Morris Minor Owners Club

i have quite a good oil leak from the back of my engine, it appears to be coming from the gap between sump and backlate. i put in a new gasket a few weeks ago and its still leaking. any ideas as to what else it could be?

Pressure in the engine - forcing oil out past the rear scroll. Hot engine idling - take the oil filler cap off and rev up - is there a plume of smoke/fume? What are the engine 'breather' arrangements?

when i rev the engine, no smoke or fumes are noticed. the engine as a breather pipe on one of the cam follower covers and the rocker cover is vented through a pipe to the air filter. i have checked the pipe and its clear and unblocked.

i have replaced the gaskets all around the engine when i rebuilt it earlier this year, so i doubt it could be a knackered on of those

Well - you need to decide if it's coming past the scroll - which would mostly appear in the gearbox bellhousing and drip from the split-pin hole, or just from the back seal on the sump. From your test etc - it looks like it could well just be the sump. Did you use a cork seal - or a rubber seal ?

i used a nice shinny new cork seal. with a little bit of gasket blue just to hold it in place

And - did you soak it in oil first -and leave it standing 1/4" proud on each side?

i didnt soak it in oil first, but i did leave about 1/4" at each end

quite a lot of sumps, they are just pressed steel after all, have a small raised or distorted areas around the crank ends. Its worth removing these with a file before fitting the gaskets.

Try running the engine with the car over a pit, having cleaned off all the oil and grud beforehand. This will help to locate the actual source of your oil leak(s). If you have to replace the sump gaskets, I would recommend using the spridget 1275cc synthetic rubber seals instead of the cork seals. This worked for me as I tried cork several times without success. I thoroughly cleaned and degreased all surfaces and used high temperature silicon allround allowing it to cure properly before starting the engine. On mine the leak was so persistant and I was so fed up and didn't want to take any chances for the sake of the cost of the silicon. It works perfectly but it may very well have worked without it. On the other hand, I have no intention of removing it again to find out! What is sealed is sealed and I'm relieved-and the neighbours too!
Hope it helps.
Regards

I have the same leak. Oil leaks past the sump/block seal at the back and dribbles down the back of the sump. The problem is the small cork strip that goes over the "hump" for the crankshaft.

At some stage I plan to drop the sump and replace the cork seals, but the leak is not bad enough to worry about at the moment. Just park on the grass

thats what i am thinking my problem is.

i have got new seals from esm this morning, and now got the cork seals soaking in a nice vat of oil (as per recommendation from bmcecosse)
also got new bolts and washers, so after a liberal smush of silicone stuff, it SHOULD stop the ruddy leak.

Don't be tempted to over tighten the little screws - they are VERY easily stripped!

Also, when the sump is off, do as Billoban suggests and check the area around the fixing holes is flat! Rather than filing, I peen them back flat with a light-ish hammer. Might not affect thhe present leak, but could prevent the sump joint weeping in the future.

just had a good luck under the car, and its not the sump. it appears to be coming from the back plate. considering that i put a new gasket there and new oil pump, i am hoping that its not them, any ideas what else it could be?

The rear scroll - due to pressure in the crankcase.

still not understanding how pressure in a crank case can cause a leak when my crank case is well ventilated through the rocker and the cam follower access cover event.

How well vented?? Something is pushing the oil out past the seal - it will be pressure. Possible of course that scroll and/or crank is damaged - let's hope not!

well the small leak has turned from a mild annoyance into a large problem, i have left a stream of oil down the road to my house and used up 1/8th of the sump contents.

so, i regretably now going to whip out the engine and gearbox, replaced the backplate seal and the oil pump gasket. i will also turn over the engine and put the new sump gasket on.
i will also check all around the ventilation, and remedy is needed.

other than that radical solution, i am at a loss how to remedy this

Refresh my memory please! Did you fit all new pistons/rings to your engine when you built it? It sounds horribly like it could be a broken ring. As Roy says, something is pressurising the sump. With a newly rebuilt engine this wouldn't neccessarily be evidenced by blue smoke etc if just a ring has broke. The scroll seal is not something that is going to wear quickly or significantly if you have recently fitted new shells. Sorry to be sounding gloomy, but I've been there myself

when i rebuilt the engine in early january, or late december ( i cannot remember) it was new pistons, rings, gaskets, big end bearings and clutch. the engine worked perfectly fine before i overhauled it, but since then its had abit of an oil consumption problem.