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11-06-2010 12:51 PM #1
Auxiliary Cooling Fan issues BMW X5 2004 3.0
All, I had an expansion tank explosion one day and quickly replaced it only to realize that the root cause of the problem wasn't the expansion tank. Something was causing the motor to constantly increase its cooling temp. Low and behold after replacing the expansion tank and thermo I continue to see the temp rise while driving the vehicle under 15 MPH. In addition, the auxiliary fan does not turn on when I initiate the AC. I did witness it recently start up for a second or two then it turned off. So I'd like the begin my chase of the problem but I'd rather be efficient and economical with my time. A couple of things: I don't know where the relays are because I cant seem to locate a good site to explicitly define its locations. I know where the fuses are. I know where the fan switch is located on the lower hose (this might be the root of the problem), but I do not have a procedure to deduce this problem. Any kakua (assistance/help) would be hugely appreciated. Aloha, Ivan
11-06-2010 01:04 PM #2
04-27-2011 01:03 AM #3
05-03-2011 11:37 AM #4
Air Bubble in head? Fan Clutch?
One problem with BMWs is that when you change the coolant (which you are supposed to do every couple of years) it is VERY EASY to get an air bubble in the cylinder head, which, if left untreated, will overheat the engine, warp the head and basically kill the car.
This is less of a problem in the X5, which has a high hood height compared to the E36, for example. But many a shade tree mechanic has blown his own motor this way. Consult your Bentley manual (get one, if you don't have one, it is a treasure trove and costs less than one shop hour of labor) for more details.
I would also check your primary FAN clutch as well. This should engage at low speeds to cool the engine. The auxillary fan is really for the A/C system (although it will kick on if the car gets hot). At 15 mph there is little load on the car and the primary fan should keep it cool - if the fan clutch is working.
And yes, these are known to fail on occasion.
While the cooling system in the X5 is better than in older BMWs, the water pumps, electronic thermostats, radiators, and expansion tanks do get brittle with age and can crack, or even explode. This is usually due to aging plastic, not overheating, generally.
Many folks said that you should replace the entire cooling system at about 70K miles on an older BMW. This may be a bit extreme, and of course, the parts sellers are liking this.
But I think 100,000 miles or so is not a bad idea. Water pumps, in particular, can go bad, when the seal leaks and the bearings rust out - causing the fan to wobble and take out the radiator or other parts under the hood. In the Z3 forum, people have reported fan blades flying off and going through the hood.
I replaced my water pump, serpentine belt, tensioner, and thermostat at 100,000 miles. The radiator and expansion tank had been replaced at 50,000 miles (accident) so I left them alone. It is better to replace these parts in your garage, at a time and place of your choosing, then on the road in another State while in vacation. That's my philosophy, anyway.
I flush the fluid every couple of years and BLEED the snot out of it. Carry extra coolant with you (premix, 50/50 BMW coolant and DISTILLED water) in case it burps out more air while you are on the road.
BMW coolant is not THAT expensive, and if it prevents problems like this, why not use it? All the major catalog companies have it. I use it on all my BMWs.
Avoid other coolants, particularly GM Dexcool, which can turn to sand and clog everything. BTDT.
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