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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 06-16-2011, 09:59 AM
whirlingbirdie whirlingbirdie is offline
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Mein Auto: 2001 540i
Car overheats when A/C is on AND CEL is on

Last Friday my 2001 540i (155K) overheated on the road. I pulled into a service station I sometimes use and they said my upper and lower radiator hoses needed to be replaced. I had them do it. I picked it up on Friday, drove about a mile with the a/c on, and the vehicle overheated again. Brought it back. They said it was the auxilliary fan and there was a recall on it. I was a service writer for 10 years (am laid off now) and know I've had it in the dealer, so I know it would have come up, but I called anyway and it was not under recall. Three days later the CEL came on, codes P0491 and 492, which is the secondary injection pump. I can drive the car with no a/c, defroster, etc. and it will not overheat.

My technical knowledge is limited and I can't do the work myself (not to mention I'm 8 months pregnant!) but I can understand it, just can't do it, if that makes sense. I can buy the parts and have a friend do it, but I want to make sure I am getting the correct parts. Funds are super limited due to me being laid off not to mention the $2000 I've dropped on the car since January.

Where would you start? I was told with those codes, I can drive the vehicle with no damage. I just can't turn on the a/c, which I can live without for now, but obviously need the defroster.

Thank you!

ETA: I am not taking it back to the place I had it at as they test drove the car without the a/c on. To me, a proper test drive would include having the ac on for an overheat problem on a 100 plus degree day.

Last edited by whirlingbirdie; 06-16-2011 at 10:00 AM.
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  #2  
Old 06-16-2011, 10:10 AM
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QSilver7 QSilver7 is online now
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Bleeding the cooling system is one of the most common issues on BMWs and this could very well be part of your problem.

There are hundreds of threads on properly bleeding the cooling system, take a look in the DIY section...or just google "BMW e39 bleeding cooling system" and you should get plenty of hits...some which may even include videos from YouTube.
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Q {BMW CCA Member #191509}
2006 E53 X5 4.4i (Sterling Gray) 12/05 mfg date <<~>> 97 740iL (Arctic Silver) 3/97 mfg date
(SOLD)
99 540iT (Orient Blue) <<~>> 95 525IT (Alpine White)
91 735iL (Schwarz Black) <<~>> 85 325e (Bronzit)

http://imageshack.com/scaled/grid240/822/e38e532ndsigpic.jpg

Last edited by QSilver7; 06-16-2011 at 10:13 AM.
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  #3  
Old 06-16-2011, 11:33 AM
Burning2nd Burning2nd is offline
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Mein Auto: E39 540, E36 328is, E83x3
When I get home ill right some details down , we have the same car and the same mileage wicked ...

Give u some ideas to look at , where are u located in nj?

Does the aux fan turn on when the ac is on? Doesn't matter that shouldn't cause a overheat
If it wasn't bled correct it would overheat regardless of ac on or not

I
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  #4  
Old 06-16-2011, 12:26 PM
rdc8118 rdc8118 is offline
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Can't say for sure on a 540 but on my 2003 530 the aux fan comes on when the ac is turned on.

Had the same problem last summer where my car would overheat as soon as i turned on the ac. It turned out to be a dead aux fan.
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  #5  
Old 06-16-2011, 12:29 PM
SeanPhang SeanPhang is offline
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at your mileage, a lazy clutch and the overall low efficiency of the old cooling system can cause your symptoms, i.e.: fine under low load, overheat when heat need to dissipate overwhelms the already low cooling capacity. the increase in heat generation can happen when a/c on or a hot day, probably both.

my car kept overheating (not that I let that happen, but I had to keep a close eye on it or it would happen) because the extremely low cooling efficiency of the old system (partially caused by my using stop-leak stuff in my leaking radiator). all the symptoms go away after cooling overhaul. now sits idle in 100 degree days without a problem.

so if no cooling overhaul is done, do it!
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  #6  
Old 06-16-2011, 12:36 PM
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QSilver7 QSilver7 is online now
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After re-reading my initial reply...I'd like to qualify my "suggestion". My suggestion to check that the system was bleed properly is based in that she had just had 2 hoses replaced...which means that there was ample opportunity for air to enter the system. Again, overheating & low coolant warnings right after working on BMW cooling systems are notoriously caused by an air bubble in the system...thus the suggestion to re-bleed or check to make sure the car was bleed properly. This would be easy to check and rule out as the culprit.

Second, the CEL and the overheating are probably coincidental more than causal...due to the fact that the CEL or SES light is a warning that there's an issue in either the evaporative or exhaustive emisions systems...and there's not many things in the emissions systems that would cause the car to overheat. Since the mechanics where working on changing radiator hoses that are near her secondary air pump...they could have unintentionally disconnected a vacuum hose which could be causing the PO491/492 codes. Again, something that can easily be checked...perhaps cracked hoses, or one or more that are disconnected or incorrectly connected.

Check the simple things first, then move on if you can disqualify them as the culprit.


Quote:
Originally Posted by rdc8118 View Post
Can't say for sure on a 540 but on my 2003 530 the aux fan comes on when the ac is turned on.

Had the same problem last summer where my car would overheat as soon as i turned on the ac. It turned out to be a dead aux fan.
She's got the M62TU engine which has a "variable" speed aux fan...it operates when it recieves a PWM signal from the ECU...unlike the older 2 speed aux fans which uses an inline relay....the newer aux fan has a slightly different set up and doesn't necessarily come on immediately when the AC (snowflake) button is pressed:

(E38 w/M62TU engine)
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Q {BMW CCA Member #191509}
2006 E53 X5 4.4i (Sterling Gray) 12/05 mfg date <<~>> 97 740iL (Arctic Silver) 3/97 mfg date
(SOLD)
99 540iT (Orient Blue) <<~>> 95 525IT (Alpine White)
91 735iL (Schwarz Black) <<~>> 85 325e (Bronzit)

http://imageshack.com/scaled/grid240/822/e38e532ndsigpic.jpg

Last edited by QSilver7; 06-17-2011 at 01:04 PM.
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  #7  
Old 06-16-2011, 01:48 PM
Burning2nd Burning2nd is offline
Under the lift arms
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Quote:
Originally Posted by rdc8118 View Post
Can't say for sure on a 540 but on my 2003 530 the aux fan comes on when the ac is turned on.

Had the same problem last summer where my car would overheat as soon as i turned on the ac. It turned out to be a dead aux fan.
this is correct all cars have aux fans that "should turn" on when the ac or defrost is activated
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  #8  
Old 06-17-2011, 01:00 PM
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I knew I had more e39 specific info about the aux fan...I just found it...it's basically the same info as posted above but also mentions the M52TU/M54/M62TU. Take a glance at the NOTE at the end of the article...the aux fan (for the aforementioned engines) may not necessarily turn immediately on when you press the AC button:



(e39 with M52TU/M54/M62TU engines)
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Q {BMW CCA Member #191509}
2006 E53 X5 4.4i (Sterling Gray) 12/05 mfg date <<~>> 97 740iL (Arctic Silver) 3/97 mfg date
(SOLD)
99 540iT (Orient Blue) <<~>> 95 525IT (Alpine White)
91 735iL (Schwarz Black) <<~>> 85 325e (Bronzit)

http://imageshack.com/scaled/grid240/822/e38e532ndsigpic.jpg

Last edited by QSilver7; 06-17-2011 at 01:06 PM.
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  #9  
Old 09-19-2012, 02:58 AM
beemer2003 beemer2003 is offline
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Good day everyone, QSilver7,
I have 525i E39 2003, lately its overheating with a/c on when stuck at traffic jam, in motion coms down and do not overheat despite a/c still on. even after adding almost 1/2 liter of coolent. any advise.

rgds
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  #10  
Old 09-20-2012, 07:02 PM
Burning2nd Burning2nd is offline
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Mein Auto: E39 540, E36 328is, E83x3
On all vehicles, Or ac systems in general , air must pass thur the condenser to cool the heated gas on the high side...

granted that it might not turn on right away... but with in a few seconds. the pressure switch will call for power to the fan.. the computer will see the engines temp and the fan will come to a low idle... In heavy traffic in high heat.. it will call for its 2nd speed... (high speed)

This is so simple....
steps of diag a over heating system

A: you have fluid
B: your fan is working? (in these cars it is a oil based fan clutch)
C :your water pump is good?

Aux fan will come on when the Defrost is on, oR the ac button is lit up..

With the ac button turned on... check for 12V Dc at the connector to the fan.... it is a four pin connector... check 12v to ground and look for continuity


and most of all... never ever ever ever ever use that radiator stop leak... that stuff is the devils work i sware to god... bad bad bad ****.. it does nothing but **** your engine up

if you have a cooling issue... dont drive it..

if you over heat in traffic but not when moving.. replace you fan clutch
if you loose Ac at a stop.. check your aux
If you over heat from cold to normal operation temp... check your water pump..


that covers everything related to this car... that is not a electrical relay or computer based issue.... thats for another day
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  #11  
Old 09-20-2012, 07:03 PM
Burning2nd Burning2nd is offline
Under the lift arms
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Quote:
Originally Posted by beemer2003 View Post
Good day everyone, QSilver7,
I have 525i E39 2003, lately its overheating with a/c on when stuck at traffic jam, in motion coms down and do not overheat despite a/c still on. even after adding almost 1/2 liter of coolent. any advise.

rgds
replace your clutch fan...

and dont get in traffic until you do so ... or you can start looking for a engine now
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  #12  
Old 09-22-2012, 03:14 AM
beemer2003 beemer2003 is offline
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Qsilver7, I could not open the link.. yet Burning2nd thank you, you gave a good simple explanation.... I will take my car to an electrician to check the second speed for the aux fan.. since clutch looks ok, and not losing AC, also when 2speed on fan goes tmp drops fast but it work only when reaches close to red. (do not you think)
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  #13  
Old 09-23-2012, 05:59 AM
pimposh pimposh is offline
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Common issue. Bad Fan.
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  #14  
Old 09-23-2012, 05:37 PM
Burning2nd Burning2nd is offline
Under the lift arms
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you can not tell if the clutch is good by looking at it... although when you compare a new one to a old one... you will be able to see the difference then

Good luck
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  #15  
Old 09-23-2012, 10:35 PM
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bluebee bluebee is offline
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Since this is an old thread resurrected, I'll simply reference this paragraph of cooling system debugging information for others to benefit:

- What to look for when your KTMP (1) or coolant temperature gauge indicates overheating (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) & what to look for in a perfectly normal E39 cooling system (1) & a picture of every failed part in the cooling system (1) & various techniques to properly bleed (1) (2) (3) & refill (1) & drain (1) (2) & flush (1) & what coolant to use (1) & what parts to replace (1) (2) & how to retrofit brass bleeder screws (1) (2) & what special tools to make or buy (1) & how to tell how old your cooling system is (1) (2) & how to test the cooling system auxiliary electrical fan (1) (2) (3) (4) & a DIY for replacing the auxilliary fan (1) (2) (3) & the infamous fuse 75 (1) & the aux fan relay (1) & how to diagnose lack of HVAC/IHKA heater core heat with cooling system (auxiliary pump) at idle (1) & a Behr radiator and Behr/Heat expansion tank autopsy (1) (2) & request for another Behr surge tank autopsy (1) & why new made-in-China Behr/Hella expansion tanks are DOA (1) & E39 Fan shroud removal DIY (Besian) (M54) & some of the better cooling system DIYs (cn90 1997-1998 M54TU) (cn90 V8) (aioros '99-03 M54) (Ågent99 '01 530i) (pelican 3-series) (bluebee M54B25) & tricks to replace the fan clutch nut (1) & lower-hose thermoswitch o-ring (1) & to non-destructively remove the heater hoses (1) or radiator nipple (1) or expansion tank nipple (1) (2) or Oetiker clamp (1) or misplaced thermostat wiring loom (1) or broken bleeder screw (1) & modifying the cooling system pressure cap (1), or using propanol-based zero-pressure fluids like NPG+ (1) (2) (3) (4) (5) or all-aluminum cooling system parts by Zionsville (1) (2) (3) aluminum radiators & what happens if you drive one mile too far with an overheated BMW cooling system (1).
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Each repair should invariably add to our knowledge base by the process of inexorable incrementalism.
Your job, in return, is to read the suggested threads, where the best people will 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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  #16  
Old 10-02-2012, 10:47 PM
beemer2003 beemer2003 is offline
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Burning2nd, Bluebee and everyone,

Thank you, thank you, thank you many times... for concern and detailed replies, radiator was almost out of water, and could not open upper bleeding screws, so had to fill, run car for 10 minutes and wait for next day to fill again... so on.. now it is ok, but the warning light at dashboard did not indicate any radiator water shortage.... any advise how to check this sensor.
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  #17  
Old 10-03-2012, 12:04 AM
Burning2nd Burning2nd is offline
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float switch in the tank is probably all gummed up

tank is probably on its last leg as well
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  #18  
Old 10-03-2012, 12:58 AM
beemer2003 beemer2003 is offline
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Any ideas, or where is the sensor/switch.
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  #19  
Old 10-06-2012, 03:10 AM
Burning2nd Burning2nd is offline
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switch is on/in the tank... Its been a while since i was in there... but if im not mistaken its part of the tank itself
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Old 10-06-2012, 08:13 AM
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bluebee bluebee is offline
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Quote:
Originally Posted by beemer2003 View Post
Any ideas, or where is the sensor/switch.
Why not follow the advice in the first few posts and search because you'd find entire threads on the sensor that way plus scores of pictures.

We've ALREADY given you the links.
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Each repair should invariably add to our knowledge base by the process of inexorable incrementalism.
Your job, in return, is to read the suggested threads, where the best people will 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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  #21  
Old 10-07-2012, 10:17 PM
beemer2003 beemer2003 is offline
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Burning2nd, Pimposh thank you for comunicating with me... Bluebee. appreciate your advise, but kindly note that I am not stationed around internet connection 24/7, nor have time to site on p/c. I found the sensor, but I will check how to test the it.

tnx again
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