Radiator Fan Problem

M

mike87

Member
recently i've noticed that my fan (the one behind the radiator) comes on intermittently, even when it's not hot out and when the car has NOT been driven hard.

this fan will start up, get up to medium speed, then full blast for a few seconds before slowing down again, and then it will repeat this process continuously. i thought this was weird because i never realized it before.

fuses were checked and none were blown... what could be my problem???
 
Mike,

The radiator fan is controlled by a theromstat which detects the coolant temperature and as it rises above a pre set limit the fan will cut in to reduce the temperature. Sounds like either the thermostat is defective or the temperature sensor. Diagnostic check should identify the fault code.
 
now to my understanding, there is a thermostat and there is a coolant temp sensor on the lower radiator hose.

my gauge doesn't show that my car's overheating, the needle stops dead at 12 o'clock
 
Here's the temperature sensor..... http://www.realoem.com/bmw/showparts.do?model=BT32&mospid=47796&btnr=17_0249&hg=17&fg=05
and here's the termostat..... http://www.realoem.com/bmw/showparts.do?model=BT32&mospid=47796&btnr=17_0141&hg=17&fg=05
 
AlanJ said:
Here's the temperature sensor..... http://www.realoem.com/bmw/showparts.do?model=BT32&mospid=47796&btnr=17_0249&hg=17&fg=05
and here's the termostat..... http://www.realoem.com/bmw/showparts.do?model=BT32&mospid=47796&btnr=17_0141&hg=17&fg=05
Click to expand...

is the temp sensor the one that also feeds into the gauge on my dash? if so, i think that is working fine.. right?

would it be my thermostat be at fault? my car's not overheating and the heater blower/AC work fine. the thermostat you showed is the expansion tank thermostat (also, my car is an auto). is there another thermostat on my car? i looked up a few DIY and they all show the thermostat looking like something different that plugs into the engine block.

does the z4 have any relays controlling the fan i can possibly check? they weren't in the fusebox.
 
i tried it with AC off, same symptoms. when the AC is on, the fan is on continuously drawing air through the AC condenser/radiator.

now as far as i know, there is a coolant temp sensor on the lower radiator hose and another coolant temp sensor on the thermostat. i think my thermostat works perfectly fine... because i'm not getting any symptoms of the sticky or "stuck" thermostat. my car warms up in normal time and i'm not overheating.

i think my coolant temp sensors are okay too, because the coolant temp gauge on my dash is in normal operating order.. right?

there's 1cm of room between my AC condenser and my radiator and there's some leaves and crap stuck in-between there. i think i'm gonna clean it out and do a coolant flush (hasn't been done in a while). hopefully this solves the problem.

please let me know any additional thoughts! much appreciated
 
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