Is there a way to get the Aux fan to run early and after Run?

[M Audio]

Greetings,

03 530i is there a way to get the aux fan to run / come on early? Fan clutch seems to be working, and seems to go full on, at low speed and stop and go, which the car sees a lot.

I was hoping to have the aux fan come on early to help aid cooling in stopped traffic. I would like to run the aux fan 1-2Min post shut down to pull some heat out. I have the habbit ( when its hot out) to hold the engine at ~2k when parked and let up when I hear the mechanical disengage.

Hoping to help reduce heat soak and help engine life and bits..

99% certain I have the PWM fan, I had a older 528 with 2 speed mechanical and I could tap into the low speed and had it come on at ~195 via thermo-mechanical switch and after run was achieved via 2min electric timer

Than you,
//M Audio

[BimmerBreaker]

Running the fan more won't make the engine run cooler. The temperature of the coolant entering the engine is determined by the thermostat and the fans only serve to cool the coolant down in the radiator to a set temp. Cooling it down lower than the thermostat temp will just cause the thermostat to close.

I was hoping to have the aux fan come on early to help aid cooling in stopped traffic. I would like to run the aux fan 1-2Min post shut down to pull some heat out. I have the habbit ( when its hot out) to hold the engine at ~2k when parked and let up when I hear the mechanical disengage.

I doubt you are hearing the mechanical fan disengage, since it is "on" pretty much all the time. The clutch seamlessly disengages and engages there is no noise associated with it engaging. What you are likely hearing is the aux fan turning off, as that does make an audible noise.

The fact that the aux fan is turning off indicates the coolant coming out of the radiator is sufficiently cooled by the fan clutch alone at that point. So running the aux fan in addition to the fan clutch is completely pointless.

And running the fan after the engine is off serves zero purpose. You will be cooling the coolant in the radiator a little bit more, but once cooled past a certain point, the thermostat will just shut. And more importantly - with the engine off the water pump is off, so there is no coolant circulation in the first place. Merely blowing a fan at the front of the engine is insignificant as well, and you really don't want too much of a temperature gradient between cyl 1 and cyl 6.

I don't think there is a "problem" here at all except the mistaken belief that "operating temps = bad"!

How many M54's are having heat related issues with an otherwise intact cooling system?
What function does it serve to cool the coolant more when the inlet temp is determined by the thermostat?
What is the point of running the fan after shutoff when there is no coolant circulation?
If you can't answer those questions why do you think you can improve on a system designed by a team of very intelligent BMW engineers?

[M Audio]

"I doubt you are hearing the mechanical fan disengage, since it is "on" pretty much all the time. The clutch seamlessly disengages and engages there is no noise associated with it engaging. What you are likely hearing is the aux fan turning off, as that does make an audible noise."

Response: Untrue, I know the mechanical is always on, slipping via the clutch when unneeded. And the clutch locks / picks up accordingly with the temp it is exposed to. The Mech Fan with clutch engaged is a very different sound that the Aux fan. and I also can pop the hood, verify the aux is off, throttle up and feel the airflow, and 1-2min later you can see / hear / feel the mech fan / clutch disengage and the engine revs go up holding the same throttle position. You are correct and that I don't hear the clutch, its the CFM being pulled though the radiator.

I understand the fan does not cool the engine, it cools the radiator..

"running the fan after the engine is off serves zero purpose."

Response: Well why then do some cars (Mini, Porsche, Audi that I know of) Have a sticker that says "Warning E-Fan may turn on after car is shut off" Which I know Mini Does after shutdown some times as I had one, so its doing something...

The point of pulling the heat out of the radiator is that, it will be cooler, the T-Stat MAY open and exchange and cool the motor down quicker. and less thermal energy sitting under the hood cooking and shorting the life of all the rubber bits..

and being a engineer myself, I understand that everything is a compromise. and choices are not always made by engineers, but designers, cost is a factor and adding more bits to do something , whatever that something is, adds cost, complexity, design/test cycle time, increases time to market and much more..

my experience..

[StephenVA]

A few applications have an auxiliary electric pump that circulates the coolant after the engine is off. Most of these applications are turbo motors as the coolant needs to flow past the bearing case after engine off as most idiot owners pull off the hwy and turn off the key. This extra timed flow is to ensure life cycle of 60k. Everything else just gets hit with heat soak.

I think your question is
‘Can a coolant fan be programmed to run after key off within BMWs programming triggers” Not without cracking the program code to write it in.

if you have the temp s/w in the passenger side of the rad then you have the old style auxiliary fan (pusher fan), since that is the case it will only take a little bit of wiring a circuit to trigger the fan with a power off trigger timer. So you can get what you want.

NOW to the question of why you want to do this beside AS an engineering challenge escapes me as your vehicle has performed satisfactory for 20+ years without one.

As a fellow keeper of the E39 FLAME, it is always great to read that others are seeking ways to drive these great cars for years to come.
good luck with your project.

[M Audio]

HeyStephenVA,

My old E39 had the physical temp switch and I did this mod and I loved it and why, Because I could..

This E39 (03 530i) is PWM with the coolant sensor in the lower rad hose.

And yes, I am doing this because I believe it may help keep my loved E39 around a bit longer and I like a good engineering challenge..

Cheers,
//M Audio

[M Audio]

HeyStephenVA,

My old E39 had the physical temp switch and I did this mod and I loved it and why, Because I could..

This E39 (03 530i) is PWM with the coolant sensor in the lower rad hose.

And yes, I am doing this because I believe it may help keep my loved E39 around a bit longer and I like a good engineering challenge..

Cheers,
//M Audio

[crdiscoverer]

Depending on your coding skills, you can easily program an Arduino to do exactly what you want.

[JimLev]

All you need to do is supply the Aux fan a PWM signal and it will run. Power and ground are always at the fan connector.

I replaced my clutch fan with a 16” Flex-a-Lite unit and uses a PWM signal to run it.
In the summer when it’s 90-100ºF I keep the fan running for 5 min after I shut the engine off. It blows a lot of heat out from under the hood.
My reasoning is will extend the life of all the plastic under the hood. So far I haven’t had to replace any of it.
Pretty sure Philly does the same thing, probably to cool down the S/C.

[M Audio]

All you need to do is supply the Aux fan a PWM signal and it will run. Power and ground are always at the fan connector.

I replaced my clutch fan with a 16” Flex-a-Lite unit and uses a PWM signal to run it.
In the summer when it’s 90-100ºF I keep the fan running for 5 min after I shut the engine off. It blows a lot of heat out from under the hood.
My reasoning is will extend the life of all the plastic under the hood. So far I haven’t had to replace any of it.
Pretty sure Philly does the same thing, probably to cool down the S/C.

This! In bold above. The amount of heat that gets removed is huge.

I have a thermo-switch in my 70's Mopar with a SPAL fan, and it wired to run anytime the switch closes. (fused, and can controlled via a switch) and as such, when I shut the car off when hot, the fan will run for a few min, stop, and then start again for a bit and "tick-tock" a few times if its really hot.

Will look into Arduino / Raspberry pi, thank you Eric

[Iamthebull]

My mechanic wired up the Zionsville Radiator fan to run after the engine shuts off if it's at the 88C mark. Just runs for a minute or two.

[crdiscoverer]

Will look into Arduino / Raspberry pi, thank you Eric

Sure. You don't have to reinvent the wheel. Plenty of threads around accomplishing similar stuff:
https://forum.arduino.cc/t/automotiv...troller/549650
https://www.reddit.com/r/arduino/com...otive_aux_fan/
Etc...

[ross1]

This! In bold above. The amount of heat that gets removed is huge.

I have a thermo-switch in my 70's Mopar with a SPAL fan, and it wired to run anytime the switch closes. (fused, and can controlled via a switch) and as such, when I shut the car off when hot, the fan will run for a few min, stop, and then start again for a bit and "tick-tock" a few times if its really hot.

Will look into Arduino / Raspberry pi, thank you Eric

Combining this function with running the aux water pump would help regarding heat soak.

[blinky1041]

Having replaced many disintegrating plastic components (and also enjoying engineering challenges), I like this idea. Does the aux pump circulate coolant through the radiator or heater core?

I spent several years working at a plant that manufactured medium speed diesel engines (max 1000 rpm). These were turbocharged two-stroke v-engines, 710 ci/cylinder, in 8, 12, 16 or 20 cylinder configurations. Based on a N/A straight-eight designed in the 30’s that would power submarines in WW2, the V configuration engine started at 567 ci/cylinder, added ginormous roots blowers, was redesigned at 645 ci/cyl, replaced the blowers with a turbocharger (which was still gear-driven at low output levels), eventually landing at the 710 displacement with standard 16 cyl versions generating 4300 hp and high output versions rated at 4600 hp.

I mention this motor because most applications had a “soak-back” pump. This was an electrical auxiliary oil pump that was used to pre-lube the engine and turbo before starting, and was then run after shutdown to pull heat out of the motor and, primarily, the turbo.

The rebuild side of the business regularly got engines in with serial numbers dating back to late 70’s and turbos from the late 60’s. These units had been in constant locomotive service, with occasional rebuilds, for millions of miles. After-run heat rejection is a completely valid method to improve service life for IC engines.

I miss that place, it was really cool. The 16 cylinder engines were the size of a full-size conversion van and weighed 40,000 lbs. Keep in mind that the rated power of the engines was achieved at less than 1000 rpm. Feel free to calculate the torque generated.