17 replies to this topic

[mk=john]

Hi

I have just dicovered that the primary gear for my mini is leaking oil. The engine is a newly rebuilt 850cc unit on my 1960 mini. It has an early type primary gear wih plain inner and outer bush, and apparenly it is well known that these can leak. The engine builder said that I need to be careful and ensure that engine breathing is maximised to prevent oil leaks.

One of the tappet chest covers has a vent, into thin air, and the rocker cover has a breather pipe leading to the air cleaner box. This was the original set up on the car.

The engine has just been rebuilt, and the piston rings will likely need 1000 miles to bed in. Before then, could the engine currently have lots of `blow-by' past the pistons causing high crankcase pressure? Will this reduce once the pistons rings have seated properly?

If not, what else can I do?

Thanks
John

Edited by mk=john, 20 December 2011 - 10:37 PM.

[bmcecosse]

Yes - the breathing is ultra important. I know you want it be original - but the rocker breather would be MUCH better connected to the breather tube on the side of a later model carb. But it was only the really early Minis that had severe leak problems - with the small diameter crank tail. Is that the set-up you have - or the later/thicker crank tail with the Deva bush primary gear?

[mk=john]

I think the early type. The car is very original including this. I have the original carburettor and want to keep that on the car. I dont know where else on the car I can fit it???

Edited by mk=john, 20 December 2011 - 10:46 PM.

[bmcecosse]

Test for fume - hot engine and remove the oil filler cap - and rev up - is there a plume of smoke/fume??

If you read all the early Mini rally reports -they nearly all retired with oil soaked clutches. The early design was really really hopeless.... Once they had that sorted - they went a bit faster/longer and then the wheels pulled over the nuts (been there done that!) -so I hope you don't still have the original 'thin' wheels !

Edited by bmcecosse, 20 December 2011 - 10:50 PM.

[mk=john]

havne tried that yet, what will that tell me? If there is a plume then I take means the breathing pressure is high?

Edited by mk=john, 20 December 2011 - 10:49 PM.

[Ivor Badger]

The oil leak is not affected by the breathers. The only cure from the time was to change the primary gear and block the oil feed hole in the crank with the supplied brass taper pin. You got a new primary gear, oil seal and taper pin in the kit. Remember to remove the oil seal in the flywheel as the new primary gear has longer splines.

[mk=john]

So how is the new primary gear lubricated if the hole was bocked off?

[Ivor Badger]

So how is the new primary gear lubricated if the hole was bocked off?

The early gear uses white metal bearings, the later one uses Oilite and runs on the oil held in the bushes. They haven't fitted the oil feed hole since sometime in 1963, so I think the cure worked.

[bmcecosse]

Ivor - if there is excessive crank pressure it will blow oil out past the seal. But I agree - it's not the only source of oil in that area, which is why I asked about the deva bush. The new 'deva bush' primary gear was designed by Glacier to run without the oil feed. I used to make the deva bush at Glacier!
Here's a link to Somerford http://www.somerford...on-ShaftDri.pdf

Edited by bmcecosse, 21 December 2011 - 12:10 AM.

[Cooperman]

Right. The oil fed primary on the early 850 with the small diameter crank tail were always a problem. AS above, blank off the oil feed hole and replace the primary gear bushes with oilite or phosphor bronze to the same spec as the material used in all late cars. I think Mini Spares might be able to give you the exact material spec and you can then get some specially machined to suit.

[Ivor Badger]

thought all 850s used the same diameter crank at the primary gear.

OK, thumbs up all those that have actually changed the gear and blocked the hole

Edited by Ivor Badger, 21 December 2011 - 12:26 AM.

[mk=john]

OK
I will wait a litttle more time as it isnt giving any running probelms whatsoever, and the clutch is not slipping. But just a question regarding the primary gear. Can the primary gear be removed with the transfer case still bolted in place (only removing the clutch oil seal and c-washer??) or does the transfer case need to be removed?

Would the crank tail need to be measured accurately? (i don't want to have to remove the engine from the car!1) Or are these bushes standard sizes that fit straight away?

Edited by mk=john, 21 December 2011 - 08:24 AM.

[Ivor Badger]

The primary gear and seal can be replaced in situ with the correct tools. I would imgine any good mini spares place sells them. But the problem is not the seal, but excess oil from the primary gear bushes. So change to the later primary gear and block the oil feed. Unfortunately, you can't get the end cover off far enough to do this in situ, so it's engine out time.

[Guess-Works.com]

Not with some transfer cases as the primary gear will not go through the hole...

Or rather, not using the tool which pulls the primary gear which thus pushes the seal out, but does not stop you picking the seal out and putting a new one in.

Those affected are transfer cases with a lip or flange that the primary gear ( or rear ) seal is pressed in up to. This flange was later deleted and you needed to use the 'special tool' to put the front seal in square.

Edited by Guess-Works.com, 21 December 2011 - 01:04 PM.

[mk=john]

if I were to jack up the rear (flywheel) side of the engine, would that give enough clearance to remove the transfer case without engine removal?