Dumb to not have it on the car. That's a Grade-A serious piece to remain ON the car as it came from the factory. Tons of serious engineering reasons to leave it on that we've gotten into over the years here and on many other forums. I'll let the smart group (a very very small group) explain it if they want. But taking it off and leaving it off is as dumb as it gets. Now that you know, put it back on.

 

I don't know if anyone would fess up to it if they did.

It protects that part of the engine bay, improves aerodynamics and helps manage airflow through the radiator.

If you want to track leaks, just remove it at night and slide a piece of cardboard under the front of the car. :dunno: It comes off in like 30 seconds.

 

It protects that part of the engine bay, improves aerodynamics and helps manage airflow through the radiator.

All true.

A very stupid piece to remove from the car, for all the reasons that have been outlined already.

I left mine off for a week while I monitored a leak. Do you need it off any longer than that? Just leave it off for a few days, and put it back on.

 

OnTheCar

 

7 one-turn Phillips and 3 expanding rivets is not what I'd consider a hindrance to access. Why do you "really hate it?" Do you find yourself driving to work in the morning, just fuming that the underpanel is hangin' on down there doing who knows what?

At the end of the day, it's your car. I don't think you're going to get a lot of support from folks here because there's really no benefit and there are tangible downsides, but you don't need the approval of a poll of strangers on an internet forum.

 

left all of them off after I swapped the engine. I didn't like that it hides leaks. perhaps people would be quicker to notice coolant or oil leaks if it didn't collect in the cover.

 

On the XI it helps protect the inner front CV boots.

I don't know if anyone would fess up to it if they did.

It protects that part of the engine bay, improves aerodynamics and helps manage airflow through the radiator.

If you want to track leaks, just remove it at night and slide a piece of cardboard under the front of the car. :dunno: It comes off in like 30 seconds.

^ this

It also keeps things from getting covered with sh!t.

Man, I'm in the wrong line of work. :rofl:

Good lord 65 bucks for 30 seconds? Sign me up.

 

Not going to call anybody dumb for not having it on. I have a friend with 2 e46's and an e39 and all of them were missing the pans when he got them. The cars haven't blown up or anything for the years he and his daughters have been driving them. I don't think it would hurt to drive without them for a while so you can track down a leak.

That being said, they serve a purpose and there's no reason to permanently remove them. The certainly help clean up the airflow under the car, offer some splash protection for the underhood electricals, and most likely assist with cooling air flow.

 

A good splash pan, like these cars have, also protects the engine and its accessories from hard objects--rocks, sticks, etc--as well. The XI part even has a special vent to cool the transfer case.

 

It's always seemed funny to me that before some point in the 1980s, no cars had those "shields". And then - suddenly - all cars had them. This leads me to believe that it's main purpose is to create some kind of aerodynamic "footprint" for each model car which is probably used for EPA mileage ratings, although, I have no research or data to backup my theory. It's just a wild guess as to it's purpose. If my wild guess is correct, I don't think it matters one way or another to the car owner as to whether it's on there because it certainly isn't much of a "shield". That's only my opinion though.

 

Before some point in the 80s, most cars didn't have catalytic convertors or oxygen sensors. They used Freon, which was highly destructive the ozone layer. They consumed a ton of gas and had poor performance. They used leaded gasoline, which has been shown to be one of the most destructive environmental screw ups we've ever been responsible for, with a good deal of data showing that the lead ban was responsible for the massive crime drop in the US. ( https://en.wikipedia.org/wiki/Crime_in_the_United_States#Crime_over_time ) People thought Genesis and Def Leppard made good music.

 

The skid plate actually serves as part of the cooling system, forcing air through the radiator and out the bottom of the car. Most cars should be fine without it and won't notice any issues but it does aid in cooling. If your climate is pretty hot I would definitely leave it on. The tray is particularly important at idle when the fan is on to direct airflow through the engine.

If you are trying to track down leaks I would suggest to do a steam clean of the engine first then monitor for wet spots. With the tray off all you'll notice is some drips on the ground and you'll still need to trace them back to their source. If it's something like the OFHG then it may take a long while to actually work its way down and onto the ground.

<-- Calibration Engineer for an OEM

 

Sometimes I wonder why not all manufacturers don't have that skid plate? Mine is on 100% of the times.

 

I only leave it off when i go for a test drive, then back to garage to inspect it when it is hot. Then allways put it back on without excuses. I think it is done in under 1 minute...

 

I like to keep the undercarriage of my cars protected. The only time I keep the shield off is when I am tracking down a leak.

 

It's good to see such an OEM kind of vibe here. I am on OEM kind of guy.

The repeated use of the word "stupid" is a bit excessive and seems wildly dogmatic.
It's stupid to drain all your oil and then drive your car down the highway.
It's stupid to polish your car with brake fluid.
It's stupid to destroy the OEM suspension of your car with slamming and camber and cutting your springs.

First off, it's not a "skid plate". It's a piece of plastic.
Can anyone actually describe a scenario which do you think this plastic is protecting you from?

No, it has absolutely nothing to do with cooling.
Proof? Take it off and your car will run at the exame same temp. Science!
The cooling air is routed through the front grills, wham, directly through the radiator.
How exactly does a panel under your car route air for cooling?

The reality? Aerodynamics. It may help with MPG and wind noise level.
It may even be to hide leaks as a form of planned obsolescence.

I will be leaving it off for a few weeks and I do not expect my car to explode into a ball of flames.
I have driven my E39 for 50k miles (along with countless others) for many years with no cover
with no ill effect except getting some dust up into the engine bay.

 

The repeated use of the word "stupid" is a bit excessive and seems wildly reactionary.

Agreed.

But, it's good to see such an OEM kind of vibe here.
I am on OEM kind of guy.

It's not a question of "OEM vs. aftermarket." AFAIK there are no aftermarket splash guards. It's just a matter of leaving a piece of the car in place b/c there are good reasons to do so.

First off, it's not a "skid plate". It's a piece of plastic.
Can anyone actually describe a scenario which do you think this plastic is protecting you from?

Water splashing up and fouling low-hanging electrics like the alternator, stones impacting power steering lines, serpentine belt, etc.

No, it has absolutely nothing to do with cooling. Proof? Take it off and your car will run at the exame same temp. Science!

The needle may remain in the same position, but have you actually recorded the coolant temp using the OBC readout with the shield on and off?

The cooling air is routed through the front grills, wham, directly onto the radiator.
I can't even understand hw someone can think it has to do with cooling.
How exactly does a panel under your car route air for cooling?

It's not that intuitive. The nose of the car has regions of high and low pressure. With the splash guard removed, a low-pressure area is created under the engine bay, which pulls air in through that opening that would otherwise go through the high-pressure area in front of the radiator. Air follows the path of least resistance.

I will be leaving it off for a few weeks and I do not expect my car to explode into a ball of flames.

Strawman.

 

I drove without that pan for months because the spring clips that the screws attach to were all either broken or missing. Apparently it's not a critical part. Is it a good idea to have it? Certainly. Will anything catastrophic happen if it is not attached? No.

 

Water splashing up and fouling low-hanging electrics like the alternator, stones impacting power steering lines, serpentine belt, etc.


When you drive through a large puddle, are are moving forward, the wheels cause the splash.
Pay careful attention where the wheels are located. They are behind the engine, and the car is moving forward.
What sort of physics do you think makes the JFK magic water go forward and then back upwards into the front of the car?

 

And where do you think the water moves from the tires???

 

But, it's good to see such an OEM kind of vibe here.
I am on OEM kind of guy.

It's not a question of "OEM vs. aftermarket." AFAIK there are no aftermarket splash guards. It's just a matter of leaving a piece of the car in place b/c there are good reasons to do so.

Not sure if you're just trying to be difficult, or if you truly were unable to comprehend the sentiment being expressed in my sentence.

 

The needle may remain in the same position, but have you actually recorded the coolant temp using the OBC readout with the shield on and off?


Yep.
OBC test. Test 19/test 7
96C before and after

 

The belly pan protects hoses, pulleys, electrical connections and other parts. I think that those that don't install it are the ones that take the start out of the trunk.

 

opcorn:

 

A few thoughts:

1) I like threads in which the question asked did not result in the desired answer, so people get #madonline
2) As someone who has spent a career in consumer goods, companies do not add parts to their product for fun - especially high-cost parts like a large plastic panel that costs a significant amount to manufacture and a significant amount to transport and store during manufacturing. There is a reason it is there. It was included by the factory for a purpose, whether that was weather shielding, air ducting, mpg, some sort of legal/regulatory compliance or even evil corporate skulduggery as you suggest.

Will your vehicle "catch on fire" without it? Of course not. If your car didn't come with one because the PO lost it, do you need to go pick one up from the dealer before driving it home? No. If you have one already should you leave it installed long-term? Yeah, probably, since it costs you nothing except 3 minutes of removal time when you need to work under the vehicle. Heck, if it saves you 1/4 mpg (which is within the realm of possibility), it's worth having it installed for the long haul. Keeping it permanently uninstalled because you "hate it" is just kinda strange.
3) To the folks who suggest leaving it off permanently to "detect leaks more easily," how frequently do you get fluid leaks? Personally I think regularly checking fluid levels and crawling under when something is low is a pretty easy way to detect leaks, but I suppose that's neither here nor there.

This is a really silly debate - do what you want. If you don't want answers, there's no reason to post questions. Especially on topics that have already been discussed ad nauseum on this forum.

 

:facepalm:

Spannerhead got it quite right.

The pan helps maintain a pressure differential across the radiator. When you remove the pan, more air flows up behind the radiator, reducing the pressure differential, and reducing the flow through the radiator.

With a well maintained car in normal conditions, it probably isn't going to cause a serious issue. However, these cars have somewhat sensitive cooling systems. Far too many have had overheating issues. Why invite trouble?

Don't be stupid or lazy. Put the pan on.

You're a big boy. You can make your own decisions. BUT, if you're going to ask questions, ignore good advice (and even take an attitude towards it), you'll start being ignored or ridiculed. And you'll wonder why. If you're offered good advice, I'd recommend you take it.

 

Another often overlooked part is that the belly pan restricts airflow out of the bottom, which encourages more to go up top between the hood and the cowl. Without the pan you're just allowing more pressure to buildup under the front axle

 

I bought my 2006 330Ci used and it did not have the belly pan. By coincidence, I was at the dealer yesterday and the mechanic said that it was missing and for $175 (part) and $65 (labor) they could replace it.
If I had one in decent shape, it would be on. I wouldn't pay $100 for it as offered by ecstuning.

 

for ... $65 (labor) they could replace it.

Man, I'm in the wrong line of work. :rofl:

 

I zip tied mine after running into a few rocks.

Doesn't help that over the years, I've "lost" my front inner liners, front brake ducts, pretty much anything remotely close to the bottom front end of the car has disappeared lol. Even one of the aux temp sensors for HVAC... Ugh

 

Doesn't help that over the years, I've "lost" my front inner liners, front brake ducts, pretty much anything remotely close to the bottom front end of the car has disappeared lol. Even one of the aux temp sensors for HVAC... Ugh

What kind of roads are you driving on? :rofl:

 

Mechanics at dealerships probably religiously re-install them. Mechanics at Joe Bob's Garage more than likely toss them as "non-essential" parts. A lot of mechanics (a loosely used term) will leave off a lot of clips, brackets, connectors, bolts, etc. that are not absolutely needed to keep something from falling off. That doesn't mean that the part serves no purpose, it just means that it's more trouble to put it back than somebody wants to take.

Leaving it off for a while when you track down a problem won't hurt a thing. No reason to keep it off once that is done, especially since doing that will either have you throwing it away, or storing it. No better place to store it than under the car. It really is simple to take off and re-install.

 

Leaving it off for a while when you track down a problem won't hurt a thing. No reason to keep it off once that is done, especially since doing that will either have you throwing it away, or storing it. No better place to store it than under the car. It really is simple to take off and re-install.

Well said. There's no better place to store it than on the car. However, I am not freaking out while it's off for a few weeks.

 

My E46 was missing the belly pan when purchased, it was an abused car I picked up to restore for DD use. I have monitored coolant temperatures and have not seen any change in normal behavior, even in 100+ degree weather we have here in Sacramento. I also daily drive this car 5 days a week 50 miles daily. I don't like taking my weekend car out in the rain, so I use this car. After a long drive in the rain, when I open up the hood there is absolutely no water splashed onto the upper parts of the engine.

That said, the pan does help with aerodynamics, and in some radiator designs, with airflow. The pan is rear of our radiator, and the pressure differential is not significant enough to cause problems. I had an RX-8 with a 45 degree mounted radiator. The pan was essential to provide proper airflow. Our cars...not so much. But thats just my opinion as a mechanical engineer. If you have the pan, I don't see why you would remove it. But if it's missing, don't loose sleep over it.

 

I leave mine on and would pay the $100 to replace it if it was lost or missing for some reason.