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      05-29-2023, 05:20 PM   #1
TheHaze
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N55 Coolant Flush Question

Hello all,

I'm planning on flushing my coolant soon as it hasn't been done yet and the car is 5 years old now. ISTA says to remove the hoses from the water pump to drain it, but I came across this video showing it getting drained from the auxiliary radiator in the bumper. I was wondering if this is a viable method on the M2 as it looks to be way less messy and easier to get to.

https://youtu.be/CVAUlvxrtOo?t=99
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      05-30-2023, 04:51 PM   #2
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Bump, and a related question. Should I go with the same blue coolant that was the factory fill, or swap to the new green stuff?
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      05-31-2023, 03:18 PM   #3
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From my understanding, you should drain from the aux radiator - its way easier and still gets the job done. For coolant, use the G48 blue coolant - it's available from BMW or most auto stores
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      05-31-2023, 04:42 PM   #4
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Quote:
Originally Posted by samsamdar View Post
From my understanding, you should drain from the aux radiator - its way easier and still gets the job done. For coolant, use the G48 blue coolant - it's available from BMW or most auto stores
Thanks! That's the method I was leaning towards too. I'll report back once I get around to doing this.
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      05-31-2023, 06:19 PM   #5
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Quote:
Originally Posted by TheHaze View Post
Thanks! That's the method I was leaning towards too. I'll report back once I get around to doing this.
Good luck and let us know how it goes! I need to flush mine too bc my dealer overfilled it lol
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      05-31-2023, 11:05 PM   #6
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Quote:
Originally Posted by samsamdar View Post
Good luck and let us know how it goes! I need to flush mine too bc my dealer overfilled it lol
You don't need to flush it if it's overfilled, just suck out the extra from the expansion tank.
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      06-01-2023, 03:20 AM   #7
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Changed my expansion tank a few days ago and I flushed the system by removing the hoses from the AUX cooler, I got a little over 5 liters out of the system. Seeing where the water pump sits I can't really see how that would get out more coolant since the water pump sits higher than the majority of the cooler and AUX cooler. AUX cooler is as far as I can see the lowest point of the system and very easy to access and no mess as a bonus. I think most of the coolant I didn't get out was left in the heater core in the cabin.
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      06-01-2023, 01:55 PM   #8
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Have to revise my last post. I ran the electrical water pump today to get rid of any air left in the system, you can do it by turning the ignition on -> turn the heat up to max on both sides -> fan speed to the lowest (not off though) -> hold the accelerator to the floor for about 10 seconds. Despite me vacuum filling the system I could fill up with another 0,6-0,7 L of coolant.
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      06-01-2023, 02:48 PM   #9
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Quote:
Originally Posted by Westersund View Post
Have to revise my last post. I ran the electrical water pump today to get rid of any air left in the system, you can do it by turning the ignition on -> turn the heat up to max on both sides -> fan speed to the lowest (not off though) -> hold the accelerator to the floor for about 10 seconds. Despite me vacuum filling the system I could fill up with another 0,6-0,7 L of coolant.
Thanks for the update. It's interesting to hear you only got 5-6L out of the car as ISTA states the capacity is 10.5L.
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      06-01-2023, 03:46 PM   #10
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Quote:
Originally Posted by TheHaze View Post
Thanks for the update. It's interesting to hear you only got 5-6L out of the car as ISTA states the capacity is 10.5L.
I don't think it's possible to get everything out as a lot is in the heater core as well.
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      06-02-2023, 09:55 PM   #11
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Thanks for this, y’all! I’d been rather dreading getting coolant all over me at the next flush. Going at it from the aux radiator sounds like a much better option, even if it doesn’t get everything.

And after several flushes, it seems likely that a majority of the original fluid would be replaced. Is that the right way to think about it?
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      06-08-2023, 10:30 AM   #12
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I finally got around to doing the coolant flush yesterday. After filling and doing the bleeding process 3-4 times, the car took just over a gallon of 50/50 mix. Overall, I would say the service was very easy. I didn't even need to pop the wheel off, just turned it all the way to the right to access the 8mm bolts in the fender liner. Only thing different than the video is our cars have 1 long under-panel at the front of the car that needs to be removed, rather than a small plastic piece on the driver's side like the video shows.
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      10-26-2023, 04:51 PM   #13
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TheHaze When you did the bleeding process (3-4times) did you use distilled water to refill the tank?
Im trying to do mine this week and its a first time for me
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      10-26-2023, 05:02 PM   #14
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Quote:
Originally Posted by BluOGM2 View Post
TheHaze When you did the bleeding process (3-4times) did you use distilled water to refill the tank?
Im trying to do mine this week and its a first time for me
You need to use a 50/50 coolant/water mix (or 60/40 if for some reason you live in an area where your car is exposed to < -300degC temps) mix to top off, if you only use distilled water you will dilute the coolant that's in the system even more.

Also, technically the coolant fill is supposed to be done with a vacuum filling device on M models (at least according to ISTA) to avoid air bubbles in the system, and you still need to run the automatic bleeding procedure after that.
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      10-27-2023, 03:59 AM   #15
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Quote:
Originally Posted by BluOGM2 View Post
TheHaze When you did the bleeding process (3-4times) did you use distilled water to refill the tank?
Im trying to do mine this week and its a first time for me
Nope, I used more 50/50 mix to top off between bleeds.
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      10-28-2023, 10:23 AM   #16
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I've done the coolant flush both ways on my M235, which physically is nearly identical to N55 M2.

It is WAY easier to do the flush from the Aux Cooler in the left/drivers wheel well. Easier to access. A simple un-snap 0-ring fitting. WAY easier to direct into a bucket to collect the waste. When you pull the hoses on the water pump it dribbles all over the front steering rack, even if you try to put form-a-funnels in place to direct flow.

And I actually got more fluid out of the Aux radiator (~5L )than I did when drained from the water pump (~4.2 L).

I need to do the pro-active coolant overflow hose replacement on my new-to-me M2, and I will definitely be doing the aux radiator drain procedure.
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      11-09-2023, 06:44 AM   #17
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Quote:
Originally Posted by ggggbmw View Post
I've done the coolant flush both ways on my M235, which physically is nearly identical to N55 M2.

It is WAY easier to do the flush from the Aux Cooler in the left/drivers wheel well. Easier to access. A simple un-snap 0-ring fitting. WAY easier to direct into a bucket to collect the waste. When you pull the hoses on the water pump it dribbles all over the front steering rack, even if you try to put form-a-funnels in place to direct flow.

And I actually got more fluid out of the Aux radiator (~5L )than I did when drained from the water pump (~4.2 L).

I need to do the pro-active coolant overflow hose replacement on my new-to-me M2, and I will definitely be doing the aux radiator drain procedure.
Very much appreciated for the valuable info. It's crazy how hard it is to find simple, straightforward info on the F87 when it comes to basic maintenance.
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      11-09-2023, 07:24 AM   #18
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Quote:
Originally Posted by c0riolis View Post
Also, technically the coolant fill is supposed to be done with a vacuum filling device on M models (at least according to ISTA) to avoid air bubbles in the system, and you still need to run the automatic bleeding procedure after that.
When I got my inlet and DV installed the local BMW mechanic I used said it'd be an easier job if we removed the water pump. He let it drain, then used the vac system to refill (once), and that's it, no multiple bleeds, and no automatic bleeding procedure. Car has been fine, even to The Dragon and back. I wonder what the auto bleed procedure does, and if it's something I should even bother with at this point?
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      11-09-2023, 07:44 AM   #19
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Quote:
Originally Posted by ///MPhatic View Post
When I got my inlet and DV installed the local BMW mechanic I used said it'd be an easier job if we removed the water pump. He let it drain, then used the vac system to refill (once), and that's it, no multiple bleeds, and no automatic bleeding procedure. Car has been fine, even to The Dragon and back. I wonder what the auto bleed procedure does, and if it's something I should even bother with at this point?
I mean, it couldn't hurt.
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      11-09-2023, 02:03 PM   #20
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Quote:
Originally Posted by ///MPhatic View Post
When I got my inlet and DV installed the local BMW mechanic I used said it'd be an easier job if we removed the water pump. He let it drain, then used the vac system to refill (once), and that's it, no multiple bleeds, and no automatic bleeding procedure. Car has been fine, even to The Dragon and back. I wonder what the auto bleed procedure does, and if it's something I should even bother with at this point?
You need to use it despite the vaccum bleed to ensure the heater core and the lines going to it hasn't trapped any air pockets. That's why it's specified to do so in ISTA regardless if you vaccum bleed it.
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