Dimple magnetic drain plug

Last time I rebuilt the engine in the Alpine, I was surprised at how much “glitter” was left at the bottom of my drain pan after the first few oil changes. This time around, I figured that it might be a good idea to install a magnetic drain plug and try to catch some of the ferrous swarf that collects in the oil after a fresh rebuild. My hope is that if some particles stick to the magnet, fewer are left to circulate through the oil system and cause rapid wear or other damage.

There are lots of magnetic drain plugs on the market. However, the Alpine uses an unusual 1/2″ BSP thread for the oil pan, and none of the plugs available from Moss, Victoria British, or any of the other usual suspects will fit. (The only other car I know of with the same thread is the MG TC.)

Enter Dimple. Dimple makes magnetic drain plugs for a wide variety of threads and applications.

While there isn’t a 1/2″ BSP plug listed on their website, I e-mailed them and one is available. I ordered one and it arrived a few weeks ago. The plug has a very strong magnet permanently mounted in the center of the plug. It’s so strong, in fact, that it can be challenging to install the plug because it wants to pull to one side and stick to the drain pan instead!

Left: Ordinary drain plug Right: Dimple magnetic drain plug

One other quirk is that the head of the plug is a 17mm hex, meaning that a metric socket is required to install it. I try to keep metric tools away from the Sunbeam, but unfortunately an 11/16″ socket is a very loose fit. Why is the head metric, while the threads are English? I suspect that Dimple does this to simplify production – they probably machine the same 17mm hex on all of their plug “blanks” first, and then machine the threaded portion as needed for many different applications. It would be nice if they used a standard size hex so that I don’t have to carry a metric socket in my car just for the drain plug!

The plug comes with a Dowty-style rubber bonded sealing washer installed, which should help prevent leaks.

The Dimple magnetic drain plug costs about $40 shipped within the US.  That’s not cheap, but it feels like cheap insurance compared to the cost of a rebuild.

As I mentioned, the 1/2″ BSP plug is not available on their website, so you’ll have to send an email to info@drainplugmagnets.com to place an order. Ask for a 1/2″ BSP plug (part number SPL 1/2″ BSPP).