Temp. gauge a little past middle piont

[Bloody-Brit]

Originally Posted by cchino623

So i have a question M5James, If the Aux Fan in front is not working then could that be the reason my X5 begins to overheat in slow moving traffic as opposed to driving on the highway without traffic?

Yes,

The idea of the fans is to bring cooler air over the radiators, which effectively happens at speed on highways. When you are in city traffic, you do not have the same ram air effect, so air is sucked in using the fans.

[m5james]

Originally Posted by cchino623

So i have a question M5James, If the Aux Fan in front is not working then could that be the reason my X5 begins to overheat in slow moving traffic as opposed to driving on the highway without traffic?

Yeah, w/ this kind of weather lately, you'll need both fans.

1st - The mechanically driven fan that is mounted directly the engine. The fan clutch is filled w/ a wax like substance that gives in w/ resistance...hence why it sounds like an airplace taking off when you leave a stoplight, in the morning, etc. When they fail, its usually due to the wax leaking out or seizing. When it leaks out, the best test is something simple like taking a newspaper and seeing if that stops it (w/o breaking off blades of course) and/or if you can spin it freely when the motor isn't running. It should have some resistance.

When it seizes, it always sounds like an airplane...low rpm's, high rpm's. This is actually the worse of the two situations because people sometimes confuse it w/ the aux fan and continue driving the vehicle. I've seen at least two 740's where the owner continued driving the vehicle and the centrifugal force on the fan actually broke the plastic blades off, literally sending them through the hood. In the process it would break the radiator hoses, fan shroud and radiator itself...not pretty.

2nd - The aux fan a 3 stage electric fan that runs either from running the A/C and/or increased outside temps. I can't remember the code now, but the engine codes is basically saying that the 3 stage resistor isn't working.

Either way, w/ the temps here in Boise being around 110* lately, my buddies 750iL has been sounding like an airport w/ his fan going. You're aux fan is there to assist the mechanical fan w/ cooling just like the battery(besides starting) is there to assist the alternator when you're running extra electrical loads.

[cchino623]

So now 2 main questions M5James - 1) so did you mean to state that the mechanical fan is inside the engine? you didnt say where in or on the engine it was. 2) how do i know if my aux fan isnt working? If i turn on my A/C is it supposed to come on automatically? or will it take time? I was told by an indy mechanic that it seems my aux fan isnt working. but i wasnt sure if to take his word for it at the moment.

[anerbe]

aux fan helps with vehicle cooling, but it's larger purpose is for added condenser performance. it should be found if you are looking from the front of the vehicle (pusher fan). most time the mechanical/visco clutch engine fan (which is outside of the motor, in the front) is after the radiator. typically the setup with aux fan from outside of vehicle in is : pusher (aux) fan, condenser, radiator, shroud, puller (engine)

typically the aux fan will kick on soon after you turn on the ac, otherwise, the condenser is rendered almost useless in idle traffic.

no idle/slow traffic a/c performance is the typical indication that your aux fan isn't working. if the engine coolant temp also moves up on idle/slow traffic, your engine fan clutch may not be working properly.

to see if your aux fan is working or not, the aux fan should kick in when it's hot outside, and you are at idle stopped. it should sound like fans are powering up. the best way to check is with the engine cold, but the vehicle is heat soaked in hot weather. the engine fan should be mostly decoupled, but the pusher aux fan should be active.

[m5james]

Originally Posted by cchino623

So now 2 main questions M5James - 1) so did you mean to state that the mechanical fan is inside the engine? you didnt say where in or on the engine it was. 2) how do i know if my aux fan isnt working? If i turn on my A/C is it supposed to come on automatically? or will it take time? I was told by an indy mechanic that it seems my aux fan isnt working. but i wasnt sure if to take his word for it at the moment.

The mechanical fan is mounted on the front of the engine, between the radiator and all your accessories...alternator, waterpump, power steering, etc. I would assume you aux fan should come on when you turn on the A/C, but I can't be certain for sure...I think it's more engine and/or outdoor weather temp related. Do you know how to unlock your OBC and read the temp? Look on www.e38.org for unlocking OBC, or i'm sure you could find it here using search.

I don't know for certain w/ the I6's, but the V8's shouldn't ever go over 113*C, so by then the aux fan had better be on. I've never taken an X5 apart yet, but i'm sure that if you are mechanically linclined enough, you could connect the aux fan directly to a 12V source to make sure it works.

[m5james]

Originally Posted by anerbe

aux fan helps with vehicle cooling, but it's larger purpose is for added condenser performance. it should be found if you are looking from the front of the vehicle (pusher fan). most time the mechanical/visco clutch engine fan (which is outside of the motor, in the front) is after the radiator. typically the setup with aux fan from outside of vehicle in is : pusher (aux) fan, condenser, radiator, shroud, puller (engine)

typically the aux fan will kick on soon after you turn on the ac, otherwise, the condenser is rendered almost useless in idle traffic.

no idle/slow traffic a/c performance is the typical indication that your aux fan isn't working. if the engine coolant temp also moves up on idle/slow traffic, your engine fan clutch may not be working properly.

to see if your aux fan is working or not, the aux fan should kick in when it's hot outside, and you are at idle stopped. it should sound like fans are powering up. the best way to check is with the engine cold, but the vehicle is heat soaked in hot weather. the engine fan should be mostly decoupled, but the pusher aux fan should be active.

You've basically said the same thing, but if the car is overheating while sitting in traffic and/or stop and go driving conditions, it could be a combination of both. The mechanical fan is used the most in low RPM conditions, hence why it sounds like an airplane taking off. Old 90's 4Runner's were the worst w/ this noise. The aux fan is a back up for the mechanical not pulling enough air, and in combination w/ the A/C being on. We're on the same page.

[anerbe]

Originally Posted by m5james

You've basically said the same thing, but if the car is overheating while sitting in traffic and/or stop and go driving conditions, it could be a combination of both. The mechanical fan is used the most in low RPM conditions, hence why it sounds like an airplane taking off. Old 90's 4Runner's were the worst w/ this noise. The aux fan is a back up for the mechanical not pulling enough air, and in combination w/ the A/C being on. We're on the same page.

agreed, were on the same page.

ultimately, the mechanical fan/aux fan operating characteristics depends on the programming and the specs of fan clutch, which depends on the heat rejection requirements of the vehicle engine and HVAC. it is more expensive to have control logic on the aux fan for both engine and A/C performance vs. A/C alone. however, it could definitely be a combination of both if the vehicle needs it. I worked at Behr for 5 years - worst case scenario often determined if both are needed, and all the lesser conditions determined control logic between fan options.

still, the best test is to have car parked, heat soaked, turn on A/C max, and look through the front grill to see if aux fan runs and if the HVAC runs cold. if it doesn't run / no a/c performance, it's aux - then check to see if it's motor related or resistor/relay/ecm issue by plugging into 12v source. if it does run, check the mechanical fan.

[anerbe]

as an added note - electric fans (such as the aux) are most effective at idle, and drop in efficiency as the vehicle moves. you can see in the schematic of the aux fan ram air flaps, which means that the aux fan actually becomes a restriction when the vehicle travels at higher speeds, and air from moving actually will bypass the blade area.

mechanical fan is tied into the engine rpm, so the fan will get more powerful as engine rpm rises. it will start to slip when either the engine temp is lower, or if the engine rpm is too high. typically, the highest airflow from the engine fan will come at around 3k to 4k rpm.

if the engine fan is strong enough at idle to cool both the engine and the a/c condenser with HVAC on full blast, fresh mode, there's a very good chance the Aux fan isn't needed. since the X5 does have the aux pusher fan (and the assumption is that it needs it) the hot idle condition would most likely activate it.

[hunds02]

Sorry to revive this thread, but I have a few questions regarding the aux fan.

My aux fan has been inoperable for the past year. AC is cold in highway and useless in traffic. I know its my aux fan because it doesn't kick on when its really hot outside.

Before I get a new one and finally replace it, is there anyway I can test if its a relay issue, or just a faulty motor? And is it possible to buy a motor for it rather than the whole aux fan shroud assembly?

Thanks in advance

[m5james]

I haven't touched on some of these threads in years, so I might not know what I'm talking about...but with that said. I'd think you can do it via a process of elimination. Swap relays around with another of the exact same size, style, color, etc and see if anything changes. As for the fan itself, it's just a 12v motor that you can jumper directly to your battery, or I've even used 18v batteries from my power tools to test the fan I bought for my Harley F150 e-fan conversion.