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Ok to take off my undercarriage plastic cover?

aphex

aphex

Moderator<br>All Things Apple
Moderator
As my 2005 Mazda3 is now rounding 150k miles, the plastic cover under the car is beyond wrecked (hanging down in places, all discombobulated)

Anything wrong with just taking it off and leaving it off?
 
Most of the undercarriage covers are to either protect something from debris or to help with airflow to improve mpg. If you're really worried just buy a new one.
 
The plastic undertray is long gone from both my 951 and my S70. They just got in the way of working on the cars. Supposedly they helped with airflow, but I've seen no increase in engine temps nor any issues with wind noise or mileage.

On the other hand, replacing it probably won't be a big deal.

ZV
 
The one on my van keeps water off my belts which makes them slip. The one on my miata helps air flow through the radiator and keeps some of the dirt out of the engine bay. It is hanging on the wall of my garage because it gets in my way when I'm working on crap. Also see no difference in engine temps and the engine is already filthy from oil leaks.

Take it off. It won't make your car explode.
 
SpatiallyAware said:
Replace it. Often times it 'looks' ok (engine temps etc) but after 30-40k miles your engine bay looks like crap
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Oh noes! My engine might get a little dirty! The horror! 🙄

Millions and millions of cars that never came with plastic trays even from the factory manage just fine.

ZV
 
Zenmervolt said:
Millions and millions of cars that never came with plastic trays even from the factory manage just fine.

ZV
Click to expand...

The cars without one weren't designed to have one installed. I'm just hesitant to remove anything from the car that engineers spent time and money developing. In the quest for profits couldn't the manufacturer just excluded the part?

My wife's S40 has the tray. While it's a bit of a pain, it's got a couple of air scoop looking things on it so it stays.
 
Replace it. And who knows, maybe someone makes an upgraded one? I replaced my plastic one with an aluminum one. Others who have done it reported engine temps dropping also.
 
franksta said:
The cars without one weren't designed to have one installed. I'm just hesitant to remove anything from the car that engineers spent time and money developing. In the quest for profits couldn't the manufacturer just excluded the part?

My wife's S40 has the tray. While it's a bit of a pain, it's got a couple of air scoop looking things on it so it stays.
Click to expand...


Not really designed persay. A large reason for them, at least some, was to catch any fluids. Many cars had such a bad oil filter placements that oil would drip even after service. Let alone small leaks might not be noticed till after warranty. etc...

I would replace myself, check dealer then junk yard. But I would not worry to much if it was taken off.
 
Zenmervolt said:
Oh noes! My engine might get a little dirty! The horror! 🙄

Millions and millions of cars that never came with plastic trays even from the factory manage just fine.

ZV
Click to expand...



No need to be a d-bag.


It's a legitimate problem.. Sand/dirt builds up in crevices and holds moisture, can cause connectors to corrode and etc. I've seen 15-20 year engine bays that were a PITA to work on just from the junk built up over the years.

They're usually $20-$40, definitely worth replacing.
 
SpatiallyAware said:
No need to be a d-bag.


It's a legitimate problem.. Sand/dirt builds up in crevices and holds moisture, can cause connectors to corrode and etc. I've seen 15-20 year engine bays that were a PITA to work on just from the junk built up over the years.

They're usually $20-$40, definitely worth replacing.
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15-20 years? Hose off the engine bay every few years, then.

And try working on anything that's seen more than three NH winters. 😛
 
jlee said:
15-20 years? Hose off the engine bay every few years, then.

And try working on anything that's seen more than three NH winters. 😛
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Hose off the engine bay every few years... Are you joking?


How about spend $20 on the piece of plastic designed to help airflow, catch fluids, prevent dust/dirt/rocks from getting sucked into the engine bay.. Car man'f will do whatever they can to save a few pennies, if that was a totally useless part they'd have left it off.
 
SpatiallyAware said:
Hose off the engine bay every few years... Are you joking?


How about spend $20 on the piece of plastic designed to help airflow, catch fluids, prevent dust/dirt/rocks from getting sucked into the engine bay.. Car man'f will do whatever they can to save a few pennies, if that was a totally useless part they'd have left it off.
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You care what your engine looks like but you don't ever clean it?
 
jlee said:
You care what your engine looks like but you don't ever clean it?
Click to expand...


It's not so much an issue of looks, it's an issue of not wanting sand/crud/dirt all in the engine bay.


You and ZV obviously don't care - but the OP wanted to know if there's anything wrong with leaving it off.. It does make a difference. You might not notice it in 6-7 months but give it a year or so and it'll be noticeable.
 
jlee said:
I guess we're running on two different wavelengths here. 😛

Yes, it's going to make a difference. I highly doubt it's going to hurt anything, though.
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I like the tray because when I'm working under my car (04' civic coupe STOCK) I take the tray off and I don't have to knock junk off of stuff. In my old car 94' Nissan Altima had every thing under there covered with i dont even know what!
 
On many cars, it was added to improve a/c and radiator performance when the vehicle is stopped and idling. Without the cover, the heated air coming out of the back side of the radiator/condenser module can easily get pulled forward and sent back through, which is not desirable and reduces the efficiency of the heat exchangers. Again, this recirculation only occurs when the vehicle is not moving. You wouldn't see any change in performance when the vehicle is moving.

On other cars, they are used to prevent splashing of water on certain electronic components or on the electric cooling fan motor itself.

And on some cars they might be used as an underbody aerodynamic device intended to clean up the airflow underneath the vehicle. Many European manufacturers use this design technique.
 
SpatiallyAware said:
You and ZV obviously don't care - but the OP wanted to know if there's anything wrong with leaving it off.. It does make a difference. You might not notice it in 6-7 months but give it a year or so and it'll be noticeable.
Click to expand...

Yeah, the fact that there's no buildup in any of the cars I've removed it from is clearly just me not caring. 🙄

Unless you're going off-roading or ploughing through sandy beaches there just isn't going to be enough junk getting into the engine bay to be any sort of problem at all. Period. End of story. The 951 has been missing its plastic tray for at least a decade now and it still looks clean underneath. The Volvo for maybe only half that, but, just like with the 951, still looks perfectly clean underneath.

Most of the time they are there for noise control or, as Marlin said, to catch fluids so owners don't notice insignificant leaks and panic. If you're running track days at 100+ mph then any airflow changes they make might be noticeable, but on the street it just plain doesn't matter. Hell, I don't know a single 944 owner who still has the undertray on their car and I've never heard of any problems at all because of it.

The simple reality is that for street cars an undertray just plain doesn't make any meaningful difference. If someone wants to replace it because the $20-$100 is worth the piece of mind, that's fine, but driving without an undertray won't hurt a goddamn thing.

ZV
 
Old topic but yeah, I was thinking on doing the same. It's easier to perform some service, especially on car models where oil filter is hidden way beneath it all, typically on V engines. Some say aerodynamics are compromised badly from removing the splash tray, but just as many people say this is pretty much b/s and that the average Joe couldn't tell a difference.
 
I have a Suburu Impreza. The plastic tray below the car is quite large, almost looks like a skid plate, but is only plastic.
I find it is useful in deep snow to help prevent the snow packing around the control arms and other underbody areas.
 
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^also prevents the exhaust manifold from being exposed to any road spray traveling under the car, to some degree.

I just recently had to re-tap the bolt holes for the plastic cover on my Impreza--which proves that it does see its fair share of weather; the bolts were very rusted and needed to be drilled out. I'm pretty confident that without that tray there on my car I would've had to replace the header and upstream catalytic converter (plus probably both O2 sensors) and that's an expensive piece.
 
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