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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 03-25-2016, 05:39 PM   #1
TS_Bimmer1997
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Overheating issue???

Ok so I've had my 02' 325xi for a little over a year now and I've had endless issues with the cooling system, however I've NEVER had an overheating issue until this point.

Back in December I had to replace the expansion tank and thermostat and since then I've had issues with the coolant light staying on even after I topped the coolant to BMW's procedure. Now whenever the car is in traffic for extended periods of time it will try to overheat until I start moving then the needle rapidly drops back to the center?

The only parts of the cooling system that haven't been replaced are the water pump and all of the radiator hoses. These seem to have nothing to do with what is going on as I have no leaks nor do I hear noises coming from the water pump.

Any ideas?
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Old 03-25-2016, 06:14 PM   #2
KawiNinjaZX
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Is your electric fan working?
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Old 03-25-2016, 07:34 PM   #3
TS_Bimmer1997
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Quote:
Originally Posted by KawiNinjaZX View Post
Is your electric fan working?
I checked it the other day, I let my car sit in the driveway and idle to see and it only kicks on for like 10 seconds and it doesn't seem to be spinning very fast. It would kick on like once every minute but only for like 10 seconds
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Old 03-25-2016, 07:48 PM   #4
KawiNinjaZX
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Usually if a car gets hotter when not moving it means the fan isn't spinning enough to simulate airflow like if the car was moving. With the fan working, once you hit operating temperature the needle should never really move.
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Old 03-26-2016, 08:59 AM   #5
markusmarkus
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Try this: https://drive.google.com/file/d/0B59...VlE/view?pli=1
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Old 03-26-2016, 10:08 AM   #6
Chris C
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I'd bet serious money that it's the fan. The same thing was happening to my car before I replaced the fan. It would overheat in traffic but once traffic died down and I could go at a good moderate pace the car would be fine. It started happening after my expansion tank failed also. I think the resulting coolant from the ruptured expansion tank affected the electronics of the fan. Anyway my car has a manual transmission and I diagnosed it the same way you did. I started my car in the garage and the fan wouldn't spin very quickly and when I continued to let it idle the temp gauge would creep up. After I replaced the fan and performed the same test the fan would spin more rapidly. The fan wasn't difficult to replace on my 2001 325ci. IIRC I replaced mine with a Bosche unit which had the same part number. The only thing missing was the BMW logo next to the imprinted part number and it was a lot less expensive. It's been working like a champ since. Good luck.
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Old 03-26-2016, 10:43 AM   #7
cvx5832
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Quote:
Originally Posted by Chris C View Post
I'd bet serious money that it's the fan. The same thing was happening to my car before I replaced the fan. It would overheat in traffic but once traffic died down and I could go at a good moderate pace the car would be fine. It started happening after my expansion tank failed also. I think the resulting coolant from the ruptured expansion tank affected the electronics of the fan. Anyway my car has a manual transmission and I diagnosed it the same way you did. I started my car in the garage and the fan wouldn't spin very quickly and when I continued to let it idle the temp gauge would creep up. After I replaced the fan and performed the same test the fan would spin more rapidly. The fan wasn't difficult to replace on my 2001 325ci. IIRC I replaced mine with a Bosche unit which had the same part number. The only thing missing was the BMW logo next to the imprinted part number and it was a lot less expensive. It's been working like a champ since. Good luck.

If I recall correctly the fan electronics are sealed, and on that year car was even encased in resin so I'm thinking it was the other way around. That is, a bad fan caused a lack of airflow, too much heat in the system, elevated pressures then eventually an ET rupture especially if it was old.

To the OP, I agree with the fan being the cause. Some here have reported a fan that responds to the "test" spin but no longer goes high speed. Any activation codes from the DME?

Lastly, if the coolant light doesn't go off, what brand ET did you install?
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Old 03-28-2016, 11:39 AM   #8
BMW-North
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All good answers above.

In the guide Markus pointed to above I included the INPA Electric Fan Test - I wanted to show you why I think it's the only reliable method to check the operation of the fan.

In the video below (made yesterday) I was giving my daughters 325xi an oil change before she headed back to school in NY. I ran a scan of DME and noticed a shadow error for Elufter 125 - it cleared no problem started car - fan spun like it should at start-up - checked DME - no new error - but I've seen enough of these fans by now (too much some would say) not to trust it. I set AC =ON and fan spun - but not very fast, and certainly not what I would expect owning several of these now for 15 years. So I hooked up INPA - sure enough I could not get the fan to respond to any DME fan speed request. I had to swap the donor fan in so she could head off to school this morning.

I suspect the cracked connection sealant and build-up of green corrosion on the PWM signal wire was causing intermittent operation and affected by ambient conditions of heat and moisture. I'll know more when I have time to inspect it thoroughly.





Edit: I will add - that in December I installed a new clutch fan in this automatic and it's my belief that the colder ambient temps (Winter) combined with the efficiency of the newer clutch fan prevented her from having an overheat condition till I was able to swap out the bad electric fan yesterday. One of the reasons I would rather drop two bumpers to replace the electric fan than to remove her clutch fan and drop in one of my spare e46 manual fans (fan delete). She's not an enthusiast! & I don't think she drives with one eye on the temp gauge like a lot of us do so she's better off having two fans in case this donor ends up failing before the end of semester.
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BMW-North E46 Electric Fan Guide

Bosch Fan Module: options using Volvo, Mazda & Ford

Making sense of INPA, EDIABAS, NCSExpert, NCS Dummies, DIS/GT1, EasyDIS, & Progman

Download a clean working copy of BMW Standard Tools that includes the special tests for E46 (3 Parts - RAR File format) Refer to the link above for the correct cable and install directions
BMW Standard tools Part 1
BMW Standard tools Part 2
BMW Standard tools Part 3

Last edited by BMW-North; 03-28-2016 at 06:36 PM.
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Old 04-04-2016, 05:52 AM   #9
TS_Bimmer1997
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Quote:
Originally Posted by cvx5832 View Post
If I recall correctly the fan electronics are sealed, and on that year car was even encased in resin so I'm thinking it was the other way around. That is, a bad fan caused a lack of airflow, too much heat in the system, elevated pressures then eventually an ET rupture especially if it was old.

To the OP, I agree with the fan being the cause. Some here have reported a fan that responds to the "test" spin but no longer goes high speed. Any activation codes from the DME?

Lastly, if the coolant light doesn't go off, what brand ET did you install?
The expansion tank is behr. I'm getting ready to order a new sensor to see if that fixes the issue
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Old 04-10-2016, 09:24 AM   #10
BMW-North
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Important PM item for Electric Fans

I believe the conditions that cause the majority of electric fans to fail can be avoided, and their life prolonged if owners do some minor PM work on existing or new replacement fans prior to install:

OK so a few posts up you will note that when my kid was home for Easter I did some PM or her car. During that I discovered that her Electric Fan was working intermittently. If you watched the video you will note that the INPA Electric Fan Test confirmed that her Electric Fan was not interpreting DME fan signals but the donor fan I pulled from my parts car worked ok.




I said I would inspect the failed fan - here's the results.

The terminals at the Bosch module had suffered from corrosion. Since this fan is installed in an automatic debris stuck between the motor cover and the radiator furthered the corrosion of the motor cover, however the Bosch fan motor is still fully functional only the module connections ( poor conductivity and high resistance) will not permit proper operation.




You will note that one of the 3 input connections at the Bosch module is kaput. It was hanging on by a thread and permitted intermittent fan operation.



However since the module terminals have corroded also beyond repair I will be swapping this Gen 1 module for a Gen 2 I have from a Ford Crown Vic and use the same motor and shroud to keep as a spare. (I will clean up the motor and re-grease the bushings)

The conductive strips on the fan motor board only have a slight amount of green corrosion and can be cleaned up, coated with dielectric grease which will prolong life.



Might not be a bad idea to periodically check, clean and coat any of these connections to ensure proper fan operation and longer life. THe Gen 2 Bosch modules tried to seal the connections in an RTV type material but they crack and allow moisture in. When I rebuild fan assembly's now I ensure that any of the 7 connections (fan, and module) all have RTV sealed connections and any other conductive areas are coated in dielectric grease.

Good luck.

For more info and photos of the different type Bosch fan modules and coating them for extending life:

BMW-North E46 Electric Fan Guide

Bosch Fan Module: options using Volvo, Mazda & Ford
__________________

BMW-North E46 Electric Fan Guide

Bosch Fan Module: options using Volvo, Mazda & Ford

Making sense of INPA, EDIABAS, NCSExpert, NCS Dummies, DIS/GT1, EasyDIS, & Progman

Download a clean working copy of BMW Standard Tools that includes the special tests for E46 (3 Parts - RAR File format) Refer to the link above for the correct cable and install directions
BMW Standard tools Part 1
BMW Standard tools Part 2
BMW Standard tools Part 3
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