2003 E46 325i Overheating

hoehne · 06-02-2006, 09:31 AM

I have a 2003 E46 325i with 67,000 miles on it and it is intermittently overheating. This same problem has happened on a cool day (73 F) and warm day (90 F).

While driving with the air conditioning on, the coolant temperature begins to rise above normal. This especially happens when sitting in traffic or at a stop light, but once driving regulates. Turning the air conditioning off doesn't have a profound effect. Turning the heat on full blact at the highest temperature does bring the temperature down. After having dinner and driving home, the temperature was back to normal and air conditioning was not turned on.

I have visually looked at at few things. There are two fans on the car. An electric fan in front of the condenser and mechanically driven fan on the engine. When the car temperature is above normal and sitting at idle in a parking lot, the mechanical fan is spinning, but the E-fan is not moving and has not moved. I have checked the fan fuse number 37 in teh glove box fuse panel and it is ok and even replaced it with the spare 50 A fuse, but fan still does not operature.

At this point, I do not know if it is a faulty fan, fan relay, or thermostat.

It could also be a water pump, but since the coolant temperature decreases when the heater is turned on, I assume that I have enough coolant flow. I have not checked the coolant level as the car was too warm at the time to take the cap off.

Is there anything else I could check or replace before taking it to BMW for a costly out of warranty repair?

Many thanks.

Bear · 06-02-2006, 05:48 PM

Turn on the AC and see if the electric fan runs, if so, the relay is OK. There is a two wire electrical sensor on right top of radiator and that is the device that determines temperature to activate electric fan speed unless AC is activated (some have this device lower on radiator). Since the temperture is OK at speed, I would suspect the viscous fan clutch (that aluminum casting on front of the water pump mounted fan). This fan sort of free-wheels at cooler temp and then grabs hold to help reduce engine temperature. This is a ddevice that the owner can replace by themselves, just remember that the big fan nut (32 MM) unscrews clockwise (left hand thread) and you will need to find a way to hold the fan from rotating as you try to remove the nut (yes there is a tool for this) available from mist online suppliers.

hoehne · 06-04-2006, 11:55 AM

Thanks for the reply. I have taken the car to BMW and they say the Aux Fan is dead and needs to be replaced ($500). The thermostat is broken and needs to be replaced. The AC system needs to be evacuated, charged, and leak checked.

I can see how the fan failure possibly led to high coolant temperatures and damage to the thermostat, but not too sure how the AC system was ever affected. I hope to get an answer on that Monday.

Bear · 06-04-2006, 12:43 PM

If the aux fan is toast, then that is an issue. As to the thremostat, you can replace that yourself and bleed the system and save mega bucks. I would take the car to an independent AC specialist and get and evaluation, if the system has never been opened then a vacumn is not generally needed,. A shop should put a flourescent dye in the system and check the pressures, the dye will glow green under balck light if there is a leak. If you do not have any leaks and pressure is low, get one can of 134a refrigerant and a hose to put the refrigernat in the car (low side, the fattest ofgthe refrig lines and you can purchase the 134a, except in Wisconsin, and a hose at any auto parts shop, in fact for a few bucks more they sell a hose with a pressure gauge) and add it and evaluate the system as to coooling from that point.

swordsman11868 · 07-19-2006, 01:30 AM

I have the same vehicle but have not had this problem.

To me it sounds like a bad thermostat.

Let us know the results!

thanks
-danny

BMWJosh · 07-19-2006, 04:49 PM

well we take a 32mm open end wrench and hit it (standing in front of the car)towards the driver fender,the impact works like a charm may take a few trys but works.The thermostat has two thin pieces of metal attached to it so its not uncommon for them to brake infact its sorta a common prob.As of the AC i don't get that one either.

Bear · 07-19-2006, 06:53 PM

BMW tech says aux fan is TOT, and I hope they are correct, but there is a fan temp switch )probably in upper right corner of radiator) that controls the aux fan and I would try replacing that ($35.00 maybe) before I went for a new aux fan. Could be a relay, but with car at idle and AC on, does the aux fan run? If yes, then the fan and relay are OK.

87esir · 07-19-2006, 11:24 PM

I wouldn't replace the fan switch just unplug the fan and put juice on it. If it works it will run and if it doesn't you need a new one.
If your water pump, thermostat, main fan are good and your radiator is clean your car should not run hot. (assuming your sleeves or head aren't cracked or blown head gasket ect...) Granted your aux. fan may be bad but I don't think it will solve your problem

Bear · 07-20-2006, 08:46 AM

I am not a 3 series expert, but I agree it may be more than the aux fan. In my 1988 750 when the fan clutch went, the aux fan could barely keep her cool (even at high speed on the fan) when driving in traffic. Granted the V-12 really fills the engine compartment and needs a lot of air flow to keep her cool.

Foz · 02-24-2007, 03:08 PM

I am writing with a similar problem in a 2001, 325ci E46. Everything you stated is exactly the same with my car apart from when the needle starts to move the main fan will spin for about 2 seconds and then stop. If I turn the temp to 32 degrees and full blast the temp will drop.

I have taken the car to BMW and they power flushed the system but that didn't seem to work, it only happens in traffic and cools as soon as the car moves. Like yourself I'm at a bit of a loss on what to do.

ladagosta · 08-22-2010, 11:11 AM

Foz,
do you still have your 325ci? if so can you assist with a wiring issue I would be so grateful to get mine back on the road instead of it becoming a lawn ornament.. thanks I have a post I need to ID where 2 wires connect.. simple as that and without access to one locally I am a sitting BMW.. thank you in advance if you would be so kind to pop your hood and find these 2 wires and let me know where they are supposed to go.. again thanks

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