Engine drain plug troubles


This past week I went to change the oil on my '88 F75 2.8TD, unfortunately after the plug was back on, the vehicle was dripping by the drain plug like crazy.

It seems someone (previous owner?) when changing the oil last time didn't have it screwed in correctly and the threads in the oil pan are ruined...

The solution the mechanic offered seems sensible - and basically involves using a thread insert kit with the differential filler plug size (larger thread than original) on the oil pan - and fitting a differential level plug instead of the engine drain plug.

Now, my questions are:

Is the engine oil drain plug fitted with a magnet? If it is the differential filler plug has no magnet, only the differential drain plug.

Should I apply a gasket/washer on the new engine oil drain plug, which is going to be a differential level plug?

What are the dimensions and material of this washer/gasket? The one I have here seems to be made of some kind of metal (aluminium?) and the dimensions I measured are:

Thickness: 1.2 mm
Inner Diameter: 17.5 mm
Outer Diameter: 25.5 mm

The differential filler plug size/thread is M18X2.5.

Before all this, FWIW I'd be

Before all this, FWIW I'd be looking for a replacement sump pan with plug from a breakers. It'd be cheaper and less hassle in the long term. If he's going to make a proper job of this insert/helicoil the sump will have to come off anyway.

As regards the plug, well these days they tend to have magnetic properties as opposed to having a seperate magnet fitted. Check this on your original plug.You can always magnetise the replacement yourself if you feel you need to but IMHO it's a bit of a gimmick. And for the washer, well a good copper one has always served me well. Take the replacement plug to an engineers supplier or fastenings specialist and they will match you one from stock. HTH.

Dave with a Sporty

Dave with a Sporty

when it comes to getting a

when it comes to getting a new plug, get a difflock one, they dont have to be undone again as they have a tap and drain hose, best mod you can do at the price

Plumbers tape.

Have you tried wrapping 'gas tape' around the old plug thread and then screwing it in? [plumbers white tape ... comes on a roll about 1cm wide and very thin]

You are not the only one....

Exactly the same thing has happened to me - someone has damaged the thread of the sump plug on my 1985 Rocky.

I've tried using copper sealing washers and PTFE tape to no avail, but I found that a thick rubber washer (abut 5mm thick) does the trick. When the plug is done up tight the rubber washer is very squished (down to about 1 or 2mm), and so I use a new one each time I change the oil.

In the long term, I intend to get a 2nd hand sump pan from somewhere, although my fix does appear to be leak tight at the moment.

I also noticed that the pan is dented around the hole - like someone has damaged that whilst tighting / trying to loosen the plug.

I don't think the that the sump plug is magnetic.

1985 Veg oil burning Fourtrak "Rocky".

1985 Veg oil burning Fourtrak "Rocky".


Some sump plugs are fitted with a magnet bonded into the middle, others are simply magnetised steel, while some are just plain sump bungs with no magnetism.

Magnetic bungs seem to be fitted for vehicles destined for poorer countries with poor quality lubricants not freely available, not really a problem with European models.

Ditto the comment above

Ditto the comment above about the Difflock sump plug, that's what I am going to do next oil change. I think the problem with the Fourtrak sump is that the threaded "nut" part is welded into the much thinner steel of the sump by a process that leaves 3 small dimples in the steel right on the flat face where the washer has to seal. This means that whatever washer is used has to deform quite considerably to fill the dimples. This leads to people overtightening the plug in order to seal a re-used washer which, over many oil changes, damages the threads in the sump. The genuine sump plug washers are steel with a fibre layer bonded to one side which don't deform anywhere near enough. I bought 10 of Milner's all fibre washers and use these two at a time to get a seal on the plug, although as said above, the Difflock plug would be a much better solution so long as you can actually get a leakproof seal when fitting it.

Regards to all - Alastair.


There is not sufficient thickness to successfully insert a helicoil into the sump plug socket, and these are screwed in anyway, so another source of leaks.

There are two successful options to repair this, one is to use what is called a bonded seal, this is for hydraulid connections, and is soft metal with a neoprene coating on either side, this deforms when tightened.

Option two is to remove the sump and drill out the existing plug socket, turn another one on a lathe, and make it much thicket to allow it to be mig welded in without deforming. This will have a nice flat face and can be tapped with any thread to suit any bung size you require.

I'm still trying to solve

I'm still trying to solve this problem - anyone knows how much a new oil pan might cost?