Rear Engine Oil Leak

[David53]

Well, car is running well with rebuilt Dizzy and happy to report not a single drop from the front Timing Cover seal

Still leaking from the back however. Not huge amounts but would like to see if I can correct it if I can. On inspection it is seeping from the area where sump joins the block at the rear, as shown by arrow. I am surprised this joint does not seem to have a gasket???



I am assuming this is the dreaded rear engine scroll leak, am I right? I am aware that crankcase pressure can cause this. I think my crankcase pressure is quite high. Oil pressure is 60 psi at speed once fully hot and when engine idling you can feel the air pumping from the crankcase breather pipe. I also get a few drips from this pipe once the engine cools.

Rocker cover is connected to air cleaner via pipe (oil bath type cleaner) and some vapours come from this if removed when running.

Is there any way I can reduce crankcase pressure? Would fitting a later type oil cap with air vents be a good idea?

[bmcecosse]

No! If you vent it like that - you will breathe the fumes and they are not good for health! You must suck the fumes into the inlet manifold - it's the only way. Either use a later carb with direct connection on the side - or make a tapping into the inlet manifold - with just a 1/8" restrictor hole - and connect the rocker breather to that. It may upset the idle slightly, although you can usually adjust that out. Other than a rebore/new pistons etc - this is the way to eliminate the crankcase pressure. It has nothing to do with oil pressure - which looks fine!

[David53]

Thanks BMC. The leak is not major, it's about a two inch pool on the drip tray after a really long hot run. I'm not going to lose too much sleep over it (after all, Morries do leak!) but might consider tapping the manifold as you suggest. I doubt the oil bath air cleaner is doing much sucking at all!

Should I be at all concerned about oil getting into the clutch? I do recall the housing around the oil pump on the back plate was re-soldered when the engine was re-assembled.

[bmcecosse]

Yes - if a LOT of oil comes past the labyrinth 'seal' - it can muck up the clutch and the starter bendix. Is it leaking from the split pin in the base of the bellhousing ? If it's just running down the back face of the sump - it may be just needing a new cork seal on the back edge of the sump.

[David53]

Well I think there are two leaks - the rear cork seal on the sump is dribbling a small amount (why doesn't the rear cork seal show in the parts diagram I wonder???) and there is a drip from the split pin.

The drip from the split pin is not huge, prob about 4-5 drops after a really hot run (did 70 miles today of fairly hard driving on a 35 degree C day). On my shiny drip tray it results in about 2 inches diameter pool once it has spread out. Is this enough to be worried about clutch getting contaminated?

[bmcecosse]

Probably not. Only time will tell. There IS of course a cork seal at the rear - it must be left nice and long so it compresses as the sump is bolted up.

[Declan_Burns]

David,
I had the same problem and I wrote this on an earlier thread:
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. Thoroughly clean and degrease all surfaces and use high temperature silicon allround allowing it to cure properly before starting the engine. Check also the tappet chest seals. Again could be cork but there are modern neoprene seals available. Otherwise as above.
Hope it helps.
I also fitted the OB rear seal mod-but that means gearbox or engine out. I would try sorting the breathing first as Roy has mentioned.

[bmcecosse]

The 1275 sump has larger diameter ends - to suit the larger main bearings - are the seals pre-formed ? Mini ones are - but slightly different arrangement. If so - wont' fit the smaller sump. I have used silicone rubber - square section - in there before, but nothing really wrong with the cork - provided it's fitted properly - left long so it compresses down.

[Declan_Burns]

The 1275 seals have to be cut back slightly-takes only a few minutes with a hacksaw. There is a wire insert which is best dressed with a file after cutting. They fit very snugly. It certainly solved my problem. I could not get the cork to seal and after several attempts finally used the rubber. Some have no problems with the cork.

[aupickup]

you only need to leave about 2 to 3 mm of cork or rubber over the sump , much longer and the sump gasket will not seal properly

[bmcecosse]

I agree to be careful with rubber - but the cork will compress down if 5/16" is left raised at each side.

[David53]

Have ordered a sump gasket set. Might as well at least cure that leak

Page AA26 of the manual says the cork packings should stand proud no more than 1/8" or they will spread and prevent the sump from seating properly. They also say to grease the cork packings - should this be with standard bearing grease? And finally, should I use any gasket sealant on the side gaskets or just leave them dry?

[PSL184]

With cork gaskets I always soak them in water first *. I find (and others will no doubt disagree) that they are a better fit and stay in place if they are allowed to swell up first. Then rub a smear of normal grease over both sides of the gasket (leaving 1/8 - 1/4" proud of the sump each side) and refit the sump tightening the bolts evenly, a little at a time in a rotational manner similar to how you do head bolts. Do not overtighten the sump in the same way as you would not overtighten the rocker cover. I always do it this way and I've never had a leak.....

* The water opens the cork structure. As the water dries out it gets replaced with oil from the sump and is retained by the grease on the gasket. This forms a natural barrier to prevent leaks (my theory anyway ? )

[David53]

So grease on the paper gaskets? Not a sealant?