I’m willing to bet genuine, damp money that this has happened to you or someone very close to you at some point: on your car or one of your cars, likely one made in the past 20 years or so, you’ve noticed an annoying flapping sound or a scraping sound. It gets progressively worse and is louder and more annoying the faster you go. It’s awful, and by now I suspect you know exactly what it is: big hunks of plastic coming loose from under your car. These plastic sheets and panels are sometimes known as splash shields or aero shields or underbody shields, something like that. They’re also one of the worst-engineered components of modern cars and are a global embarrassment that so far no automaker seems remotely interested in doing anything about.
Years ago, I wrote about what I felt was one of the biggest engineering failures in the automotive world, the scourge of sagging and falling headliners that plagued cars from the 1970s to the 1990s. I think the industry-wide epidemic of falling splash guards easily meets or even exceeds the Great Headliner Failure of decades past; the problem crops up on cars all across the automotive spectrum, and doesn’t seem to be restricted to inexpensive cars. Premium cars seem as likely as any to have their underbody plastic sheeting tear and break loose, which gives the problem a nice egalitarian character, at least, as likely to plague Mercedes-Benzes as a Hyundai.
It’s probably worth mentioning just why these shields exist in the first place, and there’s a number of very valid and reasonable explanations. They provide some aerodynamic benefit, helping to smooth out the path of airflow under the car, they prevent water and dirt and grime and other crap from being flung up into the engine bay, where it could potentially cause electrical issues or increase wear on belts and hoses, and, well, I suppose that’s pretty much it. They provide some degree of protection from scrapes and bumps, but they’re not actual skidplates, so your oil pan may still be boned if you whack it hard on a rock, plastic shield or no.
I was going to provide some links to people talking about the issue of loose or falling plastic shields, but a bit of Googling soon revealed the folly of that idea, because there are so many examples. If you just type into Google the words “plastic cover under” – not even mentioning anything about a car – you get results like this:
Look what you get: loose, fell off, came off, hanging, dragging, the state of plastic covers under cars is not a good one.
I tried one with a normal browser window and one in incognito mode, just to be sure the suggestions weren’t influenced by my previous search history, and, as you can see, even without specifying car, Google knows what’s going on, because vast numbers of people have been asking these questions, since these stupid plastic shields have been tearing off cars all over the place.
The reasons why this happens isn’t exactly rocket surgery: the plastic gets worn and tears, especially around the points where the plastic shields actually attach to the structure of the car, where it’s usually secured with plastic clips and tabs and other bits of degradable, consumable hardware. Plus, many of these shields require removal to do basic maintenance like oil changes, and that increases wear and tear on the too-fragile fasteners that hold these things on.
They’re also usually a pain in the ass to get out of the way when you just want to change your oil, and I suspect many get ripped out in during these processes.
Tomorrow I’m supposed to help a friend remove one of these shields from her Honda Fit; it’s one I’ve repaired with zip ties before, and I can’t even recall just what number of times I’ve done exactly this same job – ripping out a raggedy splash shield – for one of my own cars or a friend’s car, often done with some amount of frustration and anger in a parking lot, at night.
If your car has these plastic shields, it’s not really a matter of if it’ll get torn and start flapping around, it’s a matter of when. These are not really a solved engineering problem, by any means. They all fail, and they all fail in essentially the same, annoying ways. The holes for the plastic fasteners rip, the panels themselves rip, everything sags and flaps and oh they’re just stupid and terrible and nobody likes them!
My older cars don’t have any of these things and they survive, somehow. And, I’ve yet to meet anyone who has yanked out big chunks of ragged charcoal-gray plastic from under their cars, flung it in a dumpster, and somehow regretted it. Once these things are ripped out, perhaps your highway fuel economy drops by half a mile per gallon, perhaps your belts get more wet than before, but generally, quality of life improves.
There have to be better ways to mount these things if they’re so important, but I doubt that will actually ever happen, because that would require more money to be spent. Fastener holes could be reinforced with metal grommets, or some manner of quick-release clamping system could be used to retain the splash guards, but is any carmaker going to invest more money to make that happen? I doubt it.
From their perspective, this is hardly a problem at all. The shields start to fail long after the car has been purchased (generally) and the customer either rips the floppy plastic out or pays to have a new sheet installed. The carmakers have no downside here! This is just one of those side effects of capitalism where making something not suck just isn’t worth it, and the consumer can just shut up and deal with it.
But that doesn’t mean we have to like it! We can kvetch, loudly and boldly, and let the automotive world know we’re on to them. Underbody plastic bullshit is garbage, piping hot, cream-frosted garbage, and we’re doomed for the foreseeable future to have our cars, at some unpredictable, unexpected time start to make horrible flapping noises, requiring us to shimmy under the car and sweatily cut and yank and grab and pull out all of that near-useless, degraded plastic, and fling it into the trash, angry at the waste and senselessness of it all.
So, I’m calling this as The Biggest Modern Automotive Embarrassment. Plastic splash guards and underbody shields may be engineered for their purpose, but it appears no attempt is made to consider the longevity of these things, or how they may fail. And the result is hassle for pretty much every car owner, at some point.
Screw these things. We can do better. I have to believe that, I just have to.
Oh, but it’s worse than that!
The splash shield is connected to the fender liner and connected to the splitter. (why the fuck does everybody need a splitter now?) And the splitter is out way ahead of the front tires and lower than curb height so that if you park at an angle or a parking lot with a little concrete things to keep you from going into the next parking space it tears the splitter off. And the split her tears the under tray splash shield off. And the under tray tears the fender liners out.
Now back in the before times that would’ve been fine, but now, in the now times, designers think to themselves “I’ve got this wire that goes sort of near the fender and I need to put this computer on it. Why not put it in the fender fender rather than the engine compartment since it’s all nice and cozy protected there because of all that plastic we’ve put in.
So inevitably, if you park diagonally near a curb or in a parking lot with those little things to tell you where the end of the parking spot is, and you have a modern car with all the crap underneath that you can’t tell where the front of the car is because Reasons, you end up with mud and wet leaves piled up on top of the computer thing in the fender .
I posit that this is a bad thing.
The splitter on my car pulled the grille out after several years. The splitter is now gone.
I need to have the Toyota dealer, reinstall all the stuff underneath my mother‘s Prius after I ran over a ladder on the freeway. Neither of the independent mechanics that I like want to touch it because they claim that none of the parts want to line up the first time you put them together, and I certainly believe them, but the Toyota dealer is not keen on me taking a sawsall to the replacement parts before they install them.
Sigh…
So I guess I’ll saw it off afterwards.
One of those tiny circular saws from harbor freight? Power shears?
My mechanic removed the splitter gratis. I’ve done business with him for years, and 4 other folks started going there because I sent them. It’s a terrific garage.
Every 2019ish F-150 has a rotting underbody shield barely hanging on.
And those shields aren’t even good plastic. They are fiber based: get them wet and they fall apart like paper mache.
The shield under my Sportwagen TDI has two screws that thread into the engine block itself. One of the heads broke off one screw flush with the block before I got the car, the other was also broken but I was able to force a couple threads of a bolt in to support one side, at least. It’s a little lopsided but every other screw is present and accounted for. Looks like they put some kind of insulation on it as well, a TDI thing since I haven’t seen it on gas VWs.
My fiancees Mazda3 has a great solution for oil changes without removing the pan. You undo two screws, and then you can rotate a small part of the cover out of the way. Right there is the oil filter and drain plug. Much better than pulling the whole damn thing like I have to do with the Sportwagen.
I have recently had to change serpentine belts (in both cases there were 2 belts) on two cars in the fleet. As usual on transverse engine vehicles a tire is removed then dreaded splash shields. On the Mazda the whole fender liner was one piece. I think dealing with the shield on/off took as much time if not more as the belts. On some corners and ends the thing is held on with screws, just use screws everywhere please! Much better than futzing with plastic fasteners. Added bonus, if the plastic hole wears a washer is the easiest fix. SOLVED!
I have an aluminum sheet one underneath my insight, made by an insight enthusiast. I noticed lean burn was easier to maintain after installing, but it does make oil changes more of a PITA. I think next time I’m going to cut a small access hole for the oil drain.
This has been a thing for over 40 years. Around 1980, or whenever VW put out the diesel Dasher, there was a full shield under the drivetrain to deaden the clatter of the dreaded oil burning diesel. Also around that time all Volvo 240s came with a plastic shield between the core support and suspension crossmember. After a heavy rain my customers would call about their power steering not working after going through water and I would suggest (again) that the shield they didn’t want to replace would fix the problem.
Did anyone else read that intro as FapFapFap…..suck so much?
Yeah, me either.
And combined with the pic featuring prominent, lurid taillights, it made me think “Oh good, Torch must be feeling better.”
You’re evil. Take my smiley.
These shields on Volkswagens for the last 25 or so years is why I couldn’t wait to splurge on a Mityvac oil extractor. I still occasionally pull the belly pan off my GTI or my Pacifica to drain the oil and hose off the pan in the driveway, but that is like every third oil change.
Maybe somebody could ask 1950s Citroën
https://i.imgur.com/sJKseDZ.png
My wife drives a VW that has a massive plastic shield that covers pretty much the entire front half, and has no little trapdoor/flap to access the oil pan drain plug.
That’s bad enough, but the 14 (14!!) fasteners are comprised of 3 different types: plastic push-in trim fasteners, some Torx, and some normal bolts. On the plus side, it turns what should be a one garage beer job into a three garage beer job with more colorful language. The day that car is out of warranty I will be making my own access hole with a sawzall.
The Audi one is just as terrible. It has a cutout to drain the oil but assumes it will drain straight down the middle of the opening. Nope! Once the oil starts dribbling around the edge of the opening it just splashes onto the cover instead of in the drain pan.
Want to do the job right? Remove the cover which consists of the 14 fasteners composed of three different types.
The standard oil change technique from the last 10 (20?) years has been to extract from the top w/ a pump – no need to touch the shield. I agree, however, an access hole would make sense
I smell aftermarket opportunity: carbon fiber options, extra rugged, various metal choices, color matching, graphics, aero-improvements… @weathertech
On my old car that undercover shared plastic rivets with the inner-fender-liner so every time I changed the oil I also had to detach/reattach the front of the fender liner. Well, eventually that wore out and ripped the mounting holes out and while the undercover never tore loose and started dragging guess what did tear loose and decide to wrap itself around my tire one night while going down the freeway.
Death to these things!
I see a lot of suggestions that these things be made out of metal – I believe my mother’s XTerra has (or had) a lot of metal pieces like that as standard equipment and the result is a billion endless rattles. We had as much of it removed as possible and it still rattles around at idle. It doesn’t excuse the bad engineering here, but imagine the wear and tear to the plastic happening on metal panels and the ensuing chorus that will make you think the bottom of your car was made by Zildjian.
Honestly, if it’s aero, could engineers work on flatter bottoms of the whole unibody?
Or lean into it and make these things disposable and out of more degradable material and cheap to replace?
Why am I even weighing in here? My newest car was made in 1993. If something’s going to hang down and drag on one of my cars, it’ll be the exhaust.
My Porsche has ones made of metal; the center guard is held in place by approximately 50 bolts that get corroded and rusty. Half my repair time is spent removing/replacing that thing!
The ribs and transmission tunnels in the floor of a monocoque are what give it stiffness, make the floor flat for aero and you lose rigidity, and now your brake, fuel and coolant hoses are inside your car under your seats and carpet, which is terrible for servicing.
Ha, I literally just changed one out for a friend last weekend.
You have plastic shields on your car? Lucky you! My Volvo’s is made out of some type of pressed paper-like substance that absorbs oil and water and disintegrates after time, especially if a crease is formed anywhere, like when you leave the last screw/plastic fastener at the front or back when removing the shield for an oil change and the loose end flops to the floor. The front end of the Volvo’s ripped off at the last oil change and Volvo wants fucking $150 for a new one!!! These things cannot cost more than $2 to make! Would it really be that much more expensive to make them out of the unbreakable comb plastic? That stuff would last longer than the cars they are installed on.
At least the wife’s Mazda CX-5 has the little access hatches for oil changes, so the full shield stays in place and wear is reduced.
My wife’s CMAX has one of those fiber bottom covers. I too, have looked at it and expected it to fail, although it hasn’t yet after eight years.
You hit the nail on the head though. that plastic would last roughly forever.
It’s not nearly as big a problem as,say, pop bottles since we don’t make nearly as many of them. Still,reducing use of non-recyclable parts Seems like a good goal.
Yep. I’ve replaced that cardboard crap under my Volvo twice now. I’d leave it off, but it does keep the engine bay somewhat less disgusting. Terrible material, terrible design. And it all has to come off to do an oil change if you do those from under the car. Jason’s right. This is a disgrace to the car world.
“… Volvo wants fucking $150 for a new one!!! These things cannot cost more than $2 to make!”
Call now to get your authentic new Nedre Motorkåpen for JUST $2!
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I know of a Volvo owner whose car was totaled after just a couple of years because a minuscule pebble went through the shield, and got caught in the timing belt. The entire engine was destroyed.
So don’t underestimate the importance of that shield.
Weird thing was the mk3 Focus changed from plastic to whatever fabric-like crap they went to. My ’12 SE was plastic, but the ’16 ST was the fabric-like crap. Wish I’d known, I’d have taken the plastic one from the totaled SE before it was hauled away.
Not something I’ve thought about in a while, but I did respond with a “hey yeah, those do suck!”. So validated right there. They’re also likely the #2 interstate trash item below tractor tires.
A lot of these aren’t even plastic anymore — they’re often some sort of fiber material to both quiet engine noise and reduce the chance of damage. Those are more susceptible to tearing, at the tradeoff of being way less likely to crack on impact.
I think a few reinforcements would do wonders at the attachment points.
Even dealer techs can’t be bothered to put all the fasteners back in these shields. When my 3rd CVT was dying under warranty, I was poking around and found that ~2/3 of the clips were never reinstalled from the previous CVT swaps. Fortunately I’m used to dealing with out of warranty shit boxes and had an assortment of clips available to replace the missing ones.
Kia didn’t bother to put the engine shield back on when replacing my engine.
I replaced the plastic one on my Mazda CX-5 with an aluminum one from CorkSport. It’s much more durable and the price was very fair.
I…misread that at first glance, but I’m glad to see I was mistaken.
No that was a silicone one.
Having one of these hanging down on the ground is the automotive equivalent to toilet paper dragging from your shoe.
And walking onto Air Force 1 with it stuck to your shoe.
Make it out of aluminum or stainless.
Maybe I’m naive or lucky, but I’ve owned several cars with a plastic undertray and have never had an issue with this. Even today, the undertray scrapes on my driveway, but it hasn’t failed. Admittedly I have purchased some used cars which had some of the fasteners missing, but I went to the effort of replacing those fasteners.
Your narrative here is that the plastic just tears or wears over time, but I’m not convinced of that. I’m willing to bet that the vast majority of torn/flopping undertrays are due to the tray hitting something (parking blocks are common) or someone being lazy and not replacing all of the fasteners during service, both of which fall under abuse or misuse that the undertray was never designed to survive. In other words, this is user error. Don’t run your car into shit or get lazy during an oil change and you probably won’t have a problem.
I would bet that most of these are people ripping them off on parking blocks or curbs. If not all of them. Even mediocre mechanics don’t want people coming back because their car is now making a scraping noise.
I keep a master kit of the plastic panel push pins in my garage. Always have to replace at least one when removing one for servicing. I’ve used a hose saw on one or 2 for easy oil filter and plug access.
Absolutely. This should be in everyone’s garage.
https://www.harborfreight.com/automotive-plastic-fastener-kit-240-piece-57671.html?_br_psugg_q=fastener
> I’ve used a hose saw on one
I know what you meant, but now I’m wondering what a hose saw would be. 🙂
Lorena Bobbit can answer that for you. Just ask John Bobbit.
Most parts on your car don’t require a wholesale replacement of all fasteners when you take it off for regular service. Kinda can’t blame people for trying to reuse the old clips.
They also break during normal, if harsh, driving. Gravel roads and heavy rain are well known for destroying these, especially the extra janky felt kind.
Well in my own experience I’ve been able to reuse every fastener I’ve taken off an undertray to remove it. The only time I’ve had to replace fasteners is when they were already missing. And admittedly gravel roads or heavy rain aren’t a factor for me, but YMMV.
I still mostly attribute this to laziness. Most of the time I’ve seen loose undertrays it’s due to missing fasteners, and as already stated plenty of times here, that’s usually due to lazy repair techs. When I bought my Mazda 3, literally half of the 10 fasteners for the undertray were missing. I replaced the missing fasteners and it’s been fine ever since.
You are all forgetting snow and water. Driving through either when they have built up is enough to rip the pressed paper shields, and possibly the plastic. I have to drive through either throughout the year, and I know that snow is the one that ripped 2 of my shields this last year. I can’t really avoid them and the fasteners didn’t fall out, the shield just ripped where it was attached.
As a Southern Californian, that admittedly didn’t cross my mind.
I once tore an OEM plastic wheel cover clean off driving through water! And their surface area is much smaller than the relative sail of a panel.
I agree. I’ve put well over a half million miles on cars with these underbody trays and I’ve never lost one. Once you get familiar with a specific vehicle, you can zip the fasteners on or off in about 5 minutes. I take them off road (not hard core) and through seriously deep snow. Whenever I see one of these things flapping in the wind, I generally assume the driver drove drunk over one of those concrete parking stops. Probably a bit harsh, but sometimes it’s fun to stereotype.
I’ve never lost one, but my Fords had cheesy plastic threaded inserts for the course-threaded bolts that never seemed to want to start straight. Were someone less careful, they’d be easy to strip out after a few uses. I did lose one of them to a giant ratchet strap buckle shed by a tractor trailer on the highway, but that’s understandable.
Don’t those plastic shields also (supposedly) improve engine cooling (when properly designed) by causing the airflow through the engine bay to go front to back instead of dumping down just behind the radiator which would cause stagnant airflow near the top of the engine?
yeah, I’m sure they do, sorta.
Also, your local mechanic may not really care or is pressed for time, so it might not have all the fasteners when it goes back on. This is worse then the Subaru exhaust heat shield rattle. You know, those turkey roaster trays they put above the cats. Those suck too.
My wife had a Mazda5 that I almost always handled the old changes on. It had one of those big shields. It was fine.
Then, my wife took it to an oil change place (not one of the big chains), and they apparently lost all the fasteners and just zip tied it in place. It ripped apart on the drive home and scared the crap out of her. The oil change place denied any responsibility and declared it was like that when it came in.
They’re out of business now.
I had a quick lube shop tell me they couldn’t do an oil change on my (then) brand new 2012 WRX because they couldn’t get the plastic shield odd “without a lift”
Took it to a dealer for that oil change instead and did all of the rest of the oil changes on that car myself…
My 2011 WRX had that same shield, it was a real pain in the ass to take off/on every time but I managed it with nothing but a pair of jack stands. You probably dodged a bullet, any shop that thought it required a lift would probably screw up the oil change too.