Series MM oil leak

Discuss mechanical problems here.

Moderator: Moderators

indianmorrie
Newbie
Posts: 2
Joined: Thu Mar 16, 2006 5:05 am
MMOC Member: No

Series MM oil leak

Postby indianmorrie » Thu Mar 16, 2006 5:11 am

I have a '49 MM convertible with an original engine (918cc Sidevalve). It runs fine even at low speeds but it gives out about a litre of oil every half an hour when its running. the oil comes out through a small hole below the flywheel.

Ive replaced the oil seal, changed the main bearing, and even used thicker engine oil but it just doesnt stop!!!

How do i stop it??!!

Johnno
Minor Fan
Posts: 204
Joined: Wed Apr 28, 2004 8:33 am
MMOC Member: No

Postby Johnno » Thu Mar 16, 2006 8:27 pm

Hiya,sounds like the rear main oil seal to me but if you have replaced that correctly then I suggest you look for a crack in the alloy sump.All the best, john.
Power to your Pistons,Johnnydoome.

bmcecosse
Minor Maniac
Posts: 46561
Joined: Wed Feb 16, 2005 11:24 pm
MMOC Member: No

Postby bmcecosse » Thu Mar 16, 2006 8:30 pm

Maybe the main bearings are badly worn - and the oil seal just can't hold it ? Other possibility is oil level far too high - have you definitely got the right dipstick ? You could drain off and refill with exact amount specified for the engine. Could also be high pressure in the crank-case (not oil pressure) - causing oil to be 'blown' through the seal. This would come from badly worn rings/hole in piston - and would be obvious from fume blowing out of the breather !
ImageImage
Image

Scott
Minor Addict
Posts: 574
Joined: Thu Apr 15, 2004 4:04 am
MMOC Member: No

Postby Scott » Thu Mar 16, 2006 11:33 pm

There's no rear main oil seal fitted. The only seal is between the sump & bearing cap.
There's a reverse scroll as part of the crankshaft that's designed to "wind" excess oil that comes through the bearing shells back into the sump.
When the bearings wear & have more clearance than they should have, extra oil gets past them & the crank scroll can't cope - as a result, the oil gets out & you get your leak.
If the bearings have been really worn at some stage, the actual scroll could also have been worn away from contact. In this case, the crank is scrap.

I've done a lot of work on mine & have fitted a rear main seal.
I've machined the scroll away, had the bearing cap & upper "eyebrow(?)"machined & fitted a graphite impregnated rope seal.
I've extended the oil thrower on the crank so it leaves very little room for the oil to get past before it hits the seal.
I also drilled an additional drain hole in the bearing cap to ensure that the oil can get away quickly.
This was done over the period of a couple of years. Pulling the motor out, trying different things, putting it back in........
I even cut down a sump so I could inspect the rear main area with the engine running to see what was leaking where.

All I have to do now is fix the leak at the front of the gearbox which I'll tackle soon. I have the parts ready to go, just have to pull my finger out :wink: .
Scott

[url=http://img133.imageshack.us/img133/523/bo16vy.jpg]1948 Series MM[/url]
[url=http://img133.imageshack.us/img133/2484/dcp001046qp.jpg]1962 1000[/url]
[url=http://img207.imageshack.us/img207/9625/19705bp.jpg]1970 1000[/url]
[url=http://img137.imageshack.us/img137/7259/nullabor25ns.jpg]1959 Van[/url]

[url=http://www.morrisdownunder.com/forum/index.php]Aussie Forum[/url]

bmcecosse
Minor Maniac
Posts: 46561
Joined: Wed Feb 16, 2005 11:24 pm
MMOC Member: No

Postby bmcecosse » Fri Mar 17, 2006 9:44 pm

Wow - comprehensive explanation! And sounds like lots of work.
ImageImage
Image


Who is online

Users browsing this forum: No registered users and 7 guests