to oil leaks, when pointed out by passers-by, is: "Oh good, I thought I'd forgot to top it up!"

[John Mason]

Hello John P. If it was my car I would leave things as they are for now and keep running your car but checking the oil after each run to establish how much is leaking out. Clean all around the sump and bottom of the bell housing after each run to check to see if there are any traces of oil from around the sump. Rather than bell housing. Should it be the oil thrower that’s the problem on my two bearing Ruby engine I fitted one of the modem lip seals with a seal and adapter plate from A7 components without the need for an machining.

John Mason