Rear main oil seal

[trouty54]

Hi Folks

I've been working on a 68 Minor which a good friend has just purchased. It's had a substantial restoration and is fitted with a stage 3 1275 engine and MG midget gearbox. I've sorted most of the issues it had, but there is a fairly substantial oil leak coming from the drain hole in the bell housing. Clearly this is the dreaded crank seal.

I'm based near Epsom Surrey, so can anybody recommend someone who can help?

Cheers. Trouty.

[svenedin]

Are you sure it’s engine oil? A leak from the gearbox front cover will also drip from the gearbox jiggle pin drain hole.

Unless it was fitted later, there is no oil seal as such at the rear of the crankshaft. It’s a scroll that throws the oil back. As for the gearbox front cover, again this is a scroll unless it has been modified to have a lip seal. The lip seals can leak torrentially if they suddenly fail and a car on last year's Minors on Tour to France didn't make it back to the UK for that reason.

I’m in South Croydon. I have a 1969 convertible.

Stephen

[King Kenny]

Before you jump in, have a look at the engine breather system. Mine engine leaked badly as you describe and i thought the same as you. However I checked the engine breather pipe and found it to be blocked with crud. After cleaning it out there was no more leaks

[svenedin]

Very good point re breather. If blocked the engine can leak very badly. What breather system does the engine have? As the 1275 does not have pushrod covers, the breather is usually on the timing chain cover with an oil separator can. This can become completely clogged rendering the breathing system useless and then there is no venting of crankcase pressure. Well actually there is venting of a sort, loads of oil leaks! Even the rocker cover breather (if present) can be completely blocked.

Stephen

[trouty54]

Thanks guys.

Firstly, yes I am sure it's engine oil.

The breather system vents from the crankcase to a 2 port catch can, and another from the valve cover. Everything is clear and working OK. Nothing that would cause excessive crank case pressure. The valve cover cap is also vented.

I have read a fair bit about the scroll type oil thrower, and assume therefore that it's not working as it should. I have no idea whether it has had a modified seal fitted without dismantling everything.

I'll post acouple of pictures of the engine compartment tomorrow, but in the meantime is there anybody you could recommend that may be able to help. I don't want to leave it and get the clutch contaminated with oil.

Cheers

[les]

I wonder if I have a similar problem, I used an endoscope in an attempt to find out where the oil comes from, the engine oil is the same as the gearbox oil, so you need to find out from which direction the oil comes from, gearbox front cover or scroll seal. I’m tempted to completely strip and rebuild the engine, to get rid or the problem once one for oil. Either that or fit a Japanese engine !

[mowogg]

Does the breather system via the catch cans vent to air or is it connected to the induction system?

[svenedin]

Does the breather system via the catch cans vent to air or is it connected to the induction system?

Exactly. If it vents to air, the best it can do is equalise to atmospheric pressure. It’s supposed to be connected to the induction vacuum. It sounds like a home-made system as it would never have had a "catch can".

As to engine oil or gearbox oil, if it is black then it must be engine oil but if it is clean it is hard to tell because the engine and gearbox use exactly the same type of oil.

Many of the aftermarket scroll to oil seal conversions do not work and persistently leak. An engine in good condition with a decent breathing system should not leak any oil with the original scroll. As the OP says, there's no way to know what's there until the engine is out.

Regarding who can help: I am not aware of any Morris Minor specialists near Epsom. Chertsey Minors have closed due to retirement. There are generic classic car garages in the Epsom area but I have no personal knowledge of them. Morris Minor Workshop in Stonegate, East Sussex is the nearest car specific specialist. They will collect cars if necessary (for a fee per mile of course but this is reasonable).

Stephen

[trouty54]

Here you are chaps. See photo.

The crank case vent and the rocker cover vent both go to the catch can. The rocker cap is also vented.

You will see that there is a white plastic elbow which takes vacuum for the power brakes. There was a 'T' here and a pipe going to a PCV valve on top of the catch can. The vacuum at idle was pulling air through this valve and making it impossible to tune the weber carb. Having now isolated that PCV the car runs like it should (especially at idle) and that problem is now sorted. I've fitted a filter at the top of the can. This has made no difference at all to the oil leak.

[trouty54]

Quick update. I've just found this photo which is one of many that came with the car. Looks like it's had one of the rim seals fitted like this one.

https://www.youtube.com/watch?v=bnOPAlVDcME

[philthehill]

You appear from the photo above to have a 1275cc flywheel fitted.
The lip seal kit is not engineered for a 1275cc MG Midget/Sprite engine as to get a surface for the lip of the seal to run on a spacer is fitted between the flywheel and crankshaft. This lifts the flywheel off the crankshaft register and allows the flywheel to move.
The outer face of the 1275cc Midget/Sprite crankshaft onto which the lip seal runs is not surfaced ground so the seal does not last long.
I will be perfectly blunt with you in that you need to get rid of the lip seal kit and go back to just having the oil return scroll. If you do that you will not have any trouble with crank case pressure or oil leaks. Having experience with this type of lip seal and the problems that go with it I could not wait to go back to the original BMC/BL set up. Unless you fit a properly engineered seal kit to the rear of the 'A' Series (i.e. the MED kit) you will always have a problem with oil leaks.
In my case I have a breather on the front timing chain cover, the rocker cover and the redundant fuel pump aperture. All three breathing pipes end up in a catch tank with a sight glass and I have never had any oil displaced or leak from the crankcase/sump gaskets. The rear of the crank has the return scroll and nothing more.
Having watched the video it makes me squirm when I see that spacer being fitted with no thought for the flywheel to crankshaft register. The register is there for a purpose not just to make it look good.

[trouty54]

Thanks for your advice Phil. I will look into the MED kit.

[svenedin]

Save your money, take the ineffective seal kit off and go back to the original BMC scroll set up.

Stephen