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MG Midget and Sprite Technical - Changing diff oil

Hello all. I am changing the diff oil.

I have tried and failed to move the drain plug. it seems to be jammed solid

I am using a drapper mutii key on this under the car supported by wooden sleepers.

I'd try heat but not sure how safe this would be so close to the tank.

Any ideas would be most welcome.

Is there a specific tool someone can suggest?

Gavin.

Gavin Rowles

The problem is that with the oil still in it, any heat will have to warm that up before anything happens. I'd suggest warming the diff with a heat gun and siphoning out the oil when it's thinner. Then carry on with the heat gun and keep trying. You will not get it very hot, but it's surprising how much effect even a bit of heat can have. Does your key fit really well into the square socket? If so you can get a long bar onto it. I use the handle from my old trolley jack. If you are worried then drain the tank, but the vapour could still cause an explosion with a naked flame, hence the heat gun used carefully.
Les Rose

if you're using the Draper multi-headed tool you wont get an extension bar or tube on it. if the plug is a half inch square then use a ratchet which has a round section handle. Gently hammer the square drive into the plug, fit a suitable metal tube over the end (Les' jack handle is a good example) and a good heave should free it.
David Smith

A ratchet with 3/8 drive direct (no socket) is the best I have found. Or, once, I resorted to a pair of stil1sons on a particularly reluctant drain plug.
Rob
MG Moneypit

Gavin, you do know to check you can remove the filler plug before draining?
GuyW

Thanks all I will try using the small home heater I have first and if required buy a heat gun. I'll try the 3/8 ratchet idea too.

Also remove filler plug first.

The drain plug is not in great shape due I think to previous owners & my attempts!

Gavin.
Gavin Rowles

Replacements are cheap (£2 to £3) and now feature a hex head for a big allen key.
Rob
MG Moneypit

Gavin, if you're going to replace the bung give it a good wack on the end with a decent sized hammer and that'll loosen it up in the thread--maybe someone has given it a dose of sealant that stuck it there and a friendly whack 'might' break it's grip
willy
William Revit

Gavin,
the Draper multitool is pretty near useless and using it on a plug that is already damaged may damage the plug more. I found cutting the tip down on the Draper tool help it sit lower but I can't remember now if that removed the plug.

Don't try any further until you have two new replacements and have checked you can fully remove the fill plug as Guy has put.

Once you know you can fully remove the filler plug and will be able to remove the drain plug then don't, go for a ride to get the diff oil as warm as possible and then remove the filler plug first then the drain plug and let the existing oil drain for as long as possible.

I have some warmed new fresh oil to tip in at the end of the drain to act as a final mini flush but as the axle takes about a litre you can't do this if you only have one litre of fresh new oil.

If you let the oil drain into a clear container you can check it and compare it against your fresh oil.

Don't overfill as it's a waste, better to slightly underfill and top up whilst under there it'd be a good time to clean and check the axle vent is clear.

Good luck, I got my cracked plug out with just the simple tools (no heat) and with time and patience but the last two are often out of stock with many. I try not to start any job on the car without plenty of stock of both but patience is a lot more difficult to hold on to with cars for me.

Nigel Atkins


All sorted now with some extra grunt. I'm too mean to get a new hex key.

I will check the vent though. Thanks all.
Gavin Rowles

Well done.

But I hope you're not too mean to replace at least one plug if not two. The number of jobs on the midget where I didn't bother replacing a part or doing something to make the work easier next time thinking it doesn't matter I won't be doing that again, and I have, especially where new parts have been fitted. Learn by my mistakes.
Nigel Atkins

This thread was discussed between 26/02/2022 and 06/03/2022

MG Midget and Sprite Technical index

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