Found out what’s causing undercarriage composite to break apart

[AlanSubie4Life]

So far:
I see a lot of worry about this lining breaking apart and I am not sure why.

I haven’t seen anything here that suggests that the lining is not weather capable, and it does not seem particularly absorbent. It’s not cardboard. It can be soaked and maintain full strength as far as I can tell on my car.

The issues I see are:
1) Bolts must be present and tight enough to not loosen. I need to look up a torque spec on a torque chart, but mine were at 2ft-lbs which is not enough. If any come off damage can occur.

2) in winter, possibility of snow chunks from tires dumping on top of the cover weighing it down enough to rip it off. It is hard to tell without having the vehicle lifted, but to me it looks unlikely that this is a problem.

3) the rear bumper cover can fill with a lot of water (and freeze) when parked facing uphill. When level, there doesn’t seem to be an issue. The bumper cover also has two bottom bolts that must be present and tight. The middle one has no hole AFAIK.

The bumper cover issue seems unrelated to the composite axle cover issue to me, though they have the common theme of loose bolts causing problems. The composite sheet doesn’t appear to accumulate water from what I have seen in all the prior videos and the other thread.

Best thing you can do here, in my opinion, is to immediately check that all bolts and washers are present and tighten them to the torque spec.

 

[outdoors]

Hmm... I just checked mine and there was a screw/bolt there but it was barely in there, probably with more driving it could just wiggle loose and fall out.

View attachment 354461

I just finger tightened it back down, and will consider what to do next. I am thinking about drilling drain holes, but want to give it a bit more thought first.
Also, thinking maybe those screws need some better way to stay put. Perhaps some kind of thread locking compound / glue.

Vin 2201

Have center bolt and it is tight. Also have all the clips in the wheel wells that newer cars are missing. As I said earlier. At SC inspected many cars with both clips and center bolt missing. Strange.....

 

[bonaire]

Conspiracy theory may say that they built some of the rushed cars in Sept and June without some bolts and such, intending to install them before delivery but it wasn't part of the final-check process or not all service centers are checking.

Sounds like all bolts, which are missing should be installed and not called-out by new-buyers. Otherwise, the end result is a customer-charged comprehensive-insurance repair that may have to be "fought" to be made right. It's now a new checkbox to look at when people are picking up their cars when-new.

 

[Lon12]

I had clips missing. The one I've circled in this picture adds a lot of rigidly to the lower shelf as it attaches there as well. I noticed it moved up and down a lot before the clip was inserted.

 

[AlanSubie4Life]

Vin 2201

Have center bolt and it is tight. Also have all the clips in the wheel wells that newer cars are missing. As I said earlier. At SC inspected many cars with both clips and center bolt missing. Strange.....

Interesting. I'll have to double check this (it is difficult when the vehicle is not on a lift), but the center bolt hole for the rear bumper cover does not appear to exist on my vehicle (081xxx) - but perhaps it is just misaligned enough that I couldn't feel it or see it.

I've noticed the missing fender shield retainers and I'll probably just buy some rather than arguing with the service center about them. Looks like adding them can't hurt, the fender lining does move a little bit without it but it doesn't seem like that big a deal. But if you're hitting the fender liner with huge chunks of snow, and it's accumulating frozen slush, maybe it's best for it to be attached as well as possible. I'm in California, so, shrug.

Mine is an October build so I don't think the "rush" hypothesis works. It's possible it was just cost reduction, but it seems a bit odd. Not a lot of cost!

 

[AlanSubie4Life]

Has anyone measured these fender shield retainer plastic "rivets"/"push pins"/"pop-its"? Hole diameter, stem length, flange diameter? I guess I'll go pop out one of the ones I have at some point and get a caliper on it if not...

 

[SMAlset]

The bumper doesn't fall off, but the bumper cover can come off. (Though we have only see reports of that when fording water.)

Distinction noted (not a car person ). But anything falling off a vehicle unintended would be a safety issue, at least I would consider it to be.

Our Model 3 is a Sept build, 088xxx. My husband tried to examine and take photos of the underside before it rains here but said he couldn't get a good photo and see much due to the underside being so close to driveway surface. He did say that our middle of the 3-bolt area does not have a bolt in it.

As to the wheel well holes, we had some but had that on our due bill and they were taken care of then.

 

[reheat]

Has anyone measured these fender shield retainer plastic "rivets"/"push pins"/"pop-its"? Hole diameter, stem length, flange diameter? I guess I'll go pop out one of the ones I have at some point and get a caliper on it if not...

I bought a set of the plastic fasteners on amazon that come with different sizes and used the ones that fit.

 

[Eno Deb]

Just checked mine and I am missing the center bolt. BUT there isn’t even a female threaded hole for the bolt to screw into. For those missing center bolts, do you have a corresponding hole there to thread a bolt into? Looks like a design change where there is a hole in the middle but mounting point was removed. Kinda like the fender liners that have holes but no corresponding hole in the fender to install fender plugs.

Same here. I have no bolt (and no threaded hole) in the middle. I have a threaded hole in the left and right ones, but the right bolt is missing. Nothing feels loose though.

Left:

Middle:

Right:

 

[AlanSubie4Life]

Same here. I have no bolt (and no threaded hole) in the middle. I have a threaded hole in the left and right ones, but the right bolt is missing. Nothing feels loose though.

It's really amazing that these aren't tightened properly! Probably creating a lot of road hazards with bolts flying out. Definitely get this bolt & washer put back. Once you have 10-20 pounds of water (or ice) in your bumper cover, you're going to want it firmly attached in as many places as possible.

 

[Redrick00]

Have to admit I find this worrisome. We are going to be getting rain and my Model 3 is parked outside on a driveway with a slant (typical for homes in this area to sit above street level to prevent flooding in homes).

If parked front in and I assume my car is just like OPs, the water will build up in the rear bumper panel until the car is moved. Could see where the additional water weight can be a problem and really don't want my bumper to fall off. BTW it is a safety issue if you don't have a bumper.

If parked rear in the water will still fall into the bumper and the guess is would send the water into the lining due to the slanted nature of the car on the driveway. Don't really have any where else to park my car, and even parked in a level parking lot or driving on the street it looks like water will still get inside if like OPs.

Since the cars are constantly being modified am wondering if this was caught early at some point and redesigned. OP, what mfgr date is your car? Have you spoken to service about this yet?

My car has mfd 07/18 VIN 49xxx. I have not spoken to service as I just found this out a few days ago. I looked into it because I would always find a long streak of water down my driveway when backing out after washing the car.

 

[SMAlset]

I'm thinking if you have a selfie stick and set the cellphone camera to flash you might get some decent underbody photos.

 

[Redrick00]

I had clips missing. The one I've circled in this picture adds a lot of rigidly to the lower shelf as it attaches there as well. I noticed it moved up and down a lot before the clip was inserted.
View attachment 354615

Those are also missing on mine, rear both sides. I don’t think they’re as important as the bumper cover ones but I do plan on putting them on eventually.

 

[AlanSubie4Life]

My car has mfd 07/18 VIN 49xxx. I have not spoken to service as I just found this out a few days ago. I looked into it because I would always find a long streak of water down my driveway when backing out after washing the car.

Just park your car pointed downhill when washing, or when rain is expected. The underbody cover isn’t a concern, as far as I can tell. As long as it is attached. My friend suggested that Tesla will provide a software update to remind you which way to park when rain is in the forecast. What other car company can do that!

Just did a quick survey of the Model 3s in our garage.

Rear bumper cover:
Older RWD vehicles delivered in ~March/April have three bolt holes. One that I looked at had the middle bolt, but was missing both of the outer bolts.
My P3D, October build, has no hole for the middle bolt, but has both of the outer bolts.

My car:
It's missing a bolt on the front undercarriage cover which I noted at delivery.

The rear undercarriage cover has more bolts than I thought - I think it actually has 6 on the leading edge, and at least 2 on the trailing edge, I think. I found a car in the garage without one of these bolts, makes it very floppy on the corner. Seems very common.

 

[Eno Deb]

It's really amazing that these aren't tightened properly! Probably creating a lot of road hazards with bolts flying out.

My guess is that the factory "forgot" to put in the missing right bolt in the first place. But the middle bolt appears to be a design change since there is no threaded hole behind it. Perhaps their attempt to provide a drain hole?

 

[AlanSubie4Life]

My guess is that the factory "forgot" to put in the missing right bolt in the first place. But the middle bolt appears to be a design change since there is no threaded hole behind it. Perhaps their attempt to provide a drain hole?

Based on how loose mine were, and the pictures earlier in this thread showing loose bolts, I doubt they were forgotten. They simply walk themselves out. It's possible the use scenario is such that threadlocker will be required. I'm not an expert on fasteners, but in the right situations, even very tight bolts can work themselves free.

 

[Eno Deb]

Based on how loose mine were, and the pictures earlier in this thread showing loose bolts, I doubt they were forgotten. They simply walk themselves out. It's possible the use scenario is such that threadlocker will be required. I'm not an expert on fasteners, but in the right situations, even very tight bolts can work themselves free.

After taking another look at the picture I posted earlier, I think you are right. If you look closely there is a circular imprint around the right hole right where the washer would have been. The middle hole, on the other hand, looks completely untouched.

 

[Redrick00]

So far:
I see a lot of worry about this lining breaking apart and I am not sure why.

I haven’t seen anything here that suggests that the lining is not weather capable, and it does not seem particularly absorbent. It’s not cardboard. It can be soaked and maintain full strength as far as I can tell on my car.

The issues I see are:
1) Bolts must be present and tight enough to not loosen. I need to look up a torque spec on a torque chart, but mine were at 2ft-lbs which is not enough. If any come off damage can occur.

2) in winter, possibility of snow chunks from tires dumping on top of the cover weighing it down enough to rip it off. It is hard to tell without having the vehicle lifted, but to me it looks unlikely that this is a problem.

3) the rear bumper cover can fill with a lot of water (and freeze) when parked facing uphill. When level, there doesn’t seem to be an issue. The bumper cover also has two bottom bolts that must be present and tight. The middle one has no hole AFAIK.

The bumper cover issue seems unrelated to the composite axle cover issue to me, though they have the common theme of loose bolts causing problems. The composite sheet doesn’t appear to accumulate water from what I have seen in all the prior videos and the other thread.

Best thing you can do here, in my opinion, is to immediately check that all bolts and washers are present and tighten them to the torque spec.

Today while searching I found a thread where they had problems with undercarriage during rain. I posted photo showing where mine dripped and where the person on linked thread had the problem. When I recorded my videos the front of car was about 3” higher than rear because of driveway slant. If I was to park reverse, then I’m sure water would of flowed all the way forward to where the composite broke down on linked thread.

 

[Redrick00]

View attachment 354684
Today while searching I found a thread where they had problems with undercarriage during rain. I posted photo showing where mine dripped and where the person on linked thread had the problem. When I recorded my videos the front of car was about 3” higher than rear because of driveway slant. If I was to park reverse, then I’m sure water would of flowed all the way forward to where the composite broke down on linked thread.

View attachment 354684
Today while searching I found a thread where they had problems with undercarriage during rain. I posted photo showing where mine dripped and where the person on linked thread had the problem. When I recorded my videos the front of car was about 3” higher than rear because of driveway slant. If I was to park reverse, then I’m sure water would of flowed all the way forward to where the composite broke down on linked thread.

Ripped Undercarriage Composite from the rain?

 

[AlanSubie4Life]

View attachment 354684
Today while searching I found a thread where they had problems with undercarriage during rain. I posted photo showing where mine dripped and where the person on linked thread had the problem. When I recorded my videos the front of car was about 3” higher than rear because of driveway slant. If I was to park reverse, then I’m sure water would of flowed all the way forward to where the composite broke down on linked thread.

I understand and am familiar with that thread. But I suspect this is only a problem after a significant number of bolts fall out (which they likely will), and then the whole thing collapses due to rain, wind, and snow.

I don’t think the composite broke down. It got ripped off because it wasn’t properly attached. That is just a guess on my part.

I’d like to see a case where there is damage to this cover but EVERY bolt and washer is still present and tight. Then we could suspect the cover material.