2006 bmw 750li, radiator cooling fan not running when engine hot, I have replaced the sensor or switch, in the lower radiator hose with new, fan will not come on still. is there a fuse that might be preventing it from running, if so where is it?

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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
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Could be any or all three or a bad cooling fan. I'd start by replacing the thermostat since they are dirt cheap. After replacing the thermostat warm the vehicle up and feel the upper radiator hose if its hot the rhe thermostat opened and the water pump is circulating coolant next check the radiator it should be hot near the upper radiator hose and significantly cooler near the lower with an even heat distribution if any parts of the radiator dont get warm/hot then you radiator is plugged. Also you need to check the operation of the cooling fan with the engine warm turn on your ac that should immediately turn the electric fan on

a temp sensor only monitors what the engine temp is it will not cause the engine to overheat or run hot. check to make sure the rad cooling fan is working if not it could be a bad fan motor, temp sensor for the computer to turn on the fan or a fan relay. there are 2 temp sensors on motors. one is for the gage or light the other is to tell the computer to turn on the cooling fan.

have you checked the fuse and also the relay.

FAN RELAY

make sure the radiator cooling fans are coming on. GM has also had major problems with the lower intake gaskets leaking on the V-6 engines. sometimes when refilling the cooling systems air lock can occur. run the engine until it warms up and then turn off and let it cool down, if coolant level goes down repeat this process two or three times. other causes could be clogged radiator, or worse case scenario blown head gaskets. also i have on occasion got bad thermostats from the parts store. the upper radiator hose will get very hot when the thermostat opens. run the engine and hold the upper hose and when the t-stat opens the hose will get hot. then when the cooling fan comes on hot air will rush from from the fans. if the fans come on and the air is cool then there is a circulation problem. t-stat, clogged radiator, low coolant, head gaskets. good luck.

That is normal, it will not get hot without the thermostat. The water cools in the radiator and falls to the bottom and the bottom hose is cold. This is what cools the engine and stops it from overheating.

REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP.CHECK MECHANICAL COOLING FAN.SHOULD HAVE RESISTANCE WHEN TURN WITH HAND.IF FREEWHEELS FAN CLUTCH NEED TO BE REPLACED.CHECK TO MAKE SURE AUXILIARY ELECTRIC COOLING FAN RUNNING HOT WIRE COOLING FAN IF FAN RUNS.YOU HAVE FAULTY THERMO SWITCH LOCATED AT THE BOTTOM OF RADIATOR ON THE LEFT HAND SIDE ON 4 CYLINDER ENGINE FOR V6 ENGINE THERMO SWITCH LOCATED ON THE LOWER RADIATOR HOSE ON THE RIGHT HAND SIDE OF THE ENGINE COMPARTMENT. CHECK FOR BLOWN COOLANT FAN FUSE OR FAULTY RELAY.IF THE AUXILIARY ELECTRIC FAN DONT RUN WHEN HOT WIRED THE ELECTRIC FAN FAULTY.

1. Drain the engine coolant.
2. On Canadian models, disconnect the relay block that controls the day time running lights.
3. Detach the upper radiator hose.
4. Remove the lower radiator hose from the water outlet pipe.
5. On vehicles with an automatic transmission, remove the transmission oil cooler hoses from the cooler pipe.
6. Detach the cooling fan connectors.
7. Remove the Engine Coolant Temperature (ECT) switch connector.
8. To remove the radiator cooling fans, detach the 2 bolts and 2 upper supports.
9. Lift out the radiator and remove the radiator/cooling fans(s) assembly.
10. Remove the lower supports.
11. Remove the oil cooler hoses from the radiator.
12. Remove the lower radiator hoses from the radiator if they are still attached.
13. Remove the No.1 ECT switch.
14. Detach the cooling fans from the radiator.

Remember, SAFETY FIRST...never open, service, or drain radiator when hot. Serious burns or injury can occur. Always drain coolant into a sealable container. Cats and dogs are attracted to coolant and can be fatal to them if consumed. Coolant should be re-used unless it's contaminated or several years old.
Sure hope this helps you and good luck.

possible coolant blockage in engine. Fan does not run because temp sensor is located is part of coolant that is not getting hot. Describe loud noise please. You are likely facing terminal engine failure, however, try back-flushing coolant passages on engine. This may be tricky, but you could remove thermostat and try running engine, or fabricate a rubber stopper on the end of a garden hose to put in hole where thermostat goes, remove lower radiator hose and flush water as hard as possible. A big rust flake could be blocking coolant flow. PS: have you recently had any work done on cooling system? I have seen some stupids use so much sealant when replacing a water pump that excess blocks coolant flow. Lots of luck. "The rusty one"