Just took the restored MK 1 Sprite out for it's first drive, leaked a litre of oil in 20 miles. The leak seems to be at the rear of the engine.

The engine was rebuilt by unknown persons, and I replaced the pan seals as the pan bolts were too long and the pan was not fitting snugly to the block.

I remember these engines had a problem with oil leaks from a tin can on the engine plate that was silver soldered to the plate.

There is oil coming out of a hole in the bottom of the bell housing, which would indicate the rear main seal is leaking.

I am going to pull the engine to try and find the leak but any wisdom from the Locosters would be greatly appreciated as it has been a long time since I played with these engines in a Sprite and two Minis.

Sounds like the rear crank seal to me.
I had a similar issue with my MGB when I changed the motor from a 3 to five bearing. The 3 bearing motor does not have a seal and relies on a reverse screw on the crank to return the oil to the sump. I had to get the end plate turned out to fit a crank seal.

David

The rear crank seal works on a worm effect if I recall correctly in the worm throws oil back into the sump this should have a piece of hemp like material wound round it as the seal. a lot of people disregard this because they dont know what it is

Hope you get the leak sorted, this thread has set the hairs up on the back of my neck - Mini oil leaks takes me back to my one and only Mini in 1984



Apart from getting his daughter pregnant my Mini always dripped on his driveway, only adding to his hatred of me. EEek memories..

As others have said, the rear oil seal is just a scroll seal. There are I believe kits that will allow you to fit a proper seal to it, but I don't know the details as inline A series was my mates area and I did the minis.

Hi, I worked at the factory in after sales support at the time of these motors and we had heaps of problems with the rear scroll leaking. Almost every one of these was down to poor engine breathing. Piston blow by and poor breathing lead to crankcase pressure and the poor old scroll was easily overwhelmed.

The fix (bodge?) at the time was as follows: First off to establish if the crankcase pressure was positive or negative was a highly sophisticated measuring device. Remove dipstick and push a clear plastic flexible tube into the hole. Form a U with the tube and add a liquid. Usually water as it rarely got sucked into the motor

Start the engine and observe the pressure under various conditions. Usually the water was pushed outward by the positive crankcase pressure.

The fix back then was: Inside the breather tube leading to the inlet manifold there is (was?) a small restrictor to limit the vac and avoid oil pull over. We'd pull out the restrictor and drill out the bore progressively until we had a good negative crackcase pressure. In 99% of cases this cured the leak.

Even if you don't have the restrictor, the answer is almost certainly in the breather system. Internal collapse of old tube, missing tube, holed tube...... A feast of choices.

Lastly, fitting a seal somehow should not really be necessary and will still potentially leave you with leaks elsewhere if you still have positive case pressure.

Hope this helps,

Mike

Mini's leak oil, its how to keep the bulk head rust free

It could be from various places including the gear selector leaking down.

All you can do is clean it all up, get it on ramps, start it and see if you can see where its leaking from.

Replacing all the old and perished hoses will help as well.