Talk Morgan Forums Thread Like Summary - X-Wedge Sump Plug Thread Stripped

I mentioned in another THREAD that I’ve managed to strip the thread in my crankcase that accepts the sump plug.

While I accept full responsibility for this, there really isn’t much depth to the thread here and I guess I’m not the first and won't be the last to strip it.

Therefore, I thought it worth me passing on my experiences of how I’ve repaired it and more importantly, how I should have repaired it!.

My first idea was to fit a helicoil so I purchased the appropriate 1/2in x 20 helicoil kit.

The supplied helicoils were around twice as long as necessary so I cut one down to around ¼” long. Then I drilled out the stripped thread to 13mm and threaded it with the supplied tap. So far so good but when I inserted the helicoil the lowest coil didn’t sit correctly. Difficult to explain this, but I think it might have been something to do with the chamfer around the lower thread designed to accommodate the sump plug o-ring? Anyway, for whatever reason it was clear that it wasn’t going to work.

Therefore, I was left with little option but to fit an oversized sump plug. I used a M15x1.5 oil sump repair kit (Laser 5227) to cut an oversized thread and used one of the kit’s M15 sump plugs. [Note - ideally I would have used a M14 kit but I needed to use the M15 one because I had already oversized the hole for the helicoil misadventure.]


I found an 11mm ring spanner was ideal for turning the tap while cutting the thread through the crankcase. Obviously it was important to ensure that the tap was perpendicular to the crankcase and I took it very slow with plenty of backing up.

By chance, the copper sealing washers supplied with the Laser kit are a very good fit into the recess around the sump hole.


The sump plug head is 19mm so I will need be careful not to overtighten it! So far, I haven’t been able to find a M15 sump plug that incorporates a magnet but I will keep looking. In time I plan to lockwire it too.

With the benefit of hindsight, I would recommend doing the following if you should strip your sump plug thread.
Drill out the hole to ½ Inch (12.7mm)
Use M14x1.5 tap to cut a new thread.
Purchase one of the many available M14x1.5 sump plugs on eBay. These are cheap and often include a magnet.

...or if you want to push the boat out...

More importantly, everyone needs to be aware that the standard sump plug is very unlikely to come loose and only needs to be nipped up!

Possibly a small amount of high temp silicone sealant on the adaptor threads on assembly if it is leaking from there, or a Viton O ring under the adaptor, as with the original plug? Don't over tighten it or you will be in danger of pulling the alloy case threads again.

As for wire locking, I would lock the adaptor to the oil pressure switch by drilling a hole across two flats, then that will stay locked and not require disturbing when removing the drain plug. Finally lock the drain plug to the adaptor, always "pulling' in a tightening direction.

The great thing of our M3W is experimenting.

Personally I think one of the best solutions is using a Stahlbus oil-drain as described in our bevel box project Stahlbus-drain-on-recon-bevelbox
You have them in several thread sizes so making a new bolt-thread or a coil is perfect, because it will be the last time you ever use this bolt-thread.

To protect this and the rest I made a stone guard Stone guard

see picture