Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 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!

Thanks Andy - this will come in very handy as like you say its easy to strip the sump plug thread.....

Superb thread Andy, I hope I dont go there but at least I now know how to get out if I do !

Good result Andy despite a longer than anticipated journey

The M14 x 1.5mm oversize plug you recommend with hindsight should work fine but beware that the tapping drill size for this is 12.7mm which is exactly the major diameter of OE thread so check extra material hasn't been torn out when OE thread stripped.

Thanks for the detailed information Andy, it will save us all the same trouble you had if it happens. I would certainly have gone for the helicoil first as well, I hadn't considered the seal seat chamfer until you mentioned it. Now you just need to find a good place to wire lock it to.....

Has anyone found a torque spec for the original drain plug, or a recommended torque for the new modified plug?

Why are you removing the sump plug from a dry-sump engine?

Because it's not as "dry" as it should be, particularly after a long lay up. You can either try and scavenge the excess oil in the sump back to the tank on start up, hopefully without it all ending up down the front of the engine, or drain it out before starting and put it back in the tank. The other hazard of starting the engine with all (or most of) the oil in the sump and a pair of big pistons thrashing up and down is hydraulicing and blowing the engine seals. Some X-Wedge engines do not drain the oil tank into the sump, mine is pretty good fortunately, but others are not good in this way.

Mine doesn't accumulate much oil at all in the sump, even over a winter layup. I suspect those who have issues with oil accumulation in the sump may have abnormally high clearances in their oil pumps.

I think you are probably right Bitsobrits. The oil light will still go out and the pressure will be within limits, if you have a gauge to see what the pressure really is. I doubt it's worth the cost and effort to chase the solution. Probably the clearances are not "abnormally" high, just on the high side as many seem to suffer this issue and mileage seems not to be a factor. We are lucky this isn't a problem on our engines 😊 but I have a very noisy bevel box ☹️.