MG4 Reduction Gearbox Oil Leak

[Macadoodle]

Is possible but still there are cars leaking transmission fluid despite this lower level. For those cars there must be another cause.

I think you're correct.

My 1.5 meter tube with the aluminium chamber on the end looked promising at first, checked it after around 110 miles including some 4 lane 80mph blasts and .......... it was leaking like hell

The full length of tubing had trapped oil in the low spots, the chamber had overflowed, the foam I had fixed to the end was saturated in oil.
Drained the box and there was 700ml left in there, I had filled to around 850ml.

This gearbox seems to act like an oil pump in action, the alloy chamber is situated just under the rear hatch inside the bumper, so much higher than the top of the box, and it still managed to fill that fuel filter housing and push through the foam, dumping 150ml of oil. Unbelievable. No wonder MG's silly little revised breather doesn't work !

Sooo, today I threw the last dice. Blanked off the factory breather hole and fitted an adapter in the fill hole in the side of the box, well above the left CV joint.
Fitted the same hose on that after I cleaned it of oil and filled the box with 850ml yet again ( I now probably have the freshest gear oil in the country )

I've only done around 50 miles so far but I think I might be on to something. There's NO oil in the pipe so far, it doesn't seem able to push it up the initial few inches towards the underside of the boot floor far less up behind the back bumper.
Maybe I've actually lanced the boil at last and the pressure is gone ?
Will see how she blows over the weekend

 

[Hagen]

Good luck Macadoodle!

 

[Hagen]

Model year. I believe when something important changes, a transmission box by example, some start digits in the VIN code must also change. In 2022 pos.10 is 'N'.
An example of a Mitsubishi:

It should be interesting to compare the VINcode from a car with fluid leak and model year N, with a car that haven't the leak. When mg have changed the gearbox, there must be a change in the start digits I guess?

 

[Macadoodle]

Good luck Macadoodle!

Thanks. I'll probably need it

 

[Deleted member 10041]

I think you're correct.

My 1.5 meter tube with the aluminium chamber on the end looked promising at first, checked it after around 110 miles including some 4 lane 80mph blasts and .......... it was leaking like hell

The full length of tubing had trapped oil in the low spots, the chamber had overflowed, the foam I had fixed to the end was saturated in oil.
Drained the box and there was 700ml left in there, I had filled to around 850ml.

This gearbox seems to act like an oil pump in action, the alloy chamber is situated just under the rear hatch inside the bumper, so much higher than the top of the box, and it still managed to fill that fuel filter housing and push through the foam, dumping 150ml of oil. Unbelievable. No wonder MG's silly little revised breather doesn't work !

Sooo, today I threw the last dice. Blanked off the factory breather hole and fitted an adapter in the fill hole in the side of the box, well above the left CV joint.
Fitted the same hose on that after I cleaned it of oil and filled the box with 850ml yet again ( I now probably have the freshest gear oil in the country )

I've only done around 50 miles so far but I think I might be on to something. There's NO oil in the pipe so far, it doesn't seem able to push it up the initial few inches towards the underside of the boot floor far less up behind the back bumper.
Maybe I've actually lanced the boil at last and the pressure is gone ?
Will see how she blows over the weekend

Hats of for persevering, can't believe this is still getting downplayed by some

 

[Macadoodle]

Hats of for persevering, can't believe this is still getting downplayed by some

Cheers. The only caveat I would offer to those thinking MG has solved this problem is if you have the same gearbox that's fitted to my SE SR it ain't got 750ml in there as the dealers claim, no frigging way.
It seems to stop it's forceful vomiting around the 700ml mark, but I'm not sure it's totally done even then.
This is with 1.5 metres of 6mm tubing terminated with an oil catch can high behind the rear bumper mind you My car puked its way down to a gross black 600ml with the factory set up.

The 64 million dollar question of course is just how little oil will the box happily survive with ?
You don't want to fill with more than it needs, the less oil the less parasitic losses and the more miles kWh.
It's a fine line to be sure, but who the hell can you trust to tell the truth ?

 

[WalkingBootWeather]

who the hell can you trust to tell the truth ?

Gary Lineker?

 

[Les burrows]

Hi Macadoodle
I have just read your post at #2711 yeh #2711 for God’s stakes, and I had been thanking along these lines for a good while, as much much earlier in the thread it was being said by many that the problem was down to the oil being thrown at the breather by the crown wheel, and I had thought could a breather not be fitted at some other point away from the crown wheel, well now I see you have done this and I wish you all the luck in the world with it, and if this does do the job I will be the first to buy you for all your efforts. I’m 99.9% sure this should do the trick if the cause is oil being thrown at that breather fitting which you have now blanked off, I just hope there’s no build up of pressure that might blow an oil seal elsewhere in the unit, but it shouldn’t have much pressure in any case and should still vent air from the new breather position if there is. Good Luck.
Les

 

[Hagen]

I agree with you Les, great job done by Macadoodle. But ...
Why didn't came MG with this 'simple' and cheap solution? And why are not all cars from the first batch seem to have this leaking problem?

 

[the briggie]

And why are not all cars from the first batch seem to have this leaking problem?

Probably a number of reasons. After initial issue was discovered MG probably lowered fill levels. Also some don't drive the car hard and it may not spit. Others may not even have noticed it....and some may just be lucky

 

[TheHypnoToad]

I assume changing the oil on the reduction gears isn't a service item?

If it is, it would be interesting to see how much oil is drained from cars which don't have the leak.

 

[Deleted member 10041]

If I remember correctly it doesn't/shouldnt need changed. The fact that @Macadoodle only drained 600ml out of his and it was already a horrible black colour after 6 weeks is concerning.

It would be really interesting to find out what someone with the same car and from the early batch, who's never had the leak could drain out of theirs to compare.

 

[horse7]

Has MG UK issued any statements about whether this oil leak is now resolved or is still under investigation, and is the leaking part being used by other cars either in the mg range or other cars, also who makes the part, in house or other?

 

[siteguru]

I reported it as an issue to DVSA. My dealer has reported my leak to MG (note: I've already had the breather mod) but there's been no feedback yet. (It's been 3 weeks).

 

[Les burrows]

I assume changing the oil on the reduction gears isn't a service item?

If it is, it would be interesting to see how much oil is drained from cars which don't have the leak.

No l don’t think it is or at least not until quite a high mileage.
And there is apart from draining it down to check there is no means off checking it for amounts or condition.

I asked the service reception ( don’t get to speak to the to the people who are doing any work on the car theses days in many dealerships ) when the breather was changed do you know how much oil was put in after, answer was they will have top it up to the correct amount,which is I said,no answer other than it will be at the correct level.
Les.

 

[Hagen]

I assume changing the oil on the reduction gears isn't a service item?

If it is, it would be interesting to see how much oil is drained from cars which don't have the leak.

Its supposed to stay in the transmission box for lifetime (about 180.000 km)

 

[Macadoodle]

Hi Macadoodle
I have just read your post at #2711 yeh #2711 for God’s stakes, and I had been thanking along these lines for a good while, as much much earlier in the thread it was being said by many that the problem was down to the oil being thrown at the breather by the crown wheel, and I had thought could a breather not be fitted at some other point away from the crown wheel, well now I see you have done this and I wish you all the luck in the world with it, and if this does do the job I will be the first to buy you for all your efforts. I’m 99.9% sure this should do the trick if the cause is oil being thrown at that breather fitting which you have now blanked off, I just hope there’s no build up of pressure that might blow an oil seal elsewhere in the unit, but it shouldn’t have much pressure in any case and should still vent air from the new breather position if there is. Good Luck.
Les

Yep, I suspected as much too, couldn't get my head around how the designers had got it so wrong though, so I thought I would persevere with the factory breather location.
Considering the small internal volume of the unit and the pretty minimal thermal expansion of the the air and fluid inside, there cant be much pressure in reality, so that only leaves 'sling' as the cause .

Having looked at the new setup this morning, there's around an inch of fluid residue in the pipe as it exits the box horizontally so it gives me confidence that it's breathing freely, but none up the vertical section towards the boot floor.
If this holds over the weekend I think I'll try stripping out the rear bumper 1.5 metre pipe run and just have a short vertical section terminating at the boot floor , think that's all it might need with this.

 

[siteguru]

Are you still using the expansion box?

 

[Macadoodle]

Are you still using the expansion box?

Yep, still on there. Will try it without with the new setup. I have a brass 90 degree elbow pipe connector on order to screw into the fill plug adapter, I think I'll try a simple bung with a small hole on the end of a short pipe between the two.
Pipe connector I have fitted at moment is straight and horizontal so is allowing a little oil to flow into the tube before it turns up towards the boot floor, seems to be going no further though.
Can't quite believe the difference so far , chalk and cheese.

 

[Les burrows]

Macadoodle if this holds please ho please send what you have found to MG with photos or drawings so they can get their people trained up on how to sort this issue I’m getting a little old and stiff for being under cars now so my dealer will have the task of fixing it.
So fingers X it holds makes perfect sense to me like I said earlier. Well done.
Les