MG4 Undertray dip/bulge

[tsedge]

Sorry, but that is such rollocks.

The whole motor/gearbox assembly is not designed to be exposed to road sh*te, particularly the salt/grit that we have at this point of the year. Most front engined cars have had undertrays as standard for the last 20 years. The amount of stuff that gets flung up onto the rear underside is so much more than the front underside gets, so any issues will be much worse.

I am utterly gobsmacked, and having checked that this isn't 1st April, can honestly say this is one of the most crass pieces of overriding an engineering decision that I have ever seen.



That may have been the driver with diesel engined ICE where aero efficiency is less of an issue than it is on EVs, but that's also related to the airflow through the outrageously large radiators required for the heat rejection with ICE.

I'll put forwards an alternative suggestion. The undertray catches and concentrates any oil leak into one area, and then the oil flows back along the visible underside of the undertray making it obvious that the issue is occuring. Without an undertray most of the oil will fall out onto the road never being seen, a leaving the owner blissfully ignorant. So removing the undertray kills two birds with one stone.

I thought the MG5 originally didn’t have an undertray and that was fine without?

I really think you are overstating the importance.

 

[nivs123]

The reasons I have heard are:

• Aerodynamics: small improvement
• Dirt: protect motor from build up of dirt (questionable if it actually achieves this)
• Noise: minor reduction

It most certainly is not structural or in any way protection for the underside of the car: you’d need a thick bash plate for that.

• Dirt: protect motor from build up of dirt (questionable if it actually achieves this) = Really?

 

[FiferMG4]

Just collected my MG4 SE SR, and the solution to a bulging undertray is... No undertray

Just waiting for a copy of the email from MG to dealers advising it is to be removed on all deliveries now, have advised the dealer if I don't get this I want my undertray please

View attachment 13719

@stuartthomas has commented under his video that a replacement for his defective undertray is on order from his dealer. I think you should request the same Ayoull. I certainly wouldn’t be happy about a piece of the car I’d paid for being missing.

 

[Ayoull]

@stuartthomas has commented under his video that a replacement for his defective undertray is on order from his dealer. I think you should request the same Ayoull. I certainly wouldn’t be happy about a piece of the car I’d paid for being missing.

Having spoken to MG on the phone they've confirmed it is correct based in what is recorded on their system, I have emailed MG for their official take on it in writing and have included the picture of my absent undertray

 

[tsedge]

• Dirt: protect motor from build up of dirt (questionable if it actually achieves this) = Really?

Depends on situation … there are some horror stories online of undertrays jammed up with earth and dirt because it gets in and can’t get out again.

 

[nivs123]

Depends on situation … there are some horror stories online of undertrays jammed up with earth and dirt because it gets in and can’t get out again.

Aye, but if they're built and fitted incorrectly with dirty great scoops - that'll happen

 

[Deleted member 10041]

I thought the MG5 originally didn’t have an undertray and that was fine without?

I really think you are overstating the importance.

I think the point here is that there is an issue with poor fitting trays, that were obviously originally designed and fitted for a reason, MG's answer now is to just remove them, seems a pretty shoddy solution to me

 

[AndyL61]

At least it will make the oil leak easier to see and fix .

 

[tsedge]

I think the point here is that there is an issue with poor fitting trays, that were obviously originally designed and fitted for a reason, MG's answer now is to just remove them, seems a pretty shoddy solution to me

They may have decided to remove the current design because it is defective and be planning to add in the new design they have said they are testing. So this may be an interim solution.

 

[tsedge]

Aye, but if they're built and fitted incorrectly with dirty great scoops - that'll happen

Yes, that’ll make it worse but even on makes with perfectly flat trays the dirt still gets scooped up from the road and trapped:

 

[nivs123]

Yes, that’ll make it worse but even on makes with perfectly flat trays the dirt still gets scooped up from the road and trapped:

All that's left is to agree to disagree.

 

[Ian Key]

Until proved otherwise I suspect the removal of the undertray is another case of dealer BS.

 

[Ayoull]

Until proved otherwise I suspect the removal of the undertray is another case of dealer BS.

MG confirmed over the phone it is correct, but awaiting email from MG Motors UK head office

 

[maverickz]

Just collected my MG4 SE SR, and the solution to a bulging undertray is... No undertray

Just waiting for a copy of the email from MG to dealers advising it is to be removed on all deliveries now, have advised the dealer if I don't get this I want my undertray please

View attachment 13719

Undertray issue? What undertray?
No such issue on your car.

 

[Rip Van]

MG confirmed over the phone it is correct, but awaiting email from MG Motors UK head office

My MG4 is due at the end of January. If it doesn't have an undertray, has an undertray with bulge(s) or no modified breather fitted, I'll be delaying or cancelling my order.

 

[Macadoodle]

My MG4 is due at the end of January. If it doesn't have an undertray, has an undertray with bulge(s) or no modified breather fitted, I'll be delaying or cancelling my order.

I wouldn't to be honest, it's a good little car. The breather mod seems to have solved the oil drip, and the frilly undertray is small potatoes IMO.
Have had my 4 SE for 3 days and had a peek at the underside yesterday. Yup, slightly wavy leading edge on the undertray, doesn't really concern me TBH.
I like solving problems so if there's no dealer mod by the spring, I think I'll devise some sort of strengthening strip from aluminium that can be fitted to the forward edge to permanently support it and keep the crinkles at bay.
Doubt they'd be petty enough to consider that an unauthorised mod and void the warranty but who knows of course

 

[Auto Surgeon]

I had a good look at the under trays in the dealership yesterday, both had the bulge. To me it looked more to be caused by a heat/too thin abs plastic issue more than fitment. The dealer said he didn't think it was heat from the car as it had only been driven 2 miles so possibly heat from sitting in a hot environment on the ship & the thin plastic warping. A redesign with an internal rib structure or thicker plastic should sort that.

 

[Rip Van]

I like solving problems so if there's no dealer mod by the spring, I think I'll devise some sort of strengthening strip from aluminium that can be fitted to the forward edge to permanently support it and keep the crinkles at bay.

My initial thoughts exactly, I've got enough left over aluminium angle from other projects to do the job. I'll keep an eye on the other issues, reported on here, until I get the call.

 

[Ayoull]

Confirmation that my undertrayless MG4 should have an undertray and I've emailed and called the dealer to find out when I can get my under car air scoop fitted

 

[Macadoodle]

Taking advantage of the thaw yesterday, I put the rear of my car up on ramps to check out the extent of the oil leak now appearing, and have a close look at the tray.
The problem seems to be related to the amount and positioning of the fasteners used to secure it, it has very poor support at the leading edge.
The tray just forward of the problem one (battery one) is far better served with fasteners right on the edge as they should be, and I think a strengthening strip bridging the two using the battery trays' fasteners to secure might have some promise.
If we get a spell of dry weather I think I'll have a play and I'll post pics, garage is full of crap so I have to work on the wet drive