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7 Series - E38 (1995 - 2001)

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  #1  
Old 07-26-2015, 06:00 AM
TNe38S TNe38S is offline
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Location: Collierville, TN
 
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Mein Auto: 2001 740!
Engine belly pan traps a LOT of heat...no more pan for me

Since i have owned this car, i have not had one. Never really felt it too important to deal with (too many more pressing issues). Plus it might hide my oil leaks and we can't have that!

Anyway, while I was away on vacation, I left my car at the local BMW specialist to have some things taken care of while i didn't need the car.

disclaimer: I have the interval ii system so I can monitor the water temp closely and I have a modified cooler Tstat).

My car usually runs around 200F going down the hwy (summer temps - 95F). all of a sudden its running 215F. Stop/go traffic is usually 206-212F depending on how long i sit at the light. Now its 224Fin stop/go. I turned the heat to max on the hwy (to see if i had any air trapped in the system) and temp immediately plummeted to 195F - then slowly crept back up ( i guess that confirms that trick for an overheating car?) anyway - what gives?

The repair shop was apparently kind enough to put a used belly pan on for me - didn't tell me or charge me for it. I appreciate that kind of service. However...

Since this was the only change prior to last driving the car, I removed the pan and took a drive. Temps immediately back to normal. HWY speed temps dropped 10+ degrees back to normal (200ish) & Stop/Go dropped about 10 degrees to around 212-215 sitting at a light. Since I have never had a belly pan, I haven't seen one up close installed. It seals up the engine compartment pretty well - and I am sure there is a good (Autobahn) reason for it - BUT it traps a LOT of heat. If it raises the water temp that much, imagine how much warmer everything else is in there. The Efan ran twice as long to cool things down before switching off and would even turn back on sometimes to run for a few minutes more.

So no pan for me. I thought I would share my observations...HTH someone.
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  #2  
Old 07-26-2015, 09:05 AM
chrisn7 chrisn7 is offline
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You are assuming that your temp without the undertray is the correct temperature. The thermostat has 105 C stamped on it, which is a running temp of 221F, so you are choosing to deviate from the design temp, which is the optimum for economy. There should be a section of undertray around the gearbox as well as that under the engine

If you have a good look at the undertray parts, you will see that together they duct air around the exhaust system, which also keeps the footwell cool.
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  #3  
Old 07-26-2015, 09:21 AM
sealbeach740 sealbeach740 is offline
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chrisn7 - you bring up some very interesting points.
One of the advantages of the board is good open discussion of ideas for the benefit of all.

Besides the temp, most newer and higher performance cars are moving to a smooth undercar for gas mileage reasons.
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2000 740iS. MKIV, 16x9, DDEs controlled by Euro fog light switch, reversed steptronic +/- pattern, paddle shifters, clear corners, Basslink, iPod video with stereo audio, TV tuner, gauge rings, ///M pedals, backup camera with 'on demand' switch, quad brake lights, Dinan engine & tranny software, windows/sunroof close via remote.

2003 540iS. MKIV, 16x9, PDC, CWP, TV tuner, backup camera with 'on demand' switch, paddle shifters, windows/sunroof close via remote, iPod video & audio.
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  #4  
Old 07-26-2015, 09:38 AM
E38SkunkWerks E38SkunkWerks is offline
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Also helps with pesky water splashed trans...IMHO I don't think The Bavarians would put it there if it would hinder the car's reliability. Re-check your cooling system instead of ripping parts off...just my .02
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  #5  
Old 07-26-2015, 01:59 PM
TNe38S TNe38S is offline
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I am quite confident in the indicated water temps - monitoring the coolant temp thru the interval ii is what started my fan/tstat project (a 15 year old car with 150k+ miles does not need to run that hot IMHO). I have modified my Tstat housing to accept an 80C Tstat. BTW - this does not create a "check engine light" - but it does get logged it as an error when hooked up to a diagnostic machine.

I am sure they are logical reasons for why the engineers designed the belly pan and hot waters temps (emissions is my guess) - but they did that to certify and sell a new car. As an older used car, I am more interested in what cooler temps do for my repair bills. I have run the car this way for about 9 months - and I have not see any adverse effects - including fuel economy. The cooling system of these are are notorius...cooler can only be a positive.

I know everyone has their own ideas and this may not be for everyone. Thats ok, I am just passing this along.
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  #6  
Old 07-27-2015, 12:26 PM
chrisn7 chrisn7 is offline
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In the end BMW no doubt spent a lot of money researching the optimum operating conditions for their engines to achieve the right balance of emissions, mpg, engine wear and reliability, so its hard to understand why anyone would toss that out of the window based on nothing more than opinion. You are worried about repair bills, yet a sludged up engine tends to result from running too cool, usually at less than 100C. Water leak or sludge? I know which I would rather deal with....
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  #7  
Old 07-27-2015, 01:03 PM
E38SkunkWerks E38SkunkWerks is offline
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Quote:
Originally Posted by chrisn7 View Post
In the end BMW no doubt spent a lot of money researching the optimum operating conditions for their engines to achieve the right balance of emissions, mpg, engine wear and reliability, so its hard to understand why anyone would toss that out of the window based on nothing more than opinion. You are worried about repair bills, yet a sludged up engine tends to result from running too cool, usually at less than 100C. Water leak or sludge? I know which I would rather deal with....


+1, my thoughts exactly. Also your last point of air flow to cool the exhaust also makes me think of the possibility of directed airflow to the transmission as well...I personally like my transmission being nice and cool but I guess some people are different? LOL.
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  #8  
Old 07-27-2015, 02:35 PM
TNe38S TNe38S is offline
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I hardly think sludge is a concern LOL. By changing the thermostat, all have done is lowered the minimum temperature - i haven't set a max temp. the car gets plenty warm (222f today as its 100f here now). So it gets just as warm as it would with the an OEM tstat - the only difference is i am not forcing to stay there on a really hot day. I really don't see a downside.

But you are correct, it is all based on opinion. I am doing what i think is best for me (lower oils temps which the timing guides will certainly appreciate, and all that brittle plastic under the hood, and ABS modules that fail due excessive heat, and peeling valve covers, and plastic radiators, and expansion tanks, and.....).

Like I said...to each their own - just passing on what I noticed.
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  #9  
Old 07-27-2015, 06:11 PM
MR.WH1TE MR.WH1TE is offline
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TN so you live in the metro Nashville area ?
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  #10  
Old 07-27-2015, 06:55 PM
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Swank350 Swank350 is offline
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Lol, one thing thy didn't spend much time and research on is the good old timing chain glides)
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  #11  
Old 07-27-2015, 09:08 PM
E38SkunkWerks E38SkunkWerks is offline
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Originally Posted by Swank350 View Post
Lol, one thing thy didn't spend much time and research on is the good old timing chain glides)


Sshhhhhhh we don't speak of that....
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  #12  
Old 07-28-2015, 05:45 AM
chrisn7 chrisn7 is offline
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Quote:
Originally Posted by E38SkunkWerks View Post
+1, my thoughts exactly. Also your last point of air flow to cool the exhaust also makes me think of the possibility of directed airflow to the transmission as well...I personally like my transmission being nice and cool but I guess some people are different? LOL.
Yes, if you have a look at the X shaped second under tray section, this has a cut out in it for a swing down panel, like that under the sump. This panel however, has a triangular moulding in it transversely across the car (except 750 where panel doesn't clear the gearbox). The panel doesn't need the moulding to stiffen it, so I guess its there to direct air over the bottom of the gearbox....

Quite apart from temperature issues the underbody panels provide a first line of defence for various pipes, hoses, wiring, and brackets from road debris.
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  #13  
Old 07-28-2015, 07:00 PM
TNe38S TNe38S is offline
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Location: Collierville, TN
 
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Quote:
Originally Posted by MR.WH1TE View Post
TN so you live in the metro Nashville area ?
No - memphis area.
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  #14  
Old 07-30-2015, 09:22 AM
TNe38S TNe38S is offline
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hottest day of the year yesterday

looks good to me...
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