MS2 gearbox oil leak

[Freda class]

I have a steady but slight oil leak from behind the two hex headed studs that hold the cooling manifold onto the MS2 gearbox.
I've tried fibre washers, copper washers and even a combination of the two but no success.
Any help much appreciated.

 

[VicS]

Are you sure the leak is actually from the two bolts, not running there from higher up?

 

[Freda class]

Yes, absolutely sure. I've cleaned all the oil off and re-photographed it several times and the area above the bolts is always clean.
The only other possible source is from the smaller hex bolt above and between the two larger bolt heads but that is always dry.

 

[VicS]

Yes, absolutely sure. I've cleaned all the oil off and re-photographed it several times and the area above the bolts is always clean.
The only other possible source is from the smaller hex bolt above and between the two larger bolt heads but that is always dry.

It seems strange that the oil is only leaking from under the heads of the bolts and not from between the cooling manifold and the rear of the gearbox or from the joint with the main part of the gearbox.

If you are certain about the leak why not put some sealant or some silicone instant gasket on the bolt heads.
I assume if you take either of the bolts out oil runs out of its hole from the gearbox so you have to drain it to try anything.

 

[Freda class]

The curious thing is that there isn't a rush of oil when I remove the bolts which leads me to believe that they are blind bolts.
I'll try the instant gasket though and see if that's a fix.
Thanks for your thoughts.

 

[VicS]

The curious thing is that there isn't a rush of oil when I remove the bolts which leads me to believe that they are blind bolts.

Then I'd look again at the possibility that it's the output shaft seal that is leaking and that oil is running down from that.

It will be difficult to see clean oil so maybe it's possible to clean up thoroughly and then put a tissue or piece of paper kitchen towel on top of the manifold.

 

[Freda class]

OK I'll give that a go. Thanks again for your thoughts.

 

[Steve_N]

I'm not that familiar with the MS2 but looking at the exploded diagram on marinepartseurope the manifold connection is similar to that on my MS3 which I recently had in pieces.
If that is the case then a water pipe protrudes loosely through the gearbox casing and into the manifold. An O-ring is slipped over this pipe and is compressed in an angled seat as the manifold is tightened against the casing. This seals both the water pipe into the casing (keeping oil in the casing) and the water pipe into the manifold (keeping water in the pipe and manifold).
If you have an oil leak from this point then you may also have water and oil mixing together so I'd suggest removing the manifold and replacing the O-rings is required.

 

[Freda class]

Steve_N,
So far no sign of any water emulsion in the oil so the traffic seems to be one way!
Everything cleaned up again today and I'll have another look tomorrow but the leak is there whether the engine/ gearbox has been run or not.