Radiator fan running from enging start to stop.

BMW 135i Overheating Repair Symptoms Radiator Fan Assembly Replacement
When the radiator fans stop functioning properly, the engine temperature will rise as there will be insufficient airflow to cool the radiator. The spike in temperature will be t... Read More
Radiator Replacement
A failing radiator can cause the engine to run hot or overheat. Most radiators are made of metal and plastic. The plastic parts can become brittle and crack over time, causing a... Read More
Thermostat Replacement
A thermostat that is stuck open can cause the engine to run colder than normal and set the Check Engine Light. It may also cause poor fuel mileage and the heater to blow cool ai... Read More
Water Pump Replacement
Water pumps require replacement if they begin to leak coolant or become noisy. Leaking water pumps can result in damage to the drive and timing belts, as well as cause the engin... Read More
Radiator Fan Motor Replacement
If the fan motor does not work, there will not be enough air movement through the radiator to dissipate the heat in the coolant. The symptom usually associated with a faulty fan... Read More
Radiator Hose Replacement
A coolant leak may be noted from the hoses. Coolant hoses can be damaged by oil leaks, or age. This will lead to swelling or cracking, it is suggested to replace the hoses befor... Read More
Coolant Leak Diagnosis
When the cooling system is not working to its full potential, normally due to a leak, the engine will being to run increasingly warmer with time and vehicle use. This is because... Read More
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I would recommend first to check the coolant level. If the coolant level is too low it can cause the fan to run if it detects too low of a coolant level. Also, the low warning can be a result of a low level. Make sure to check the level with the engine cold, and not running.

Wait till the engine is cold, remove the radiator cap, start engine and look for coolant gushing out of radiator or a lot of bubbles, its possible you have a blown head gasket.

repl temp sensor. run 12v to motor, does it run? could be resistors, they're hidden all over the car, thanks to the ******* engineers that put this piece of **** together. or the fan blades could be blocked.

radiator clogged, did someone put stop-leak in it? Remove thermostat drill two 3/16" holes in it 180degress apart, install 12 degree cooler thermostat.

check to see if fan clutch is working properly.

no the fan in front of the radiator is actully in front of the a/c condensor and serves to pull are across it for the a/c system. no fan on the motor will over heat the engine

Sounds like a cooling fan are not turning on. Assuming you have an electric cooling fan. It could be something simple like a fuse or a relay which is stopping the fans from working, or it could be something as bad as the motor burning out on the fan.

First overheat sounds like thermostat or fan switch. No start sounds like blown head gasket.

Flush Your Radiator

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this could be cause by the thermastate or the fan could not be working i would replace the thermastate and check fan make sure it is running when the car heats up

1. start the engine and leave the radiator cap open.
2. put a cardboard cover or a rug in the front of you radiator.
3. let it runs 20 minutes or more, see if it is overheated and see the water or coolant in the radiator circulated or not. If not, as soon as you have already changed water pump. thermostate and check the hoses, no leak, I think your radiator was blocked.

Did you put stop leak before?