RS Rider wrote:Have you tried MotorWorks?

https://www.motorworks.co.uk/catalogsearch/result/?q=61311459047&find=k-series-k100-k100rs--09-1984---08-1988--121

daveyson wrote:If you can't see a crack or failure, there's a good chance your pump (edit, gauge, haven't had my coffee yet) is good. There's a few ducks that need to line up before installing this earlier type. There's a thread on this topic but I don't remember the name of it.

One of the problems in that case was that the pump edit gauge) was not installed at 90 degrees to its base, but was very slightly out.

daveyson wrote:So parts are slowly coming back to me.

If this leak started after the gauge has been removed and replaced, then there might be something wrong with the installation.

I think in that case the seal was going in parallel to the threads so it bottomed out crooked, and wasn't fully seated, so then the nut wasn't fully home. Check if all the threads are engaged, maybe even post a photo.

I think he ran out of patience and sealed it up with epoxy, you don't want to do that. Also there was a problem with connecting the electrical plug, irrelevant for this thread.

daveyson wrote:I found the thread, dunno how to do links, it's at the motobrick forum. It's called 1985 K100 fuel leak at sending unit - replaced the rubber gasket and it still leaks.

daveyson wrote:Yep we're talking about the same unit.
I found the thread, dunno how to do links, it's at the motobrick forum. It's called 1985 K100 fuel leak at sending unit - replaced the rubber gasket and it still leaks. I typed in something like BMW K100 fuel leak under tank daveson site:motobrick.com and it popped up.

You wouldn't think that a topic like this would go for three pages, but it did. Hopefully the answer might be there, or another thread, there's so many.

Laitch wrote:

daveyson wrote:I found the thread, dunno how to do links, it's at the motobrick forum. It's called 1985 K100 fuel leak at sending unit - replaced the rubber gasket and it still leaks.

This looks like it.

Point-Seven-five wrote:My money is on a crack under the nut where the connector shell joins the sender body.  The crack could be caused by an impact on the connector when the cable is attached. 



The screwdriver is pointing at where I suspect the crack is located.  That top flange that retains the nut hides the crack from view.  If it were my sender, I would cut that flange off and remove the nut.  That will permit the part to be inspected and if there is indeed a crack will allow it to be repaired.

Removing that flange will also allow the sender to be offered up to the tank so you can see how the gasket is sealing and if the sender is being cocked to the side as it is inserted.

If there is a crack, I would repair it by opening it up and putting some JB weld in the opening.

Point-Seven-five wrote:Is this the part you are having trouble with?

https://www.motorworks.co.uk/fuel-level-sender-tak59047-1.html

Does it function properly as far as sending fuel level information? 

You seem to indicate that it is leaking.  Is that the only problem?  Have you inspected it closely for cracks or damage?  I have never owned a bike with that sender, but I have heard that they are somewhat fragile.  BMW hasn't stocked them for a while now which will make finding a new one a bit difficult.

If it isn't leaking past the gasket, and it isn't cracked, the leak may be around where the electrical connectors pass through the molded body.  It may be possible to repair, but it would depend on where and how bad the leak is, and so far you haven't been able to tell us much about it.

daveyson wrote:When pressed against the inner flange, does the nut spin smoothly when turned, with the gasket removed?

It might be worth blowing compressed air through both sides in case there is some grit preventing a good seal.

I think now that the motobrick thread I referred to is a red herring. It's a safe bet that when assembling this unit, the nut was placed on the sender and then the electrical plug was pressed on. If the plug isn't exactly parallel to the sender, so what. It doesn't matter if the nut isn't parallel with the plug. But on second thoughts, I think his solution is worth considering, and he solved his leaking problem. It would at least get you going again, so you're not under time pressure, in case you still want to look for a replacement.