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Old 09-06-2009, 07:48 PM   #1
Daemonix
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328i Overheating, Radiator Fan not engaging

Hey all,

I recently had my car overheat on a sunny day a couple weeks ago, which caused it to blow the side out of the radiator resevoir and spill all my coolant. Further inspection of the vehicle showed that the electronic fan was not turning on, no matter what the temperature showed. I have a single fan behind the radiator, and don't have an aux fan for the ac... didn't come on my model.

I ordered a replacement fan shroud assembly (which includes the new fan motor, blades, and speed controller) and replaced it as well as the upper and lower radiator hoses. Also get the cheap lower radiator hose sensor while you're at it.

Fired the car back up, and it overheated yet again, without the fan moving one bit.

I tested the three wires coming into the speed controller; the brown, the red, and the small green one. The red has 12v going to it, and the others have nothing. (This is when the car is hot, off, and key to position 2.)

The coolant temperature in the radiator was super hot to the touch, which makes me believe that the thermostat is still working fine, allowing the super heated water out of the engine block and into the radiator.

I checked the lower radiator hose sensor (I did not replace this... for $16... no idea why...) and it didn't have any physical damage to it, but I tested the wires going into it. There are two wires, one that has about 5v and the other has nothing. I shorted these together with the engine on to perhaps simulate the closing of the circuit and hoping that the signal would activate the fan, but nothing happened, and still the fan doesn't move.

I also checked Fuse #37, and checked the ohms across it which read about .08 So that seems fine.

I'm not sure what else I can do at this point, other than replace the lower radiator hose sensor and really hope that it fixes it. If not... what are my other options? Thermostat?

Any comments or suggestions would be highly appreciated,

Thank you,

-D

Update:

Although I spent extra money probably replacing things that didn't need replacing, like the thermostat and upper/lower radiator hoses, regular maintenance is helpful in preventing breakdowns on the road.

Replacing the Fan Shroud Assembly, which includes the fan, fan shroud, and fan speed controller along with properly bleeding the cooling system most likely fixed this issue.

Do that first if you have the same symptoms/problem.
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Old 09-06-2009, 07:55 PM   #2
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Yeah, it might just be the sensor.
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Old 09-06-2009, 07:59 PM   #3
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My guess would be the sensor lower coolant hose sensor.
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Old 09-06-2009, 08:25 PM   #4
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Thank you for confirming my guess, I'll have one shipped to my house next week from AZ Autohaus. Once installed, I'll report back to this thread with an update. I know there have been other issues like mine, yet I have not found many solutions thus far.

-D
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Old 09-08-2009, 06:31 PM   #5
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Originally Posted by Daemonix View Post
Thank you for confirming my guess, I'll have one shipped to my house next week from AZ Autohaus. Once installed, I'll report back to this thread with an update. I know there have been other issues like mine, yet I have not found many solutions thus far.

-D
Thanks, An update would be much appreciated. I have the exact same problem and exact same car
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Old 09-19-2009, 03:11 PM   #6
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I ordered the sensor last week from AZautohaus for $24 and installed it about 30 minutes ago.

Checked my coolant levels and hooked up a OBD2 reader to the car so I could monitor temperatures in numerical value, instead of watching the temp gauge on the dash.

Watching the coolant temperature slowly crawl from 75 degrees on up to 247, I decided to shut the car down. (The in car gauge was at the 3/4 level, 1/4 away from the red zone.) The radiator fan still did not engage.

The top radiator hose is hot to the touch, and since I'm guessing that the temp sensor in the lower rad hose is the coolant temp that I pull the data from, the thermostat is still working.

I rechecked the 50 amp #37 fuse, which still looked fine, and even swapped it out with another 50 amp fuse. Still nothing.

Connected the old fan shroud assembly to the circuit plug with the key in the number 2 position and the car still very hot, and still nothing.


At this point, I'm throwing up my hands and probably going to have it towed to a local Euro shop to fix it.

$400 in, 6 hours later, a new fan, new fan shroud w/ speed controller, new upper and lower radiator hose, new lower radiator coolant sensor, new reservoir...

Any further suggestions?
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Old 09-19-2009, 04:23 PM   #7
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I just removed the thermostat, and although it doesn't have noticable physical damage, I'll be submerging it in boiling water to see if the mechanical function of the device still works.

I'll update afterwards...
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Old 09-19-2009, 04:37 PM   #8
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The water was boiling quickly and after submerging the thermostat, the piston did not move. Unless the temp required for the thermostat to move is higher than 212 degrees, this may indicate a failed thermostat.
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Old 09-19-2009, 04:39 PM   #9
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try finding the power wire to the fan. You should be able to follow that wire to some sort of relay or switch, which could be shot. Try shorting the power wire just to see if the fan runs. could be the fan motor.


I also have a 328i and mine overheated cracking my resevoir tank spilling all my fluid. It was the thermostat is my case

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Old 09-19-2009, 04:42 PM   #10
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I just replaced the fan with a brand new OEM version... at any rate... a new thermostat is in my future...
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Old 09-19-2009, 04:50 PM   #11
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mine is a 99 also but mine has a mechanical fan and an ac electric fan. Were there two different models in 99
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Old 09-19-2009, 04:51 PM   #12
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Damn, sorry to hear you've replaced all that stuff and still have problems. At that point I'd probably be like "FUUUU fan!" and just get a quality aftermarket fan like a Spal with its own replay and mounting brackets. $200 for that and it's a very robust and simple setup.

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mine is a 99 also but mine has a mechanical fan and an ac electric fan. Were there two different models in 99
Automatic and Steptronic cars have a mechanical and electric fan, while the manual transmission cars have only an electric fan.
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Old 09-19-2009, 05:04 PM   #13
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Damn, sorry to hear you've replaced all that stuff and still have problems. At that point I'd probably be like "FUUUU fan!"...
Oh yeah, I'm definitely there. I have a 86 camaro with an aftermarket fan/probe switch setup, but I didn't want to "Jimmy" this whole setup.

I'm trying to stick with OEM as much as possible... And on the bright side, I have a bunch of new cooling system parts installed for ~$400. At this point, I might just replace the water pump and not have to worry about cooling stuff for ~100k miles.

As usual, I will update this post when I install the thermostat next weekend. *le sigh*
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Old 09-26-2009, 02:33 PM   #14
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Oh yeah, I'm definitely there. I have a 86 camaro with an aftermarket fan/probe switch setup, but I didn't want to "Jimmy" this whole setup.

I'm trying to stick with OEM as much as possible... And on the bright side, I have a bunch of new cooling system parts installed for ~$400. At this point, I might just replace the water pump and not have to worry about cooling stuff for ~100k miles.

As usual, I will update this post when I install the thermostat next weekend. *le sigh*
ANy update?
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Old 09-27-2009, 02:49 AM   #15
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If you do find out what is causing the fan not to come on please update this thread as I am having the exact same problems! Already replaced fan and shroud as well as new expansion tank.

Thanks
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Old 09-27-2009, 03:23 AM   #16
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Definitely check the water pump. If the impeller is damaged, which may happen if you've got a pump with plastic impeller, it may not provide sufficient coolant circulation.
However, I'm not sure which year/model had the plastic design. The original water pump of my car had the metal impeller though.
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Old 09-27-2009, 06:45 PM   #17
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Fixed mine today by following the proper procedure for bleeding the system.
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Old 10-06-2009, 04:21 PM   #18
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Greetings all! Update here!

I fixed it!
Here's what happened:

I replaced the thermostat and filled the system back up with coolant/distilled water. Turned the car on and it still overheated.



Went back to the boards and read some more about how to "bleed" the cooling system. It turns out that if the heater isn't blowing hot air after you turn the car on, that there is air trapped in the system, and that I didn't bleed the cooling system properly.

I decided to go against taking the coolant plug out from the passengers side exhaust manifold area. That left one bleeder screw, 2 inches to the right of the main coolant fill hole in the top of the radiator reservoir.

I looked at the coolent level, which was full to the brim, and then loosened that screw. Within seconds, the level dropped down with a noticeable air purge coming out of the bleeder screw hole.

I then poured a good gallon or so of distilled water and coolant (50/50) into the resevoir until it filled it.

Turned on the car and squeezed the upper and radiator hoses and few times to push out air. I then replaced the bleeder screw and put the radiator cap on.

This time, the upper radiator hose got super hot which meant that the water was indeed travelling through the block and into that hose... unlike before. This is a good thing.

Within about 10 minutes of idle, my fan came on as noticeable heat was now coming off of the engine.

Took the car for a test drive and had no further issues with the cooling system. After letting it sit overnight from it's run, I refilled the resevoir another 1/4 gallon or so (from air moving out of the system) and capped it back up.

No further issues whatsoever.

Turns out the 10 step instructions for bleeding your cooling system is actually important. It's not like filling up an old truck radiator...
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Old 10-07-2009, 03:36 PM   #19
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How hard was it to change the radiator fan? Mine is doing the same but only when the a/c is on...
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Old 10-07-2009, 04:07 PM   #20
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Takes me 30 seconds now.

The fan behind the radiator? Nearest the engine?
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