MG4 Reduction Gearbox Oil Leak

[WigglePig]

That test must have taken hours on the rolling road.

Two in the same bay and yes, they took a while. Once the 5 was done (lower range of course) the Ami was run up...that machine is a MONSTER!

 

[Cocijo]

At least you don’t have to worry about exhaust extraction.

 

[WigglePig]

At least you don’t have to worry about exhaust extraction.

The Big Fans were on anyway, for cooling and enabling the fetching flicking of hair in the breeze.

 

[Hagen]

The issue is NOT caused by excessive heating but by the positioning of the breather fitting directly in line of the crown wheel oil fling. As things heat up the expansion of air/oil in the 'box seems to push tiny blobs of oil out of the breather after they are thrown into the channel.

That's a much better cause then overheating but still hard to solve?

 

[tsedge]

That's a much better cause then overheating but still hard to solve?

Not really, it should be possible to create a breather design which copes with this - but not the current fix.

 

[Cocijo]

Internal baffle would help - but I guess a bit late for that and too expensive as a retro-fit. MG want a fix that will get them out of trouble with the least cost.

 

[tsedge]

Internal baffle would help - but I guess a bit late for that and too expensive as a retro-fit. MG want a fix that will get them out of trouble with the least cost.

I've sent my design with detailed drawings to MG, royalty free.

 

[Cocijo]

Great design! It follows a similar principle to this;

 

[WigglePig]

That's a much better cause then overheating but still hard to solve?

Not at all hard, many gearbox units suffer in the same way, hence the widespread use of expansion vessels to catch the oil and allow it to drain back as necessary.

Internal baffle would help - but I guess a bit late for that and too expensive as a retro-fit. MG want a fix that will get them out of trouble with the least cost.

It might well be the case that the internal end of the breather could have a deflector attached to it although I'm not clear if there is sufficient space.

 

[Hagen]

I've sent my design with detailed drawings to MG, royalty free.
View attachment 15375

I prefere this one ...

 

[Cocijo]

MG really are missing a trick here. They could modify the bulging under tray so that it catches any displaced oil - job done! Both issues resolved!

 

[WigglePig]

I prefere this one ...View attachment 15377

Pretty but £££

 

[Hagen]

Pretty but £££

€125

 

[WigglePig]

€125

Oh, OK. That's only about £7500 since Brexit happened.

 

[Hagen]

No worry bill goes to MG UK ?

 

[Macadoodle]

Patented Macadoodle oil breather fitted today, zero leaks so far after 40 miles, some on 70 mph section.

 

[Ayoull]

Patented Macadoodle oil breather fitted today, zero leaks so far after 40 miles, some on 70 mph section.View attachment 15381

How far up the pipe has the oil gone?

 

[Macadoodle]

How far up the pipe has the oil gone?

Not sure as yet, will give it a peek tomorrow if I have time. Hopefully the oil will leave a trace and I can possibly reduce the 12 inch length (ahem)
There's only around 5 inches free space above the breather outlet before you hit the boot floor so I've had to coil it a bit, cable tied the end with the original breather to a bracket.
Tons of empty space below the rear seat however, so you could terminate it there high above the gearbox if necessary.
Ended up using a hose, clips, and a bit of m10 hollow threaded tube I had lying around the garage so have spent nothing in reality.

The 4 'box ejected about 1.5 ml of oil over the test whereas the 5 ejected none (not a surprise) but there was a tiny touch of noticeable oil mist when fully heated.

Interesting stuff. I presume the 5 had a length of tubing 'tween 'box and breather as is more normal ?

 

[WigglePig]

Interesting stuff. I presume the 5 had a length of tubing 'tween 'box and breather as is more normal ?

No, the 5 has a very similar breather to the 4 (but plastic) directly on the casing, albeit not in line with the ring gear!

 

[Macadoodle]

No, the 5 has a very similar breather to the 4 (but plastic) directly on the casing, albeit not in line with the ring gear!

Ah ok, they must have thought, well it worked this time, so why not. The motor output shaft on the 4 is below the breather and I think it's gear is low enough to be in the oil bath looking at the bearing end cap position but I might be wrong.
The intermediate gears are higher up, the ring gear is deeply submerged of course, can see the bottom of it through the drain plug.
Oil could be firing from all directions I guess.
Just surprised talented designers could have thought that the 4's set up wouldn't leak. Tiny breather with a 4mm gravity ball valve you can easily push by just blowing, how was that ever going to work.