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MG Midget and Sprite Technical - 1275 ventilation for gearbox leak

MG Newbie here tackling an oil leak which I believe is now confined to the gearbox. I've gone through the multiple threads on this and would like to address this short of pulling the engine and gearbox.

I have replaced the gaskets on the oil pan, and am now led to the issue of addressing inadequate vacuum which might inhibit the return of oil from the gearbox.

I do not have a PCV, instead the engine valve cover has a vent which connects directly to the carburator (see pic). The air filter I got from the VB catalog does not quite encase the mesh leaving gaps near the vent hose.

Do you think I would see significant improvement by sealing up the gaps, or is it typical for folks with these engines to use another solution for improved vacuum?

Or is there some other easy checks I can make?

I have an MG midget MK1 / 1963-64 so it is apparant the engine was upgraded at some point in its history.

Many thanks

JD Anderson

might be best to leave it alone as it will stop it rusting away, lol
d a hadaway

Hi, JD.

The engine and transmission oil are separate, and never the twain shall meet. Under ideal conditions, anyway... they are filled and maintained separately.

So if it's truly leaking from the gearbox, nothing you do with the PCV plumbing up front will help. Where is it leaking from, precisely? If it's dripping off of the bottom of the clutch housing, it may be the rear main seal that needs some attention - that, or you actually do have a vacuum issue. The purpose of the PCV system is to draw a vacuum in the engine, thus lessening the possibility of internal engine pressure forcing oil out through the seals, etc.


Gryf Ketcherside

Gryf is spot-on, however if the spigot bearing and/or gearbox input shaft bearing are badly worn then the 'box will leak through the scroll seal inside the bellhousing and oil will drip through the little hole (with a big split pin through it) at the bottom. The gearbox breathes through the speedo cable BTW.
David Smith

The gearbox oil level is fine. It's the engine oil which I have to add 1/2 quart to after a weekend's worth of driving.

It's wiped dry now, but in the attached picture, the oil comes out of the hole in the bottom of the gearbox, travels down the ridge and drips to the ground off the engine block joint.


JD Anderson

Ah, okay. 'Tis as I suspected. It's almost got to be the rear main seal. Again though, I'd suggest double-checking your vacuum system to make sure it's drawing well. If not, putting it right may well decrease or eliminate the leakage.

Gryf Ketcherside

This thread was discussed on 10/08/2010

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