4 replies to this topic

[sebseb8]

Soon after getting my mini I changed the oil and found a chip in the edge of the sump plug hole. I thought I could fill it using a second washer hoping the washer would mould to the shape of the chip sealing the oil in. This isn't the case and it is still leaking quite a lot of oil. I don't totally understand how the oil is getting past the thread and out of this chip but I cant see where else the oil is coming from.

What is the best way of repairing the chip?

I have attempted to draw the hole with the chip, the outer ring being the edge of the hole and the inner ring being the thread.

Thanks in advance,

Seb

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•  sumpplugdrawing.jpg   6.42K   2 downloads

Edited by sebseb8, 28 October 2012 - 11:16 PM.

[Ethel]

Threads don't seal, unless they are tapered (like the oil pressure switch). You might manage to fill it with Chemical metal, or some such similar propriety repair compound.

Drilling some small holes might help it form a mechanical joint with the casing & it will need to be spotlessly clean. Making up a plate to cover the whole sealing area & bonding that on might be a good way of ensuring you're left with a flat face that will form a seal. Some PTFE plumber's tape could be handy to insert the plug without it bonding to the uncured filler.

[sebseb8]

Threads don't seal, unless they are tapered (like the oil pressure switch). You might manage to fill it with Chemical metal, or some such similar propriety repair compound.

Drilling some small holes might help it form a mechanical joint with the casing & it will need to be spotlessly clean. Making up a plate to cover the whole sealing area & bonding that on might be a good way of ensuring you're left with a flat face that will form a seal. Some PTFE plumber's tape could be handy to insert the plug without it bonding to the uncured filler.

That would explain why it still leaks.

Thanks for your reply and I will look into types of filler. I don't suppose you have any particular reccomendations or links??

Thanks,

Seb

[tiger99]

Ideally a quick bit of MIG or TIG weld, followed by retapping the hole and refacing the flat surface would have it as good as new, but that would need every trace of oil to be removed from the area, meaning a full strip down. I would try Araldite (not rapid, the slow setting grade is stronger) for filling it.

The other way is to drill the hole to a larger size, and either screw and epoxy, or weld in a top hat bush, to effectively permanently fit a new thread, or maybe just open it out and fit a larger plug. In this particular instance a helicoil is of no use.

[dklawson]

Welding and machinging while "proper" is a bit overkill for this problem. I like Ethel's suggestion to drill a small hole in the middle of the chip and filling that hole and the chip with epoxy (chemical metal). The epoxy would be left proud of the surface then carefully filed flat after it cures. The pilot hole would help anchor the fix. Remember that this repair/fill will only be under compression so it isn't going to be subject to shear loads that cause "glue" to fail. In this case, I would thoroughly degrease the area with spray brake cleaner and use JB-Weld to form the repair. I would NOT use any 5-minute epoxy products. You want the harder, stronger bond formed by epoxy that requires overnight curing.

One other change I would make is to change the type of sealing washer you use. I am a very strong proponent of using bonded metal/rubber seals (I believe Tiger calls them Dowty washers or Dowty seals). The rubber easily conforms to the surface and compensates for surface irregularities. They take a LOT less torque to seal than the copper washers. A washer for a G3/8 (BSPP) pipe should work well. If those are not available to you, visit the local parts store and see if they have similar metal/rubber washers (14mm) for drain plugs. If that is not an option, look for nylon 14mm drain plug washers. Nylon also compress well with low torque. 14mm should not fit but it is the closest size I have ever found. You will need to "thread" the 14mm washer onto the Mini's 5/8" drain plug. Once it is under the head of the plug it will work as normal.