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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 12-09-2011, 01:01 PM
black540eye black540eye is offline
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Removal of plastic cover under engine?

Hi,

Well, it looks like I have a slight coolant leak. I did a complete cooling system overhaul about 2.yrs ago (38K miles ago). In order to really see where the leak is, I was wondering if there would be any ill affects of removing the plastic cover piece that is under the engine and drive it a few days that way..or at least until I get parts to repair whatever is leaking, etc. I wasn't sure if it would drastically affect the engine cooling process by removing that piece....or is the piece just to keep dirt/grime/etc from coming up underneath, etc.

Thanks.
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  #2  
Old 12-09-2011, 01:25 PM
WaveSurfin3100 WaveSurfin3100 is offline
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If you remove it, you are leaving yourself open to possibly damaging critical components you expose by removing that bottom engine cover! If by bad luck you happen to run over say a piece of lumber, a hubcap, or just about anything that falls off a truck or someone elses vehicle, it may kick up and do some extensive damage to say your oilpan, steering pump..etc. Risky, but it's your call. Why roll the dice when it takes just a few minutes to remove said item when you are ready to start wrenching. Good Luck!
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  #3  
Old 12-09-2011, 01:30 PM
BigPat3472 BigPat3472 is offline
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I dont see much harm in it... but they did put it there for a reason.... midas well keep it there... although 85% of the cars in the road dont have them........ your call

Sent from my DROID BIONIC using Bimmer
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  #4  
Old 12-09-2011, 02:07 PM
black540eye black540eye is offline
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OK...sounds like it won't affect the cooling of the engine per say...just more of a protective measure. I need to take it off to see what is leaking...once off, I was just going to leave it off until I start wrenching..put it back on when all is good...But it may be a week or two between the two

Thanks
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  #5  
Old 12-09-2011, 02:49 PM
windsmith windsmith is offline
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Quote:
Originally Posted by WaveSurfin3100 View Post
If by bad luck you happen to run over say a piece of lumber, a hubcap, or just about anything that falls off a truck or someone elses vehicle, it may kick up and do some extensive damage to say your oilpan, steering pump..etc.
Right, because a flimsy plastic cover will keep high velocity lumber or pieces of metal from damaging anything that's behind it.

But seriously, my 540iT didn't have one when I bought it. I may buy one to put under there, but only because I feel that it may help with reducing under-car drag on airflow and improving fuel economy.
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  #6  
Old 12-09-2011, 02:49 PM
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the540wgn the540wgn is offline
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Quote:
Originally Posted by black540eye View Post
OK...sounds like it won't affect the cooling of the engine per say...just more of a protective measure. I need to take it off to see what is leaking...once off, I was just going to leave it off until I start wrenching..put it back on when all is good...But it may be a week or two between the two

Thanks
Just checkin, you're talking about this piece right? (or similar)
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  #7  
Old 12-09-2011, 04:15 PM
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Nline6 Nline6 is offline
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Its a splash guard. So as long as its not raining?? LOL jk. I think you would be fine. I removed mine for that exact reason. Its hard to spot a leak when it funnels down the splash guard. Just watch out for debris in the road.
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  #8  
Old 12-09-2011, 09:32 PM
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Mine has been off ever since I did my cooling system.

That was, oh, um ... maybe about two years ago.
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  #9  
Old 12-10-2011, 05:24 AM
windsmith windsmith is offline
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Bluebee, did you notice any change in fuel economy following its removal? (I am fairly certain that you track this)
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  #10  
Old 12-10-2011, 05:41 AM
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The purpose of that cover is more to improve aerodynamic efficiency than to protect components (as noted, most cars do not have this pan and plastic will not provide much protection). It is HIGHLY doubtful that anyone would notice any difference in gas mileage or top end by removing that component. One has to understand that, from an engineering standpoint, improvements in vehicle gas mileage and/or top end are achieved by small incremental improvements across multiple areas (weight reduction, improved aerodynamics, greater engine efficiency, etc.). Combining many small incremental improvements in these areas yields a measurable improvement to the overall system efficiency. Conversely, elminating an improvement to one subsystem will not yield a noticeable difference.

Bottom line, you can drive without it and you will notice no differences in gas mileage or performance.
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  #11  
Old 12-10-2011, 05:48 AM
windsmith windsmith is offline
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Quote:
Originally Posted by Fudman View Post

Bottom line, you can drive without it and you will notice no differences in gas mileage or performance.
This is good theory, but I wanted some input from actual 'tests' if you will.

Aerodynamic drag is the single most important factor affecting highway fuel economy (after accounting for any elevation changes), therefore any change in aerodynamics of the vehicle will be noticeable.

You see those skirts popping up on the undersides of over-the-road truck trailers? They improve fuel economy of the trucks by 0.5mpg. Considering that they average 6mpg, that's almost a 10% improvement, just from a minor aerodynamics change.

Besides, Bluebee notices (and then checks, tests, re-tests, files, categorizes, organizes and links) things that most of us will never think about.
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  #12  
Old 12-10-2011, 05:49 AM
JimLev JimLev is offline
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+1....Listen to Fudman. Most cars don't have them.
If a piece of lumber flew up it would most likely rip the plastic to pieces before it would damage a metal oil pan.
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  #13  
Old 12-10-2011, 05:51 AM
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dalekressin dalekressin is offline
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yep, mine is in the garage too since the cooling & Vanos jobs were completed. No Problems yet.
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  #14  
Old 12-10-2011, 07:42 AM
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Quote:
Originally Posted by windsmith View Post
This is good theory, but I wanted some input from actual 'tests' if you will.

Aerodynamic drag is the single most important factor affecting highway fuel economy (after accounting for any elevation changes), therefore any change in aerodynamics of the vehicle will be noticeable.

You see those skirts popping up on the undersides of over-the-road truck trailers? They improve fuel economy of the trucks by 0.5mpg. Considering that they average 6mpg, that's almost a 10% improvement, just from a minor aerodynamics change.

Besides, Bluebee notices (and then checks, tests, re-tests, files, categorizes, organizes and links) things that most of us will never think about.

I get what you're saying. However, true "testing" is only valid when you can control the variables and can reproduce your results. The "testing" done by members of this forum is more on the level of simple observation.

The side skirts you mention are a significant improvement to reducing turbulence and drag on a tractor trailer because the initial Cd of a tractor trailer is in the range of 0.90. The Cd on an e39 is about 0.30. Removing the pan would not change that value.

FWIW, I did a 700 mile R/T without my pan (after changing my ATF) and noticed no difference (about 29-30 mpg). Was that due to the ATF change or lack of a pan? Who knows? Bottom line is that anyone who tells you they can notice any difference (plus or minus) due to this change does not know what they are talking about or is severely deluded.
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  #15  
Old 12-10-2011, 10:07 AM
nsogiba nsogiba is offline
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Took it off when i did my radiator a few thousand miles ago. No harm at all leaving it off!
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  #16  
Old 12-10-2011, 02:34 PM
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Trebbia Trebbia is offline
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It won't affect gas mileage that you can measure.

It won't affect noise that you can measure.

No test with home equipment is going to notice anything different unless you already wanted it to aka butt dyno.
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  #17  
Old 12-10-2011, 03:24 PM
uncmozo uncmozo is offline
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Quote:
Originally Posted by Fudman View Post
The purpose of that cover is more to improve aerodynamic efficiency than to protect components (as noted, most cars do not have this pan and plastic will not provide much protection). It is HIGHLY doubtful that anyone would notice any difference in gas mileage or top end by removing that component. One has to understand that, from an engineering standpoint, improvements in vehicle gas mileage and/or top end are achieved by small incremental improvements across multiple areas (weight reduction, improved aerodynamics, greater engine efficiency, etc.). Combining many small incremental improvements in these areas yields a measurable improvement to the overall system efficiency. Conversely, elminating an improvement to one subsystem will not yield a noticeable difference.

Bottom line, you can drive without it and you will notice no differences in gas mileage or performance.
Well said!
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  #18  
Old 12-11-2011, 07:40 AM
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bluebee bluebee is offline
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Quote:
Originally Posted by windsmith View Post
Bluebee, did you notice any change in fuel economy following its removal?
Given the 1mpg tolerance of our MPG calculations:
- What is the tolerance (i.e., accuracy) of our typical miles per gallon (MPG) calculations (1)

There would be no way we could accurately measure any difference, even if we wanted to.

So, 'no', I didn't notice anything different in miles per gallon with the bottom plate off the vehicle.
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  #19  
Old 12-11-2011, 08:24 AM
promojax promojax is offline
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coolant leak

Quote:
Originally Posted by black540eye View Post
Hi,

Well, it looks like I have a slight coolant leak. I did a complete cooling system overhaul about 2.yrs ago (38K miles ago). In order to really see where the leak is, I was wondering if there would be any ill affects of removing the plastic cover piece that is under the engine and drive it a few days that way..or at least until I get parts to repair whatever is leaking, etc. I wasn't sure if it would drastically affect the engine cooling process by removing that piece....or is the piece just to keep dirt/grime/etc from coming up underneath, etc.

Thanks.

Look to see if your coolant leak is fron the thermostat housing it will drip. Had this problem and that was were the leak was and it was hard to find. Also get a coolant system
pressure test done that will help
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  #20  
Old 01-10-2012, 11:06 PM
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bluebee bluebee is offline
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For the cross-linked record, this was asked just now:
- E39 (1997 - 2003) > Bottom engine cover

Quote:
Originally Posted by Ninety-8 E3nine View Post
Does anyone drive their car without the bottom engine cover? What kind of risks are there? Does anyone have bad experience?
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  #21  
Old 01-10-2012, 11:09 PM
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bluebee bluebee is offline
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So that the next person finds this easier, I just added a keyword-rich sentence pointing to this thread in the bestlinks:

- What happens if you remove the under engine cover splash guard plastic shield (1)
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  #22  
Old 01-11-2012, 08:46 AM
5 BMW's 5 BMW's is offline
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Bluebee, I think I LOVE you! You are truly the most amazing source of information for my beloved E39!
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  #23  
Old 09-18-2013, 12:07 PM
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bluebee bluebee is offline
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Here is another question about the engine splash guard, posted today:
Quote:
Originally Posted by lacanadio View Post
Front underneath engine cover had worked loose of the spoiler and was hanging down. Need to do some rebuilding there...
Bob
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Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #24  
Old 09-18-2013, 04:00 PM
juststeve juststeve is offline
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One of the 39s I purchased was missing the splash shield when it arrived in the driveway. I noticed more road noise with out it in place so I spent the $80-$100 on a new one.

Keep in mind there is other road debris just as damaging as a 2x4. Water, coat hangers, plastic bags even large or small hunks of truck tire can end up wrapped around a drive belt. That panel is cheap insurance...
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  #25  
Old 09-19-2013, 01:56 AM
HTK12 HTK12 is offline
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Quote:
Originally Posted by juststeve View Post
One of the 39s I purchased was missing the splash shield when it arrived in the driveway. I noticed more road noise with out it in place so I spent the $80-$100 on a new one.

Keep in mind there is other road debris just as damaging as a 2x4. Water, coat hangers, plastic bags even large or small hunks of truck tire can end up wrapped around a drive belt. That panel is cheap insurance...
If your serious about protecting the engine bay get a real skid plate. That splash shield offers only very limited protection. Large piece of truck tire will go right through that splash shield. I wouldn't trust it to stop anything that is larger than 1" in diameter.
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