Oil drain plugs

[V]

Can someone give me one good reason why an oil drain plug would be made to use a special 8mm square key to remove it? 
 

I am angry I can’t complete my major service on my 2.8 CRD today because I don’t have the special tool. It wasn’t mentioned in the FSM so I don’t know if it’s original or some bodge.

[Gerald F]

I found some old tools from my Series 3 Land Rover (long gone!) yesterday. One looked like just the tool you needed, though perhaps a little larger. It must be something about sump-plug designers, I suppose, but why?

Perhaps having four sides gives a bigger difference between the AF and diagonal measurements, which would allow the application of more torque before either the plug or the spanner strips and rounds out. At least the LR came bundled with the appropriate square Allen key.

[jerryg]

14 hours ago, V said:

Can someone give me one good reason why an oil drain plug would be made to use a special 8mm square key to remove it? 
 

I am angry I can’t complete my major service on my 2.8 CRD today because I don’t have the special tool. It wasn’t mentioned in the FSM so I don’t know if it’s original or some bodge.

It's probably just a ploy to dissuade owners from doing their own maintenance. I have built up a comprehensive tool kit of these more unusual tools - sump plug keys, recessed hex keys, split blade screwdrivers, 3 pointed blade screwdriver, etc etc. Always handy to have available but a pig if you haven't got one when you need it!

[V]

8 hours ago, Gerald F said:

Perhaps having four sides gives a bigger difference between the AF and diagonal measurements, which would allow the application of more torque before either the plug or the spanner strips and rounds out.

That's a reasonable theory. But why not make it 3/8" square drive so a regular socket extension would fit it?

 

The problem with drain plugs is usually over torquing them when not using a torque wrench. Aluminium sumps particularly will strip threads or crack.

[V]

23 minutes ago, jerryg said:

It's probably just a ploy to dissuade owners from doing their own maintenance. I have built up a comprehensive tool kit of these more unusual tools - sump plug keys, recessed hex keys, split blade screwdrivers, 3 pointed blade screwdriver, etc etc. Always handy to have available but a pig if you haven't got one when you need it!

I have had regular hex head drain plugs on most of my vehicles with some having hex key or Torx key plugs, but this was the first time in 43 years that I've had a drain plug that needed a special tool. I think you are right about discouraging vehicles from being owner maintained otherwise the plug would be 3/8" square drive not 8mm.

 

I did manage to change the serpentine belt, belt tensioner, both idler wheels, air filter and vacuum filter which cured all of the annoying squeaks and rattles that the engine had. It now sounds like a 2.8 CRD.

 

[digger]

I agree with V and Jerry. However its been the same for as long as I remember. 

I had an absolute sod in our Suzuki . It had been overtightened in the last dealer ''service''( that's another story!) when  still under warranty. It was a steel male square in alloy. In the end I resorted to my sump plug cure all!  I keep two sets of easy outs,one male ,one female, on the shelf! As usual iIhad to buy a new plug.

On my KJ some years ago now I had a similar issue. The sump pan thread  had been stripped during previous ownership and then the plug had been  glued back in! Good fun for me! I enlarged the hole , retapped thread and fitted a Fumoto Quick valve (a tap!) It was easy , worked well and no more trouble for rest of my ownership!

Edited September 15 by digger

[V]

10 minutes ago, digger said:

I enlarged the hole , retapped thread and fitted a Fumoto Quick valve (a tap!) It was easy , worked well and no more trouble for rest of my ownership!

You are the first person I know that has bought one. I like the idea, but I also like knowing that my sump plug is torqued correctly. I may go for one of these on the KJ.

[digger]

Well V , the thing was I couldn't buy a plug large enough to fit the resulting hole(the previous guy had done a really 'good' job of b.......g it up up)  but Fumoto offer a big range of threads which solved the issue! I torqued it in  and locktighted it . I was a bit concerned that the tap could possibly be knocked open even though it locked. None the less it was up out of the way plus I took the precaution of adding a cable tie around it to secure the lock even more. It never gave me any trouble and changing the oil was a breeze!