Rounded hex differential plugs

Matt1986 · June 4, 2017

Hi all. I attempted to change the difference oil in my mk4 ls400 yesterday but immediately ran into an issue. Both the fill and drain plugs (10mm hex ) are rounded off and quite rusted in.

Anyone else had this? What can I do to remove them? I'll get new plugs to replace the ones in now.

Thanks as always. Matt

ambermarine · June 4, 2017

Matthew

Using a dremel cutter blade cut a slot in the plug and use an impact driver to shock it out .

It won't do any harm to soak both plugs for a couple of days in wd40 ,but the cut a slot impact driver works most times,be sure to use the impact type slot bit, an ordinary one will snap.

steve2006 · June 4, 2017

Just make sure you remove the refill plug first as the last thing you want is to remove the drain plug successfully, drain all the old oil and then find the refill plug is completely stuck despite all the efforts to remove it leaving you with a drained differential and no means of refilling it.

In other words make sure you can refill before draining!

As Phil mentions WD40 is also a good move as is getting the casing warm with a good drive before re-attempting the plug removals.

Part numbers are

Drain plug 90341-18035

Filler Plug 90341-18032

Gaskets for both plugs 12157-10010.

Expect to pay around £12.00 for the lot.

Matt1986 · June 4, 2017

2 hours ago, ambermarine said:

Matthew

Using a dremel cutter blade cut a slot in the plug and use an impact driver to shock it out .

It won't do any harm to soak both plugs for a couple of days in wd40 ,but the cut a slot impact driver works most times,be sure to use the impact type slot bit, an ordinary one will snap.

I have an impact driver but it only has screwdriver type bits. Is that what you mean? I tried using a chisel and hammer but it was just cutting into the plug edge.

cornershop · June 4, 2017

Is there any of the bolt head to grab? Or are they recessed? I've used Irwin bolt extractors before, big money savers in some situations. They work on round heads too.

Matt1986 · June 4, 2017

It's this type of thing.

ambermarine · June 4, 2017

39 minutes ago, Matt1986 said:

I have an impact driver but it only has screwdriver type bits. Is that what you mean? I tried using a chisel and hammer but it was just cutting into the plug edge.

Yes it is a normal straight edge, not philips etc ,You need to cut quite deep to get decent keying,and to keep the driver central to the nut.

mikeyv · June 4, 2017

The last one I had like this, I used an angle grinder, to carefully make a slot, then used a chisel, as close to parallel to the face of the plug as possible, and a hammer to shock it free.

Obviously, do as Steve says first, and make sure the filler plug is free.

cornershop · June 5, 2017

Can you tap a torx bit into there?

Matt1986 · June 6, 2017

16 hours ago, cornershop said:

Can you tap a torx bit into there?

I have heard of people doing this but I Don't have bit big enough. I'm just going to leave this to the pros I think before I completely mangle it!

Colin M · June 9, 2017

I have the same problem as you, Matt, on both my LS400s.

The approach I am thinking of is this. Get a piece of hexagonal bar (about one inch long) which is the same size as the internal hexagonal in the filler and drain plugs, clean up the rusty plug and then have the hexagonal bar welded to the plug. A socket can then be used on the hexagonal bar to (hopefully) remove the plug.

I have got as far as buying replacement plugs and a hexagonal bar from which I have cut 4 one inch pieces. I just need to get them welded in and see whether this will work.

Has anyone tried this before?

Matt1986 · June 10, 2017

10 hours ago, Colin M said:

I have the same problem as you, Matt, on both my LS400s.

The approach I am thinking of is this. Get a piece of hexagonal bar (about one inch long) which is the same size as the internal hexagonal in the filler and drain plugs, clean up the rusty plug and then have the hexagonal bar welded to the plug. A socket can then be used on the hexagonal bar to (hopefully) remove the plug.

I have got as far as buying replacement plugs and a hexagonal bar from which I have cut 4 one inch pieces. I just need to get them welded in and see whether this will work.

Has anyone tried this before?

I'd be interested to see how this works out for you. Where did you get the bar.?

Colin M · June 10, 2017

I got the bar from a steel stockholder, Edwards Metals in Witton, Birmingham.

steve2006 · June 10, 2017

I did mine a few years ago and I think preparation is the key. The plugs obviously rust and this makes it difficult to ensure the hex key has been pushed fully in, if it is not fully inserted that is when the rounding off can happen.

Regarding buying a piece of hex bar and welding it to the plug please ensure it is of high quality otherwise you may shear it off or twist it during the attempted removal leaving you in a far worse situation.

runsgrateasanut · June 12, 2017

As Steve says cleaning the hole thoroughly first is essential.

Would not an Alan key welded into the hole be ideal and it even leves you with a tail to clout with a hammer.? Then either cut off the surplus leaving a part that a socket can fit on to.. Or is the steel wrong for welding?