Found out what’s causing undercarriage composite to break apart

[AlanSubie4Life]

Yes, both weatherstripping designs keep water out of trunk, I’ve never had water in mine.

This is what I get for replying before coffee. I misinterpreted what you were saying.

Seems like this is mostly an aesthetic modification to the seal, to stop people from complaining about gaps. Perhaps it is superior in other ways too. I guess the customer is always right!

 

[TEG]

And another report:

Small section of undercarriage liner torn out

 

[AlanSubie4Life]

@Redrick00,

Is this the same wide gap to bumper in the lower left/right corner of the trunk/seal as in my photos? Have a Ranger coming tomorrow to look at same issue.

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Regarding this gap, other than the aesthetic issue, it really is not a problem. This is what Tesla techs have said as well.

I helped @Daniel in SD today with his hitch (partial) install. Here are a couple pictures of this area on the left hand side.

You can see that this seal, new design or not, really will do nothing to prevent water from reaching the rear bumper cover, nor is it necesssary for sealing the trunk. This can also be seen in hitch install videos online.

Water can go just flow down in this area, it’s really not an issue unless it subsequently freezes in large quantities in the bumper cover.

A fair amount of dirt could accumulate in the bottom of the cover but even that should be largely self-limiting, unless you take the car mudding (not recommended). For normal use, wash the car while it’s pointed downhill, or park downhill in a rainstorm - should help flush any dirt out and allow good drainage.

 

[Redrick00]

Regarding this gap, other than the aesthetic issue, it really is not a problem. This is what Tesla techs have said as well.

I helped @Daniel in SD today with his hitch (partial) install. Here are a couple pictures of this area on the left hand side.

You can see that this seal, new design or not, really will do nothing to prevent water from reaching the rear bumper cover, nor is it necesssary for sealing the trunk. This can also be seen in hitch install videos online.

Water can go just flow down in this area, it’s really not an issue unless it subsequently freezes in large quantities in the bumper cover.

A fair amount of dirt could accumulate in the bottom of the cover but even that should be largely self-limiting, unless you take the car mudding (not recommended). For normal use, wash the car while it’s pointed downhill, or park downhill in a rainstorm - should help flush any dirt out and allow good drainage.

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After further inspecting the undercarriage on Saturday I agree with you that broken composite panels must happen from missing or loose bolts. Water on bumper cover should only be a problem if seep holes clog up on composite panel or if water freezes inside bumper cover. I enlarged drain hole on my bumper cover and it now drains without any water overflowing to composite panel. I sprayed water on car for a few seconds and it all drained pretty fast from enlarged hole. I can only imagine how much water flows through there during a rainy day, thankfully I live in Southern California where it hardly ever rains. Like you say, pointing car downhill during rain will help flush water out but driving during rainstorm will have lots of water sloshing around and drive unit is right above the composite panel. I removed rear bolts on composite panel to take photos.

 

[AlanSubie4Life]

Yeah, that's about the right place to drill it appears, if you feel it's necessary. I'm not going to worry about it, but in freezing/wet climates I might think about it. Overall I'd be pretty loathe to drill it though! I've attached a picture of the upper side of where you drilled; you can see there is a lip which would definitely accumulate a little water (which you have eliminated). I suspect eventually a small hole will get plugged by dirt and rocks though (same issue as the undercover will have - you bring up a good point - it may be that if these drain holes get plugged that the water weight would be too much - I'm not sure).

In wet conditions, yeah, it's really hard to predict exactly how these things will behave, it's very hard to know exact how water will be splashed & channeled. All you can do easily is make sure you have all the bolts! Note that for the bumper cover, there is actually one bolt that you can't see, which is located on the forwardmost edge (middle hole in the picture below), underneath the undercarriage cover (this one is unlikely to be missing though since I don't think it can fall out even if it loosens). So there are 7 (2+2+3) (or 8 (2+3+3) for some early cars) attachment bolts on the bottom side of the rear bumper cover. This is explained in most hitch install videos, though sometimes it isn't obvious.

 

[AlanSubie4Life]

Took my car to service center this morning after scheduling an appointment. I was hoping to get some bolts and get a few other cosmetic issues fixed. I am missing one bolt for the front aero shield and one for the rear (aero shield is what they call this composite cover apparently).

Anyway, they were out of bolts! Guess they are in high demand.

However, they found an alternative 9.8 class bolt and washer rather the 8.8 class which belongs there. For my front bolt. They didn’t do the rear bolt because of course they thought I was talking about the bumper cover bolt...but anyway, next time.

Decided not to leave my car at the center, as it was very dusty and they didn’t have the parts anyway. Next time I go back hopefully they’ll have some bolts! The bolts are flying out of these shields faster than they can make them!

 

[Ulmo]

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It's a good idea not to get those parts wet if you can help it. Water would degrade the components. Question is how fast. If it would take 20--30 years to degrade, forget about it. But likely there's some little part that would get mad if you got it muddy, wet, moldy, corroded, etc. well within the expected lifetime of the car. Also, some Model S motors were known to have holes that could get water inside and damage them. After warranty, you could end up with a worthless car just because you decided to skimp on a few pieces of felt (that ought to be stronger, granted, and maybe even an after-market stronger solution, but that could also cause its own issues?). When the plastic liner on my Model S got a hole, that's the consideration I had, since I didn't want the motor and drive shafts full of fine dust that would tear them apart and cause wear, corrosion, electrolysis, etc.

 

[ChrisH]

It's a good idea not to get those parts wet if you can help it. Water would degrade the components. Question is how fast. If it would take 20--30 years to degrade, forget about it. But likely there's some little part that would get mad if you got it muddy, wet, moldy, corroded, etc. well within the expected lifetime of the car. Also, some Model S motors were known to have holes that could get water inside and damage them. After warranty, you could end up with a worthless car just because you decided to skimp on a few pieces of felt (that ought to be stronger, granted, and maybe even an after-market stronger solution, but that could also cause its own issues?).

That sounds like a design deficiency and I would be livid.

 

[Ulmo]

That sounds like a design deficiency and I would be livid.

Only if it's broken. We're talking about holes in the covers right now. Yes, we are not too happy about how easy it is for holes (and tears, etc.) in the covers to develop, and that's what we want to fix, but they are delivered new with the covers intact.

(Short seller alert; this seems like a FUD angle to say this is a huge problem; this is not some major show stopper, since we're talking about 5%--10% of cars experiencing this over their entire life time, and something we hope to see fixed so it's not even that kind of thing. But it is something that needs addressing. Kind of like bad transmissions on a Chevy but way cheaper to fix, the lack of electric cars from Ford, or ICE engines bursting into flames constantly (also way cheaper to fix than that).)

 

[ChrisH]

Only if it's broken. We're talking about holes in the covers right now. Yes, we are not too happy about how easy it is for holes (and tears, etc.) in the covers to develop, and that's what we want to fix, but they are delivered new with the covers intact.

(Short seller alert; this seems like a FUD angle to say this is a huge problem; this is not some major show stopper, since we're talking about 5%--10% of cars experiencing this over their entire life time, and something we hope to see fixed so it's not even that kind of thing. But it is something that needs addressing. Kind of like bad transmissions on a Chevy but way cheaper to fix, the lack of electric cars from Ford, or ICE engines bursting into flames constantly (also way cheaper to fix than that).)

I don’t disagree with that, but Tesla should not be charging to fix this.

 

[bonaire]

I always wash my model 3 on my back yard and noticed that every time I back out after washing there’s a long trail of water about 50’ long right on middle of driveway. This is even after the car sitting there for hours. I looked under car and saw it dripping from rear undercarriage. I started searching online and found photos of other model 3’s with rear bumpers falling off and composite material breaking apart. I then opened my trunk and poured water around weatherstripping seal and water runs off to the sides and down but most of the water runs behind rear tail lights and and ends up inside on the rear bumper. The rear bumper has edges which act as a wall holding a lot of water. Once it fills or during driving water shoots forward drenching the composite material. This will be a big problem for many during winter when all that water on bumper freezes adding weight and stress to rear bumper.

I then drilled a small 5/16” drain hole (hole #1) on center of bumper and poured more water but a single hole was not enough and water still drained off to the composite material. I added two more holes (holes 2&3) close to the first one but no water drained from there so I ended up drilling 2 more (holes 4&5) closer to where bumper meets composite material. One of these last holes (hole #5) ended up being where it drains the best. I did kind of crappy job drilling as drill motor didn’t fit under car so I drilled at an angle. I don’t know it having those holes will hurt the aerodynamic functionality of car but at least I won’t have a bumper full of water.

This reminds me of when my solar PV sytem was installed. The combiner box for the power at the side of the house was installed (to combine the grid wires going into the house. The box was a nice looking box, but had built-in flaws. Number one - no weep holes. Weep holes allow water out. Without weep holes, water collects in such a space during rains. Mine? Water collected, up over the edge and down the 200A 240V line and across my house's breaker box. We would get water in the basement and not know where it was coming from. On occasion, I would sense a bit of water on the breaker. Stumped, I started tracking where it came from and opened the combiner box - which I though was really off limits. Opened it and saw water puddling in there due to now weep holes. Called the solar guys and they immediately came out and helped. At first they balked at fully replacing the power panel but after seeing the issue, no weep holes and the fact that it could have caused major problems due to lack of this issue, they replaced it free of charge. The real kicker was the local engineering guy who "approved the install" had to be paid again to come out and approve the new panel weep holes. Maybe if he inspected *for* weep holes in the past (who thinks of rain on a nice sunny day??) the whole thing could have been avoided.

Engineers work in climates like Michigan at auto firms know four-seasons and design for it. The lack of water weep holes in the bumper in the CA-designed vehicles out there seem to be indicative of the lack of harsh-weather engineering. The bumper should be retro-fitted with shop-installed weep holes and engineered into future cars built ahead of time.

 

[Needsdecaf]

It's a good idea not to get those parts wet if you can help it. Water would degrade the components. Question is how fast. If it would take 20--30 years to degrade, forget about it. But likely there's some little part that would get mad if you got it muddy, wet, moldy, corroded, etc. well within the expected lifetime of the car. Also, some Model S motors were known to have holes that could get water inside and damage them. After warranty, you could end up with a worthless car just because you decided to skimp on a few pieces of felt (that ought to be stronger, granted, and maybe even an after-market stronger solution, but that could also cause its own issues?). When the plastic liner on my Model S got a hole, that's the consideration I had, since I didn't want the motor and drive shafts full of fine dust that would tear them apart and cause wear, corrosion, electrolysis, etc.

Not sure I really agree with this. These plastic / felt undertrays are called aero covers for a reason. They are there to smooth air die for better cD. They are not intended to waterproof the underside of the car as they are not sealed in any way. Many manufacturers use these now.

If water gets past them, the components on the other side are designed for that.

Obviously a hole in the motor is an issue of a different matter.

 

[Perry]

Is this undercarriage something that you can physically rip apart with your hands?

Yes, mine broke up as wind pushed it down and started dragging on the road. I ripped the remaining part with my hand since it was making noise. Some of the bolts where loose and some fell out all together. The material can be ripped by hand. It is not that strong but mine broke probably because the screws became loose.

 

[Perry]

Tesla has new trunk weather seal design, it might be better at keeping the water out.

So what exactly is different here?

 

[Perry]

The new weatherstripping will keep water out of trunk but not out of bumper cover. Water enters bumper from behind tail lights. This is the same seal installed on my vehicle after I found my old one had a wide gap to bumper.

So they fixed the issue with water dripping into the trunk from the rear window glass when trunk is open?

 

[0ptions]

I feel like these bolts must be getting installed by a misconfigured robot, to be done so poorly. I don’t see how a human could do so badly.

Hi! Bolts like this are typically installed by humans at the plant. Robots mostly do welding and material handling. There are some "nut-runners" that put nuts on studs but bolts like this are usually installed by a human.
I work for one of Tesla's robotic suppliers for the body shop, so I don't know all of the details of final assembly. Just giving my two cents.

 

[ricardo_1]

Yes, mine broke up as wind pushed it down and started dragging on the road. I ripped the remaining part with my hand since it was making noise. Some of the bolts where loose and some fell out all together. The material can be ripped by hand. It is not that strong but mine broke probably because the screws became loose.
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This this happen to me. Took delivery of my model 3 a few days ago and noticed a gap where the bumper panel meets the wheel well on both sides. Scheduled an appointment to get it fixed, thought it was just a panel alignment issue, then on my way home today doing around 65 mph, I see a driver along side me pointing at something on my car. Initially I thought maybe my trunk popped open or something so I pulled over to check the car, had no idea what the issue was until I looked under the rear bumper. The middle part of the undercarriage was hanging down, all scuffed up, and no bolts holding it Basically acting like a sail, which was pulling the bumper. Anyway, I’m pretty lucky the entire bumper didn’t rip off completely. Now the fun part begins...after several calls to schedule an apointment who knows how long it will take or how Tesla will fix it. I understand these things happen, but as a new owner I’m not very impressed so far. Seems like a severe quality control problem and the bumper is just one of several issues I’m having after only three days.

 

[AlanSubie4Life]

This this happen to me. Took delivery of my model 3 a few days ago and noticed a gap where the bumper panel meets the wheel well on both sides. Scheduled an appointment to get it fixed, thought it was just a panel alignment issue, then on my way home today doing around 65 mph, I see a driver along side me pointing at something on my car. Initially I thought maybe my trunk popped open or something so I pulled over to check the car, had no idea what the issue was until I looked under the rear bumper. The middle part of the undercarriage was hanging down, all scuffed up, and no bolts holding it Basically acting like a sail, which was pulling the bumper. Anyway, I’m pretty lucky the entire bumper didn’t rip off completely. Now the fun part begins...after several calls to schedule an apointment who knows how long it will take or how Tesla will fix it. I understand these things happen, but as a new owner I’m not very impressed so far. Seems like a severe quality control problem and the bumper is just one of several issues I’m having after only three days.

Pictures, in particular showing how many of the bolts you still have intact, would be helpful. Unclear whether you are talking about the rear diffuser or the Mid Aero Performance cover (sounds like the diffuser to me as a loose aero cover would not be visible as a "panel gap").

I would just have Tesla come out and give you some new bolts to secure things (sounds like you need at least 5 bolts) and have them put a new part on order. Hopefully the bumper cover is not damaged (the diffuser and the bumper cover are two different parts).

EDIT: Also, what is the build date of your vehicle? On the upside, the rear bracket welds didn't fail!

 

[ricardo_1]

Pictures, in particular showing how many of the bolts you still have intact, would be helpful. Unclear whether you are talking about the rear diffuser or the Mid Aero Performance cover (sounds like the diffuser to me as a loose aero cover would not be visible as a "panel gap").

I would just have Tesla come out and give you some new bolts to secure things (sounds like you need at least 5 bolts) and have them put a new part on order. Hopefully the bumper cover is not damaged (the diffuser and the bumper cover are two different parts).

EDIT: Also, what is the build date of your vehicle? On the upside, the rear bracket welds didn't fail!

Build date was December, 2018. Here’s a few pics. Not sure how many bolts it’s supposed to have. I also noticed some strange round marks on the underside on left and right sides where it wraps under the bumper, not sure what those are from.

 

[ChrisH]

Ummmm wow. Why is all of that exposed?!