[Transmission] 2005 1.6 HDi Gearbox(?) leak

[davidc]

Can anyone help with the following, please?
I have an oil leak which I assume is from the gearbox. On the attached photograph it can be seen on the aluminium(?) casting against the light area in the background (it's a caravan). It seems to be coming from near the gearbox drain plug and running to form the drip. I don't think it's from the drain plug as there is no sign of it and there is a gap between the plug and the casting. 
If I clean it up it does not reappear overnight. However, when I take the car for a short run it's there again immediately.  I've tried to find diagrams etc to tell me what the casting is without success. It appears to be attached to the gearbox with fixings through two hexagonal "tubes". I've tried nipping these up but it made no difference. Any advice gratefully received !!

[cancunia]

Can you post some more pictures of the gearbox?
Maybe this will also give you a clue....
http://www.catcar.info/citroen/?lang=en&l=

[davidc]

Can you post some more pictures of the gearbox?
Maybe this will also give you a clue....
http://www.catcar.info/citroen/?lang=en&l=

Thanks for taking the trouble to respond.
I've attached another couple of photographs. One is from the front and shows the casting in relation to the gearbox and surrounding area. The other is from the other side and shows the nuts I mentioned in my original post that I nipped up.
I'd come across the site you referenced in my previous searches. Unfortunately I can't see anything on the various exploded diagrams that look similar. I guess I'm wondering whether there are some seals as part of, or above, the casting (whatever it is) that could be leaking ??
Thanks again.

[davidc]

Can you post some more pictures of the gearbox?
Maybe this will also give you a clue....
http://www.catcar.info/citroen/?lang=en&l=

Sorry, first attachment missed.

[cancunia]

Apologies, it's been a while since I had my 1.6 M59. It looks like the casting is at the back of the gearbox? It may be that the oil is coming from above, there are a couple of suspects that come to mind:

1, The EGR valve - check that it's tight, you'll need the battery out for that.
2, The airbox - maybe the breather pipe from the rocker cover is loose.

[davidc]

Apologies, it's been a while since I had my 1.6 M59. It looks like the casting is at the back of the gearbox? It may be that the oil is coming from above, there are a couple of suspects that come to mind:

1, The EGR valve - check that it's tight, you'll need the battery out for that.
2, The airbox - maybe the breather pipe from the rocker cover is loose.

Yes, the casting is at the back of the gearbox, (just behind the drain plug), but attached to it.
Thanks for the suggestions. I'll check them out.

[oilyrag]

Had a quick look at second-hand gearbox images and found one with the same casting - might it be a bracing for the differential casing? - only appears occasionally and looks a bit of an afterthought! There is a part number on your picture but I can only see part of it. Maybe the whole number will help.    

Looking at the 4 attachment nuts the casting appears to be 'solid' and there are no oil ways into it. Any leaks that are coming from the mounting studs could probably be sealed with RTV sealant. Try putting a sheet of clean kitchen paper above the casting and see if the oil is actually coming from a 'higher' source, as mentioned above.  Gearbox oil has a characteristic 'cat's pee' smell!

[cancunia]

Try putting a sheet of clean kitchen paper above the casting and see if the oil is actually coming from a 'higher' source, as mentioned above.  Gearbox oil has a characteristic 'cat's pee' smell!

Good point, the engine oil will also probably be a lot darker than gearbox oil.

[davidc]

Had a quick look at second-hand gearbox images and found one with the same casting - might it be a bracing for the differential casing? - only appears occasionally and looks a bit of an afterthought! There is a part number on your picture but I can only see part of it. Maybe the whole number will help.

Looking at the 4 attachment nuts the casting appears to be 'solid' and there are no oil ways into it. Any leaks that are coming from the mounting studs could probably be sealed with RTV sealant. Try putting a sheet of clean kitchen paper above the casting and see if the oil is actually coming from a 'higher' source, as mentioned above.  Gearbox oil has a characteristic 'cat's pee' smell!

Thanks for taking the trouble to look at this.
Despite poking around there I'd missed the part number (what an idiot).  The full number is 9644715380 and it is just a gearbox mount so you're right about no oil ways into it. I'm pretty sure it is gearbox oil as (to echo cancunia's point) it look too light to be engine oil. I've had a good look around already but I think I'll just have to start stripping bits out to get a better look. As I mentioned, it only leaks after the car has been driving so I'll take it for a run before doing so and see if I can spot any fresh trails.
Thanks again.

[oilyrag]

Given the proximity of the driveshaft to the casting in question it might be a leak from the driveshaft oil seal. The  'mount' is odd as it doesn't seem to actually mount to anything in particular!  Pic shows the seal position. (Red), Yellow shows mount position.