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Discussion Starter #1 (Edited)
Hello all! I purchased my 2000 BMW 323i about a month ago. It currently has 134k miles.

About five days ago I made a two hour drive to Tampa, FL and all seemed to be alright. I had the A/C on the entire time being that it was at least 90 degrees. When I was a few miles from my destination, I noticed there was steam coming from under the hood. I then noticed my temperature needle was steadily rising. I pulled over just as the car began to overheat, popped the hood, and noticed coolant was boiling over from the cap. After letting the car cool, I drove the remaining two miles to my destination and parked the car for the weekend.

When it came time to drive home, I turned the heat on full blast and did not have any problems with the temperature. Today I drove to work and turned the A/C on for about half a mile and when I reached the office it was beginning to get hot again. Any ideas what could be wrong with my coolant system? Thanks!
 

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2006 330ci zhp
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Check the operation of your electric fan and probably should do a complete cooling system refurb. That means waterpump, thermostat, expansion tank and probably hoses too.
 

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2016 340i xD 6-spd
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It could be as simple as the temp sensor on lower hose...could be fan...but it could be more than one thing too.

Read cooling threads...Mango has one up top. Learn about the system so you can diagnose what your issue is. If you were moving when you started overheating on your way to work, that could be therm. It handles most of the temp regulation in the system and reacts quickly if it has the right date. Check your pulleys and belts. If a pulley is hanging up, it could be slowing down the waterpump at slower speeds...you'd undoubtedly be hearing a squealing sound. The WPs are known to fail. Therms 'usually' fail in an open, and thus safer position, but they do sometimes fail closed.

Anyway, learn about the system and inspect things. A refresh is never a bad idea, but first figure out the problem best you can before you start tossing money at it.

D
 

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My ET blew up 2 month ago. Replaced it and everything seemed fine.
One day I was picking up a friend at the airport and traffic was a crawl. My temp needle started moving towards red so I had to shut it down. Last week I replaced water pump, t-stat, 4 pulleys, both belts, temp sensor, both hoses, flushed and filled with BMW coolant. Still the temp would shoot up when idling, and the a/c would intermittently work.

A few nights ago my radiator fan was running full blast hours after I shut down the car. I didn't know it at the time but I also had to replace my battery because of it. So in my case the fan was the culprit. Bought a new one and swapped it last night and my problems have been solved. A/C is cold all the time, no more overheating at idle, temp stays where it should (torque pro).

I'm at 111,900 miles on my 02 so it was time to do the cooling system refresh. I suggest you do the same. Do the full refresh outlined in Mango's stickied thread. Cost isn't bad at all, esp when compared to what the dealership or an indy would charge you.
 

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// Quandt AG (Retired) //
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My ET blew up 2 month ago.

One day I was picking up a friend at the airport and traffic was a crawl.
My temp needle started moving towards red so I had to shut it down.

Last week I replaced water pump, t-stat, 4 pulleys, both belts, temp sensor, both hoses, flushed and filled with BMW coolant. Still the temp would shoot up when idling, and the a/c would intermittently work.

A few nights ago my radiator fan was running full blast hours after I shut down the car.

I'm at 111,900 miles on my 02 so it was time to do the cooling system refresh. I suggest you do the same. Do the full refresh outlined in Mango's stickied thread. Cost isn't bad at all, esp when compared to what the dealership or an indy would charge you.
Everything you mentioned above are classic symptoms of the failing fan module on the electric fan shroud. Your fan motor was fine.

Do you recall the make of the bad fan assembly - was it original?

Readers of this post should take note that the fan module should be checked using the INPA test routine probably every 2 months in the summer and at least once in winter months. The fan module or entire assembly might have to become a PM Item as clearly replacing all of the cooling components cited in Mango's cooling refresh, although a preventative effort cannot save your car from the destructive effects of a single failing fan module.
 

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Everything you mentioned above are classic symptoms of the failing fan module on the electric fan shroud. Your fan motor was fine.

Do you recall the make of the bad fan assembly - was it original?

Readers of this post should take note that the fan module should be checked using the INPA test routine probably every 2 months in the summer and at least once in winter months. The fan module or entire assembly might have to become a PM Item as clearly replacing all of the cooling components cited in Mango's cooling refresh, although a preventative effort cannot save your car from the destructive effects of a single failing fan module.
Yup, it was definitely the final stage unit/relay on the fan. It was an original and I think it had a Bosch relay. I didn't have any more time or patience to mess around so I went ahead and bout a URO fan from Amazon. Got it the next day so I was happy about that. The relay on this URO fan is a lot fatter which had me concerned about fitment but it worked out fine. The housing of the relay is also made of plastic.

You should start selling these relay boxes since this is pretty common weak point. Include some connectors to make it easier on customers. You'll probably make some decent coin on it :craig:
 

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// Quandt AG (Retired) //
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I'm not trying to alarm you but closely monitor this new URO fan. It's very likely that it's the Chinese version of controller.I have 3 Chinese fan units that I've been dissecting and comparing to the two versions that Bosch made for the E46 and the one Siemens version. I have noticed the very latest "aftermarket" versions have moved to plastic boxes for the final output ic components (module). I have taken them apart and they are very poorly put together. Everything from the soldering joints to the PLCC chip inside is not to a similar standard when compared to Bosch. Even the motors - the Bosch uses copper brush guides - the Chinese are using tin. The Gen-1 Bosch modules are sealed in a clear silicone, the Gen-2 Bosch modules have a weatherproof seal completely encompassing the box lid. The Chinese have nothing - meaning moisture & salt will get inside. The main wire connectors are not clamped and soldered like the Bosch units they are merely soldered. Key connections on the Bosch use braided copper wire - the Chinese use single strand twisted. The logic chip in the Chinese is made in Taipei the Bosch uses a German made chip.

I here you about the cost of replacement. Our Bosch unit is not made anymore as an e46 assembly. I'm putting together a white paper (with help from a few other members) on just the electric fan as I think this item will cause the destruction of many an e46 in the next few years as the Bosch units fail and they are replaced with the cheaper units. If you have a working version of INPA it has a test routine for the electric fan and module. I recommend periodic testing - especially after the winter months when the module has been exposed to salt & snow.

I'm not interested in making money selling modules - I just want all of us to have better options than buying a ticking time-bomb (Chinese Fan Assembly) - One of these haunted my car for three years draining the battery and costing the unnecessary replacement of two FSR's, two batteries, rewiring the elephant trunk - twice; and countless hours trying to find a parasitic drain when it was a Jurassic drain by poor design.

i read many threads on here where folks replace entire cooling components ( like you did) only to see continual overheating and are advised they didn't bleed properly, when in fact the fan was never checked and may be the root cause.
 

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I'm not trying to alarm you but closely monitor this new URO fan. It's very likely that it's the Chinese version of controller.I have 3 Chinese fan units that I've been dissecting and comparing to the two versions that Bosch made for the E46 and the one Siemens version. I have noticed the very latest "aftermarket" versions have moved to plastic boxes for the final output ic components (module). I have taken them apart and they are very poorly put together. Everything from the soldering joints to the PLCC chip inside is not to a similar standard when compared to Bosch. Even the motors - the Bosch uses copper brush guides - the Chinese are using tin. The Gen-1 Bosch modules are sealed in a clear silicone, the Gen-2 Bosch modules have a weatherproof seal completely encompassing the box lid. The Chinese have nothing - meaning moisture & salt will get inside. The main wire connectors are not clamped and soldered like the Bosch units they are merely soldered. Key connections on the Bosch use braided copper wire - the Chinese use single strand twisted. The logic chip in the Chinese is made in Taipei the Bosch uses a German made chip.

I here you about the cost of replacement. Our Bosch unit is not made anymore as an e46 assembly. I'm putting together a white paper (with help from a few other members) on just the electric fan as I think this item will cause the destruction of many an e46 in the next few years as the Bosch units fail and they are replaced with the cheaper units. If you have a working version of INPA it has a test routine for the electric fan and module. I recommend periodic testing - especially after the winter months when the module has been exposed to salt & snow.

I'm not interested in making money selling modules - I just want all of us to have better options than buying a ticking time-bomb (Chinese Fan Assembly) - One of these haunted my car for three years draining the battery and costing the unnecessary replacement of two FSR's, two batteries, rewiring the elephant trunk - twice; and countless hours trying to find a parasitic drain when it was a Jurassic drain by poor design.

i read many threads on here where folks replace entire cooling components ( like you did) only to see continual overheating and are advised they didn't bleed properly, when in fact the fan was never checked and may be the root cause.
I hear you. When I saw the plastic module, it didn't leave me with much confidence :facepalm: I did email URO and they said it's warrantied for 2 years so I'll see what happens. I just needed the car fixed NOW so all in all, I'm ok with it. Now that I have the original fan out, I'm willing to mess around with other modules from other manufacturers just to have an extra fan on hand.
 

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// Quandt AG (Retired) //
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I hear you. When I saw the plastic module, it didn't leave me with much confidence :facepalm: I did email URO and they said it's warrantied for 2 years so I'll see what happens. I just needed the car fixed NOW so all in all, I'm ok with it. Now that I have the original fan out, I'm willing to mess around with other modules from other manufacturers just to have an extra fan on hand.
Great. Test the fan motor first directly at the two main contacts - BTW - you don't need to remove the motor cover to access, just remove the black plastic clip. If the motor tests ok and you are going to use it to build a spare then you may wish to remove the cover and inspect this conduit plate - it is notorious for corroding. Lube the shaft bearing/bushing and inspect the brushes. Coat the conduit plate with dielectric grease.

If you look at the last image - that's the quality of the inside of the Chinese fan motor.:cry:
 

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Wow, what a difference in quality :facepalm:
Thanks for the tips on the rebuild. I'll be doing this asap just to be sure to have that spare ready to go when this one goes.
 

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I was in your shoes little bit more than 2 years ago, I too purchased a URO fan from Amzn. Its been just fine thus far. Actually, it runs a test cycle every time I turn the car off. So a little bit of comfort there.
 

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I was in your shoes little bit more than 2 years ago, I too purchased a URO fan from Amzn. Its been just fine thus far. Actually, it runs a test cycle every time I turn the car off. So a little bit of comfort there.
Hey neighbor. Well that's good to hear. Thanks bud.
 

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// Quandt AG (Retired) //
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I had a Chinese Fan assembly in my 330 for 3 years - it worked great cooling the car at all the right times - only problem was every now and then it would drain the battery DEAD! Took 3 years to nail it down to the fan module.

Edit - In fairness I should note that I don't think this issue is restricted to the Chinese units - there was a chap on here last week had the same problem with a Gen-1 (Black box) Bosch
 

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I had a Chinese Fan assembly in my 330 for 3 years - it worked great cooling the car at all the right times - only problem was every now and then it would drain the battery DEAD! Took 3 years to nail it down to the fan module.

Edit - In fairness I should note that I don't think this issue is restricted to the Chinese units - there was a chap on here last week had the same problem with a Gen-1 (Black box) Bosch
LMAO, love the sig pic North. That's definitely you man! :thumbsup:
 

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// Quandt AG (Retired) //
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I was in your shoes little bit more than 2 years ago, I too purchased a URO fan from Amzn. Its been just fine thus far. Actually, it runs a test cycle every time I turn the car off. So a little bit of comfort there.
If it runs after you turn the car off it is not doing a test - it is either continuing to cool the car as the temp threshold is still exceeded. The test is only performed at startup per BMW technical docs although the fan may operate up to 10 mins after ignition is switched off to continue cooling:

Activation of the electric fan:
When the vehicle is first started the fan is activated briefly (20% of maximum speed), then it is switched off. This procedure is performed for diagnostic purposes.
The voltage generated by the fan when it slows down (it becomes a generator at this time) must meet the power output stages programmed criteria. This will confirm the RPM of the fan, if this is not met the signal wire from the output stage is switched to ground and a fault is set in memory.



The fan running after you shut off the engine is explained in this section of the technical documentation:


Error & Operation:
If the DME indicates a fault check the fan for freedom of movement. (If the fan cannot spin it will report an error).
After the initial test has been performed, the fan is brought up to the specified operating speed. At 10% (sensing ratio) the fan runs at 1/3 speed. At a sensing ratio of between 90-95% the fan is running at maximum speed. Below 10% or above 95% the fan is stationary. The sensing ratio is suppressed by a hysteresis function, this prevents speed fluctuation. When the A/C is switched on, the electric fan is not immediately activated. After the engine is switched off, the fan may continue to operate at varying speeds (based on the DME calculated catalyst temperature). This will cool the radiator down from a heat surge (typically up to 10 minutes).
 

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Living the e46 Cooling system nightmare

I just went through a similar scenario in my 2002 325xi w/AT except my expansion tank blew first. I replaced the expansion tank but could not run the car for more then a couple miles before boiling coolant and temp gauge nearing red (which is what caused the tank to crack). I had read other threads about causes and all of them pointed to water pump and thermostat. I just replaced the thermostat this past winter since it was staying open so I wasn't expecting that to be the cause, but after taking off the water pump and thermostat I saw some small cracks on inside housing of the thermostat. The new thermostat was staying closed now. I took out the innards of the thermostat to force it to be open, reassembled and that was the smoking gun. I'll replace my thermostat before winter. The water pump was fine. Hopefully this helps you or someone else. Also if you are troubleshooting the cooling system I like the recommendation of someone else and that is to use water until you fix the cause, drain your system and then fill with 50/50 mix.
 

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E46 Overheating

Hey gang,
I have a 2000 323i automatic that is overheating. Listed are the things that I have replaced:
thermostat
lower radiator hose
lower temp sensor]
expansion tank/w lid
radiator
fan clutch

Bled per instructions on the forum and then after about 15mins at idle with slight reving the temp was rising to about the 3o clock line
 
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