[mweisdorfer]

I have been a lot of research on how to properly change the coolant on an N54. Here is what I have come up with.

1) Jack up the front of the car and use quality 3 ton jack stands at the lift points near the front of the car.

2) Remove the plastic under shield near the front of the car.

3) Make sure the engine is cold and open the reservoir fill cap.

4) Use a form a funnel and a large basin type fluid catch.

5) Open the blue drain screw on the drivers side and let it drain.

6) Remove the pipe near the AT and let it drain.

7) Remove the FMIC near radiator, which is two clips and two star screws, and let it drain.

8) Unscrew the black screw you now have access to after removing the FMIC and let it drain.

9) Put it all back together.

10) Mix a batch of quality coolant like an AMSOIL or BMW with 50% distilled water and 50% coolant; consider using a coolant booster.

11) Open the bleeder screw near coolant reservoir.

12) Begin to fill the system; it should take about 9 Qts. You should stop at about half way and turn the car on and run the heater full blast on the highest setting and fill the system the rest of the way.

13) Turn the car off with the key still in the ignition and lights on the dash visible and turn the heater on the lowest setting and press the accelerator all the way down for about 10-12 seconds until you hear the automatic pump kick on, which gets rid of all the air in the coolant system. It is advisable to have you battery on a charger for this process or perhaps fully charged prior to this process.

14) Open the reservoir and double check the coolant level.

15) done

Any advice? Changes to the list?

I am open ears

[robc1976]

Step 12 is wrong, full coolant until it comes out bleed screw....close bleed screw, fill coolant 1/8th" above normal fill.

[pHo_e92]

I find it easier just to remove the fmic first and then remove the blue screw to drain, but i think its different for AT and MT. I have MT so iirc you have to remove fmic to get access to the blue drain screw.

[jpirelli]

You can't do number 5 until you remove the FMIC.
Step 8: ???

[robc1976]

Originally Posted by jpirelli

You can't do number 5 until you remove the FMIC.
Step 8: ???

I never do it that way, I usually just take hose off heat exchanger.

[jpirelli]

Originally Posted by robc1976

I never do it that way, I usually just take hose off heat exchanger.

We 6MT guys have no choice but to drop the FMIC unfortunately

[R3N]

Is there any way to get all the coolant out through the heat exchanger hose? What about just flushing water through the expansion tank? I have some oil in my coolant system from the OFHG leaking and want to get rid of what's in there.

[robc1976]

Originally Posted by R3N

Is there any way to get all the coolant out through the heat exchanger hose? What about just flushing water through the expansion tank? I have some oil in my coolant system from the OFHG leaking and want to get rid of what's in there.

that us what I do when I do turbo installs...gets 99.9% out

[R3N]

Originally Posted by robc1976

that us what I do when I do turbo installs...gets 99.9% out

Could you elaborate a bit more on this please? Do you just flush through the expansion tank with water or the coolant mix? My concern is that if I flushed with water, there will still remain some water in the system and it will be difficult to get the 50:50 mix. Unless I am missing something.

[robc1976]

Originally Posted by R3N

Could you elaborate a bit more on this please? Do you just flush through the expansion tank with water or the coolant mix? My concern is that if I flushed with water, there will still remain some water in the system and it will be difficult to get the 50:50 mix. Unless I am missing something.

I do no flushing, I just disconnect at heat exchanger and it drains. After you unscrew expansion tank screw, fill with your mix slowly infill it comes out of screw (or 1/8" - 1/4" from lip). Once full tighten screw, connect car to battery charger (honestly not needed) put thermostat in car as high as it will go and fan on lowest setting and step on gas pedal (motor not running) and water pump will activate for 12 mins priming system.

[R3N]

I'd imagine to do a full flush you need to run the engine up to temp whilst adding water into the ecpansion tank to get all the old coolant in all the galleys, heater rad etc out