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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 03-18-2014, 01:08 PM
thekage thekage is offline
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Mein Auto: 528i
Aux fan woes..

Long story short, car overheated on the freeway and had it towed to a friends shop. After checking the CEL he replaced the temp sensor and also checked out the AUX fan as it seemed to not be working. He jumped the conector from the temp sensor and the fan kicked on HIGH and proceeded to never turn off again - even when the key is out of the car. Checked all of the relays - they seem to be fine. And did a ton of research on here, most likely culprit seems to be that on this car, a 98 528i is probably a late model 98 and like 99s the aux fan is not controlled by relays but always has a hot signal. Perhaps when he jumped the temp sensor it blew the resister packs? Im looking at what to try next any thoughts?? Thanks in advance for the help!
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  #2  
Old 03-18-2014, 02:16 PM
edjack edjack is offline
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Take it back and make him fix it.
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  #3  
Old 03-19-2014, 07:42 AM
thekage thekage is offline
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He still has the car and is stumped.
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  #4  
Old 03-19-2014, 08:10 AM
JimLev JimLev is online now
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Where was the temp sensor located that he jumped? In the top side of the radiator or the lower hose?
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  #5  
Old 03-19-2014, 08:35 AM
thekage thekage is offline
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Quote:
Originally Posted by JimLev View Post
Where was the temp sensor located that he jumped? In the top side of the radiator or the lower hose?
The passenger side of the radiator.
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  #6  
Old 03-19-2014, 08:44 AM
cn90 cn90 is offline
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"car overheated on the freeway" = big problem because at highway speed, you don't need the aux fan at all.

There is something else going on.
When was the cooling overhaul done, if ever?
Mileage?

Do a compression tests and report back.
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  #7  
Old 03-19-2014, 09:44 AM
wenxin3262 wenxin3262 is offline
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Mein Auto: 1998 Alpine White 528i
Quote:
Originally Posted by cn90 View Post
"car overheated on the freeway" = big problem because at highway speed, you don't need the aux fan at all.

There is something else going on.
When was the cooling overhaul done, if ever?
Mileage?

Do a compression tests and report back.
agreed, last time I overheat on freeway was belt off, compeletly lost everything (water pump, power steering, alternator...)

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  #8  
Old 03-19-2014, 10:34 AM
thekage thekage is offline
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Location: usa
 
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Quote:
Originally Posted by cn90 View Post
"car overheated on the freeway" = big problem because at highway speed, you don't need the aux fan at all.

There is something else going on.
When was the cooling overhaul done, if ever?
Mileage?

Do a compression tests and report back.
Compression test was fine. After he installed new temp sensor car runs fine with no overheating.
Overhaul was done about 5k miles/6 months ago by myself. New water pump, new thermostat, new coolant housing, new belts, new hoses, new radiator, new coolant plugs, new mechanical fan and clutch, new radiator cap, coolant flush, filled with BMW coolant.
Mileage is 165,000
I dont think the fan was the problem originially, but NOW the fan is a problem. It wont shut off and it didnt start this until he jumped the sensor and it started doing this. Looking for ways to fix the fan not kicking off.

Last edited by thekage; 03-19-2014 at 10:36 AM.
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  #9  
Old 03-19-2014, 10:44 AM
cn90 cn90 is offline
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D/C the connector at the temp sensor (on the radiator).
Use an Ohmmeter and check the resistance with cold engine, if it reads "0 Ohm", the sensor shorted out.
I understand your mechanic just replaced the sensor but it is worth checking it.

A shorted sensor is the #1 cause of aux fan running non-stop!
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  #10  
Old 03-19-2014, 10:51 AM
thekage thekage is offline
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Quote:
Originally Posted by cn90 View Post
D/C the connector at the temp sensor (on the radiator).
Use an Ohmmeter and check the resistance with cold engine, if it reads "0 Ohm", the sensor shorted out.
I understand your mechanic just replaced the sensor but it is worth checking it.

A shorted sensor is the #1 cause of aux fan running non-stop!
Thank you sir. Will check out later and report back.
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  #11  
Old 04-01-2014, 07:59 AM
thekage thekage is offline
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Turned out to be the fan switch. Replaced it and the fan acted normaly. I also had a bad cap on the overflow tank. I think it was leaking under pressure. Replaced those two and no overheating, 45 miles later. Thanks cn90!!
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