Leak (oil?) near fuel tank

Gonna find an Indy tomorrow for a look, but spotted a damp area on what I'm guessing is the fuel tank (black bit, not my car). Couldn't see an obvious route it had tracked from.

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Pretty sure it's oil but seems pretty far from the diff? I didn't sniff it but I think it would have been obvious if it were fuel.

Any thoughts?
 
Front diff seal or prop shaft u/j as it connects to the diff if it is grease like

Brake fluid would be more oil like

There is no other fluid of grease in the area other than petrol and that would evaporate that I can think of
 
IMG_20200601_122530.jpgIMG_20200601_122516.jpg

Had a look this morning and it's defo oil, though quite sticky so been there a while I'd say. And location wise corresponds with the input to the diff. In history 2 years ago, invoice for service says 'topped up diff oil' so maybe from a previous leak, or it's still leaking. No drips on the driveway.

I'll get the seals looked at I think.
 
Change the diff oil and monitor then over the winter have the diff out and serviced would be my suggestion.
 
PDJ said:
Change the diff oil and monitor then over the winter have the diff out and serviced would be my suggestion.

Any recommendation in Manchester/north west for that? Darren Wood being the obvious choice first.
 
If you have a second car and can live with out it for a few days JC Racing in Thirsk North Yorks is the place to take it

John Cockburn 07812 202553

If it has done more than 80,000 miles it is due a service if you are lucky it will be just the easy bearings and seals if it is worn John will sort it out but there is a bit that needs to be spark eroded as BMW never intended it to be serviceable.
 
I have the same on my car but only a small amount, I was thinking diff seals I had the same on my old m5. I will addressed at the next service.
Let us know how you get on
 
Matt.13 said:
I have the same on my car but only a small amount, I was thinking diff seals I had the same on my old m5. I will addressed at the next service.
Let us know how you get on

Getting it looked at on Friday and new oil ordered, so will report back.

106k miles but no dodgy noises so hopefully can factor in the diff rebuild after the rod bearings and vanos refurb :lol:

I keep telling myself all this maintenance is cheaper than depreciation :?
 
No doubt teaching you to suck eggs, but worth ensuring whoever looks at it cleans off all the old stuff, so you can see if it continues to leak.
May sound daft, but time is money, and some places wouldn't bother.
 
enuff_zed said:
No doubt teaching you to suck eggs, but worth ensuring whoever looks at it cleans off all the old stuff, so you can see if it continues to leak.
May sound daft, but time is money, and some places wouldn't bother.

I'm getting the new car new garage anxiety already :lol: local BMW and Porsche specialist so hopefully all good but yeah will make sure I ask.
 
Diff seals on these are notorious for showing signs of "weeping" , i would only be concerned if you start seeing drops on garage floor or driveway from that area .
 
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