Fuel tank drain plug bushing came loose

[Rutger-peer]

Hi there!

It's been a while since I've posted anything but just now I've ran into a problem I've not encountered before and which gives me just a slight headache:

I wanted to drain my fuel tank and therefore I wanted to unscrew the drain plug. Instead of the plug coming loose, the entire bushing that the plug screws into came off. Seems like it's pressed into the aluminium, but since it doesn't envelope the sheet metal of the tank and the fit is quite loose, I wonder whether it was originally glued tight or so.



Anyone had this problem before?

There's no flare on the sheet metal of the tank or on the bushing itself; it slides right out and in.

 

[R 4 Ash]

Interesting as im going to drain mine soon

 

[malcolm]

I've had this happen before. I don't try to unscrew the fuel drain now.

If I recall mine was brazed in. It's difficult to fix as any welding or brazing risks making the fuel tank explode. Maybe a fuel and ethanol resistant epoxy would work. JB Weld night have one

 

[Piet]

I don’t trust epoxies etc unless you can do it in a laboratory. Two ways I would do it:
People do weld or braze fuel tanks provided the tank is entirely filled with water.
Alternatively if you cannot find anyone to do that, weld or braze a large flange to the sump plug outer, then fix the flange to the tank with a goodly amount of blind tank rivets- ie pop rivets with a solid end. When you attach also “wet assemble” the flange to the tank and the rivets into their holes with a polysulphide rubber (PR) RTV compound. Both rivets and sealant can be got from aviation suppliers but there are automotive equivalents around.

 

[André4Renaults]

It's difficult to fix as any welding or brazing risks making the fuel tank explode.

As the risk of repeating myself..... Careful now!

 

[Homegrown]

Know assies empty the tank completely from fuel and the hook it up to an exhaust pipe from running engine for half an hour to an hour.
The inert warm gas will make tank safe to weld or solder after the treat.

And if you are lazy JB-weld works.

 

[Cyprusnoddycar]

I would take the tank out and check how rusty it is inside first, if it's okay make sure it is fully empty and inert. And solder the flange back in with a big washer around it to make it stronger. Or buy a new tank from De Marco in Italy !

 

[Rutger-peer]

Thanks all! I haven't figured it was brazed, but that makes sense, yes. I also noticed some soft metal around the edges, I assumed it was aluminium from the tank, but should've put 2 and 2 together. I'll empty the tank, fill it with water and wait etc etc etc, then braze the ring back in. Thanks for the tips!

 

[angel]

It's soldered, not brazed. If you have access to a soldering iron (the old style block that you heat over a flame), it's the most safe way to do it.

 

[Rutger-peer]

Hey all,

Thanks for the tips. I enptied the tank, filled it up with water a few times, then thoroughly ventilated it using pressurised air and then let it sit for a night. Then got to work and soldered the plug back in.

Some thoughts and experiences: I soldered the plug back in using a gas torch and a creme brûlée torch so I could dose the heat better. The trick with soldering iron to zinc, in this case, using a flame is to use some flux and to try not to heat the material up a much higher temperature than the melting point of the tin used. This can be done by not applying the flame directly to the spot you're trying to solder. The problem with overheating is that the flux you're adding, or that's in the soldering wire's core, will burn, thus leaving a residue that will prevent the solder from 'sticking' to the surface.

This may be tricky and the process may require several steps of adding solder onto the surface of both parts you're trying to solder together, cleaning up again and giving it another go until all surface area is covered. Only starts joining the two parts together once that's achieved. Then heat the two parts in unison.

At least, this is what I learned. If you've got a soldering iron with enough power, that's obviously the best option, since it will never overheat. Heating up bigger parts with a soldering iron may however not be possible.

Anyway, the problem is fixed. I also sealed the plug in the bushing with solder. This should not leak anytime soon.