Black Oil

[Bob46320]

1979 Mini 1000
I change my engine oil well before it gets black, but there is always a leakage of BLACK oil from the left hand side of the transmission case. I would guess about a good thimble full each week. It's difficult to locate but as best as I can see its from the drive shaft seal. My question is why is it BLACK and not the colour of the "clean" engine oil.
I replaced the gaters on both the inner and outer CV joints about 1000 miles ago and they are not split and look in good condition, so I don't think it's the CV grease.
Any ideas ?
Bob

[Peter Laidler]

I'd get back to the very basics Bob. First, you've GOT to find out where the oily stuff - whether it's oil or oil mixed with black graphite grease - is leaking from. Put a sheet of clean newspaper on the floor under the appropriate side. Liquids always drop vertically. That'll identify the accurate (?) location and we can all take it further.

It seems as though you are disregarding some of the obvious before looking for the fault.

[Spider]

Maybe a wee bit of a long shot here. Since you are running Pot Joints, these have a plug inside them, like a freeze plug, between the oil side and the grease side. I've had quite a few over the years were this plug hasn't sealed, they are only dry pressed in. I take the pot off, take it apart, clean it, knock the plug out - if you put a drift down the shaft side and carefully knock it from that side, it'll come out - clean these parts up with thinners, then refit with Loctite 243. Refit and it should be sweet. I now do this as a matter of course will all new Pot Joints.

If you pry back the CV Boot, you'll quickly establish if there's oil in there along with the grease.

[woodypup59]

Is the black rubber dust from the oil seal wearing ?

[Bob46320]

It doesn't look like the oil seal is dry and rubbing - ie no rubber dust there. The Pot joint gaiter on the LHS is always wet with the oil and from what you say, this may well be the cause of the leak. It begs the question - "why is there an oil passage from transmission to the drive shaft if it is plugged up" ?
Has anyone a drawing of the extractor tool so I can knock one up on the milling machine.
Then it take it all out, clean it up, attend to the plug (If its missing, are they obtainable, else what do they look like and can I turn one up on the lathe). Oh and fit a new o/p seal for good measure.
Thanks for the ideas and we will see where this leads to.
Bob

[floormanager]

Maybe a wee bit of a long shot here. Since you are running Pot Joints, these have a plug inside them, like a freeze plug, between the oil side and the grease side. I've had quite a few over the years were this plug hasn't sealed, they are only dry pressed in. I take the pot off, take it apart, clean it, knock the plug out - if you put a drift down the shaft side and carefully knock it from that side, it'll come out - clean these parts up with thinners, then refit with Loctite 243. Refit and it should be sweet. I now do this as a matter of course will all new Pot Joints.

If you pry back the CV Boot, you'll quickly establish if there's oil in there along with the grease.

I had this with one of my pot joints 40 years ago.

[Spider]

Here's a cross section of the joint;-



The Plug in question is on the left side.

And a Joint with the Plug removed;-



I can't recall the size of the plug off the top of my head, but I found them an odd ball size that I couldn't buy.

To remove the joint, be mindful that when it's removed, the oil in the engine will pour out via the oil seal on the diff side cover. If I'm not changing the oil, I just jack up the side that the joint is to be removed from to about 400 - 500 mm, tilting the car. I then remove the drive shaft out of the joint, it has a C Clip similar to the outboard end, though you would have had that apart when you changed the boots. There is also a similar C Clip on the Diff Output Shaft. While there is a tool for removing the joint off that shaft, I don't like them as if the joint doesn't want to come free easily, you end up smacking the tool hard against one of the diff side cover bolt heads very hard, not doing the gearbox case any good in the process. These days, I use a length of 1/2" steel rod, about 4' long, come in behind the engine from the top, until it lands on the edge of the pot joint being careful that it's not on the diff side cover, and then give it a good smack, the joint then should come off the diff. If you don't have a long length of steel rod, a short stout drift working from under the car also works, I did them like that for about 35 years years.