MG4 Undertray dip/bulge

[OriginalBigAl]

At my dealers the other week there was a crash damaged MG4 in with the skips at the back of the building containing plastic parts ,trims etc. As this model becomes more popular there will be more secondhand parts becoming available. Start with Ebay , and maybe other forum members will have suggestions.

 

[NLMGSAN]

Mine has only a minor bulges around the center bold. This a brand new car. Got it yesterday.

 

[Fogey]

I see where you are coming from, but just because it can't be seen, doesn't make it acceptable and I would hate to be driving around with a potentially costly time-bomb under my car. From what I have heard it's a £700 replacement part.

That, more than anything else, has finally put me off buying an MG4, I'm afraid.

 

[NLMGSAN]

These issues and the fact that they do not replace it under warranty may explain the poor rating of the mg4 in the WhatCar reliability survey.

 

[tsedge]

Prices seem to vary - I have heard £200 from someone else.

That, more than anything else, has finally put me off buying an MG4, I'm afraid.

Fair enough, wish you good luck with whatever you choose instead.

 

[NLMGSAN]

Just a question to those with a bulging undertray: do you experience noises/rumbling above certain speeds?

The general idea behind this question is that air flows underneath the car. At certain speeds air moves in above this plastic tray. This air flow could cause it to resonate (and possibly break).

 

[OriginalBigAl]

I did my own fix on mine which was not that bad ,but bad enough. Its on another but related post on this forum, but an alternative is to take off the plastic undertray and take it to your local sheetmetal shop who could make up a new one in in stainless or aluminium with built in stiffened edges.

 

[tsedge]

I did my own fix on mine which was not that bad ,but bad enough. Its on another but related post on this forum, but an alternative is to take off the plastic undertray and take it to your local sheetmetal shop who could make up a new one in in stainless or aluminium with built in stiffened edges.

I like this idea! But it surely isn't low cost.

 

[Fogey]

Prices seem to vary - I have heard £200 from someone else.

Fair enough, wish you good luck with whatever you choose instead.

Thanks for that. Yeah, it's a pity, because the MG4 is one of the best looking cars on the road, in my opinion - and it drives to match.

 

[Burgo]

So new MG4's still arrive the same fault?

Picked up our new Luxury (equiv. UK Trophy) here in Spain on 26 Dec (normal working day here!) and it too had the "bulge". Pointed out to the dealer while still in the showroom and asked him to make a note of it, and to let me know when they had the replacement part(s) required.

 

[turntoport]

Just a question to those with a bulging undertray: do you experience noises/rumbling above certain speeds?

The general idea behind this question is that air flows underneath the car. At certain speeds air moves in above this plastic tray. This air flow could causes it to resonate (and possibly break).

Yes, that's a reasonable expectation. The effectiveness of the 'engine air scoop' * is reduced slightly because the laminar/ turbulent boundary layer is probably a centimetre or two thick at that position 'aft'. ( I could calculate it but 1-2cm seems a decent guesstimate). However... going through a deep water 'wade' (only deep enough to catch the bulge lip) will probably cause your tray to join the departed with immediate effect.
*[Following the long run through the grotty midlands in weather, I see a large muck-watermark at both rear door/wing panel gaps; it seems some air 'bleed' is getting out the bodywork there - I wonder if this is a pressurised vent from the undertray scoop?]

Would the undertray issue be resolvable by a class action? Is there any other way to fix this?

 

[Macadoodle]

I did my own fix on mine which was not that bad ,but bad enough. Its on another but related post on this forum, but an alternative is to take off the plastic undertray and take it to your local sheetmetal shop who could make up a new one in in stainless or aluminium with built in stiffened edges.

Would probably work but sounds kinda spendy. I just flattened the problematic central bulge with a bit of thin alloy plate I had lying around, had the effect of bridging the rear undertray to the battery undertray, just used the same screws and fixing points to sandwich it all together.

I've had no issues in the 7 or 8 months since I did this free mod, despite going through some pretty serious floods recently

In the spring, I think I'll get her up on the ramps again and fit a continuous aluminium strip the entire width of the undertray as I'm not hopeful of getting a warranty repair should it make a break for freedom.

 

[NLMGSAN]

Yes, that's a reasonable expectation. The effectiveness of the 'engine air scoop' * is reduced slightly because the laminar/ turbulent boundary layer is probably a centimetre or two thick at that position 'aft'. ( I could calculate it but 1-2cm seems a decent guesstimate). However... going through a deep water 'wade' (only deep enough to catch the bulge lip) will probably cause your tray to join the departed with immediate effect.
*[Following the long run through the grotty midlands in weather, I see a large muck-watermark at both rear door/wing panel gaps; it seems some air 'bleed' is getting out the bodywork there - I wonder if this is a pressurised vent from the undertray scoop?]

Would the undertray issue be resolvable by a class action? Is there any other way to fix this?

Can you show us the specific location for the 'air bleed'?

 

[bikerbear1]

View attachment 11913
Am I winning for lowest car ? I know in my 20s having a lowered car was cool.

 

[bikerbear1]

Had an update from MG (after a small chase) Apparently a communication has been sent out to dealers this morning, asking any cases to be reported so they can get an idea of numbers etc.

At least it’s on their radar properly now

I have been told by mg that’s it’s not a manufacturer defect and they won’t rectify it

 

[bikerbear1]

Had an update from MG (after a small chase) Apparently a communication has been sent out to dealers this morning, asking any cases to be reported so they can get an idea of numbers etc.

At least it’s on their radar properly now

I have been told by mg that’s it’s not a manufacturer defect and they won’t rectify i

Any updates from MG about the undertray?
Is there a fix or is it being ignored?

 

[bikerbear1]

Has anyone heard any more about an undertray fix from your dealer (those affected only, please)?

Yes I had email from mg customer service they don’t accept it’s a defect

 

[Rolfe]

No. That's about average. Similar to mine.

How odd. The reply function isn't including the quote on my phone.

 

[NickHeynes]

Yes I had email from mg customer service they don’t accept it’s a defect

If they won't accept it's a defect how come there's a fix for it ?

 

[tsedge]

If they won't accept it's a defect how come there's a fix for it ?

I agree with you.

It seems as if:

• If the sag is minor, they declare it not a fault and "as designed", which is perfectly true, albeit it is a crap design.
• If the sag is major, they have been replacing the undertray in many cases (not all).
• The new piece of metal may be a cheaper solution than replacing the undertray, but I expect for cost reasons they will still reject minor sagging.