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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 12-25-2013, 01:54 PM
tdsilk tdsilk is offline
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97 528i Overheating at idle

Hello,

I have a 1997 528i and noticed that the car is overheating when idling. I recently changed the thermostat and the temp was fine for about a week. Car is fine when moving, but at idle it goes near the "red". I tested the car today by checking the fluids to see if there were any leaks and what I noticed was no leaks. I also noticed that after about 20 mins at idle the tempo gauge rose to the "red" and the aux fan never came on. I also turned on the AC and still no Aux fan. Does this sound like a aux fan issue or sensor? Can someone help me determine what the problem is?

Thanks,
Troy
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  #2  
Old 12-25-2013, 02:02 PM
Mikes530 Mikes530 is offline
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Sounds very much like your aux fan. Easy DIY.
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  #3  
Old 12-25-2013, 04:22 PM
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dtadrian dtadrian is offline
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97 528i Overheating at idle

If you have a way to check for power to your aux fan, then do so and see if your getting power . If you getting power but fan does not come on, than its no good.


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  #4  
Old 12-25-2013, 04:54 PM
tdsilk tdsilk is offline
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I have a battery jump box and a multimeter. Will either of these work? If so, how?
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  #5  
Old 12-25-2013, 05:00 PM
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dtadrian dtadrian is offline
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97 528i Overheating at idle

Try reading thru this. http://www.bimmerfest.com/forums/sho...d.php?t=480135


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  #6  
Old 12-25-2013, 07:24 PM
Joker13 Joker13 is offline
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97 528i Overheating at idle

Did you bleed it properly first? I would start there first.


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  #7  
Old 12-25-2013, 11:00 PM
Mikes530 Mikes530 is offline
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Quote:
Originally Posted by Joker13 View Post
Did you bleed it properly first? I would start there first.
The symptoms seem to point to a fan-related issue:

- Overheating only occurs during idle (no ram air cooling)
- The aux fan "should" turn on when the A/C is activated
- The aux fan should kick in when overheating is detected regardless of the cause

To the OP - The design of the aux fan system was changed in 9/1998. After this date the final stage is integral to the fan itself and the whole system is controlled by the ECM. As your car is a '97 the fan is controlled by a switch mounted on the side of the rad.

There are checks you can do on post-1998 cars because they run through a diagnostic sequence at start up. I don't know if this diagnostic is run on pre-1998 cars. Maybe someone with a '97 or '98 could chip in.

On your car I would check for voltage into and out of the temp switch then apply power to the fan input. That should show you if the problem is in the switch, the fuse or the fan.

Last edited by Mikes530; 12-25-2013 at 11:03 PM.
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  #8  
Old 12-25-2013, 11:20 PM
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mjalloul11 mjalloul11 is offline
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Very little heat is given at idle, so rarly the AUX fan kicks in. But since it overheated and it didn't come on or with the AC on, it is busted. It could be anything from fuse to resistor pack to the fan motor itself. Also i would check the fan cluch on the main fan for the overheating problem.
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  #9  
Old 12-26-2013, 07:28 AM
tdsilk tdsilk is offline
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Thanks for all the info. I will check the fuse, switch then try to test the fan. I agree that it sounds like a aux fan issue. One other thing I noticed as the temp began to raise: the radiator/expansion tank seemed to try to push more coolant to the engine. This makes sense because of the lack of cool air generated by the aux fan. By the way, the fan clutch seems to working properly. If I do need a aux fan assembly any recommendations on where to purchase?
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  #10  
Old 12-26-2013, 07:35 AM
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  #11  
Old 12-26-2013, 08:09 AM
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Look to post #8-you have a fan issue. Both your mechanical and aux fans are not working. Search or go to the Wiki section for more info.
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  #12  
Old 12-26-2013, 10:24 AM
nhansen907 nhansen907 is offline
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97 528i Overheating at idle

This same problem happen to me a month ago. I changed radiator, and thermostat and still had overheating problem. I was told by a friend to park on a hill with the hood pointing up and open my radiator cap with car still running (Obviously do this when engine is cold) then wait a few minutes and top off with more coolant if needed. Hope this helps, bc it worked for my overheating problem!


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  #13  
Old 12-26-2013, 04:07 PM
tdsilk tdsilk is offline
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Thanks for all the help! I'm getting ready to try to hot wire the aux fan for testing. However, i'm not sure where the dual temp is located to test. Any ideas please?:-)
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  #14  
Old 12-26-2013, 04:22 PM
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Re: 97 528i Overheating at idle

Had the same problem after I had my coolant changed. Park on a hill and follow the bleeding process outlined on this site. Once all the air is out you should be good to go.

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  #15  
Old 12-26-2013, 04:44 PM
kmorgan_260 kmorgan_260 is offline
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Is your main cooling fan working? The aux fan should not be required to keep it cool if the other fan is working properly. Also, not sure it was mentioned but on my 97 the aux fan fuse is not in the standard fuse location. It is a big old 50 amp fuse by itself that you must remove the glove box to get it out.
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  #16  
Old 12-26-2013, 05:32 PM
skborders skborders is offline
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I agree with making sure it was bled properly and check the operation of the main (belt driven) cooling fan.
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  #17  
Old 12-27-2013, 09:40 AM
tdsilk tdsilk is offline
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The main cooling fan (the one in front of the engine) appears to be working fine. After installing the last thermostat (about a week ago) we followed instructions on bleeding the system.
We even tried bleeding the system again by tilting the car using jacking ramps in the front. We noticed that the coolant was lower and topped it off. We then moved the car off the ramp
and turned the AC on. After about 7-10 minutes the temp rose again near the "red". Turning the heat on caused it to lower. During this time the Aux fan never turned on. We will do some
more testing, but in the mean time we ordered a Aux fan assembly. If we find out we don't need it we will return it.
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  #18  
Old 12-27-2013, 03:53 PM
dvdlkd dvdlkd is offline
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Tdsilk, I also have a 97 528 and, years ago, had 3-4 incidents with the car overheating at idle. Each time this was fixed (at least temporally) by going through the bleeding procedure. About 4 years ago (90 thousand miles ago) i did the cooling system change out described in this forum by CN90. I also drilled a hole at the top of my new thermostat just as he describes and have not a single temperature indication past the normal midscale since. I am fairly certain that your temperature indication (for your gauge) comes off a sensor on the block/head while the temperature sensor for your aux fan comes off the cold side of your radiator (passenger side, feeding lower radiator hose). So the aux fan is supposed to come on if the radiator is not cooling enough. But the temp gauge sensor will detect the temp of the head where it is connected. The engine can overheat if not vented properly and the aux fan never get a signal to come on.
I suggest you at least go through the venting procedure again at a minimum. I really suggest you drill the top of your thermostat. While this has been debated on this forum as questionable as needed or not due to the vent built into the housing, the drilled hole in the thermostat gives you a vent at the top of the housing (where air would accumulate) while the designed vent is at approximately halfway down the housing. At any rate, this has worked for me for 4 years/90K.
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  #19  
Old 12-27-2013, 04:23 PM
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wat's dat noise
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tdsilk,
1.bleed and re-bleed.use both the bleed screws.
2. check that the viscous coupled fan works,you must feel air being pulled.just seeing the fan rotating does not mean it is clutched.
3.the aux fan is the last backup.generally this fan is not required during normal car operations and normally runs at low speed when a/c is switched on.

The fact that turning the heat on caused the temp to lower isolates the indication as suspect.
My bet is air in the system......bleed and re-bleed.
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  #20  
Old 12-30-2013, 11:06 AM
tdsilk tdsilk is offline
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Okay. Will try bleeding again. Thanks for all the help.
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  #21  
Old 12-30-2013, 09:13 PM
tdsilk tdsilk is offline
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Bled the system again and let idle with AC on for 20 minutes. So far so good. Needle stayed dead center. Will continue to monitor and keep everyone updated. As always thanks for the help!
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  #22  
Old 01-16-2014, 05:09 PM
tdsilk tdsilk is offline
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Looks like the temp spiked again! Lasted about two weeks this time. We noticed that there is some coolant lost which appears to be causing the temp spike after a couple weeks after the bleed.
The coolant appears to be leaking and settling in the splash guard under the car. We will try topping the lost coolant off to see what happens. Does this sound familiar?
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  #23  
Old 01-16-2014, 07:52 PM
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wat's dat noise
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there's your issue.insufficient coolant will of crs make your engine angry.fix the leak pronto.coolant sits on the splash guard and gets thrown out as you drive and probably leaks whilst you drive as well.
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  #24  
Old 01-17-2014, 06:09 AM
dvdlkd dvdlkd is offline
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You have to find the leak and fix it or this will keep happening. Is the leak causing your expansion tank to go dry or low?
From personnal experience with the same car, check the hose that comes off the head right behind your Oil filter housing (under the intake manifold) and runs over to the throttle body. There is a YouTube video of someone elses car leaking at this hose connection.

If this hose is leaking, it will leak coolant while the car is running and suck air into the head when the car is stopped and cools down. The coolant system goes to slight vacuum when the car cools down. Get enough air back into the head this way and you have to rebleed to get it out. There is also another hose off the back of head (near the firewall) going to your heater. With a mirror you can check this. But if this one is leaking, it would fall aft of your splash guard. Slow leaks are sometime hard to find but you find it if you are persistent and patient.
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  #25  
Old 01-17-2014, 01:19 PM
Burning2nd Burning2nd is online now
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first replace your fan clutch.. cause that whats stops you from over heating while at a stop.. (or less then 15mph)

Then figure out why your AUX fan does not work
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