DIY Coolant change

[RoadRunner///M]

The below DIY is aimed at replacing the engine coolant on a BMW 1M N54 (with loosening FMIC to access the radiator drain plug).

Despite the ‘lifetime” coolant fill statement by BMW, these water pumps are prone to fail. Fresh coolant should certainly extend protection to components.

Tools:
• 8mm socket
• Flat head screw driver
• jack and stands etc

Supplies:
Quantity depends on the vehicle. The 1M has an aux radiator so has a coolant capacity of about 10L. Other N54’s are around 8L for a MT and close to 9L for an AT. When draining the cooling system, some small amount (5%) will likely remain. Coolant & distilled water is cheap, so just get a bit extra.

• 4.5L BMW coolant (3 x 1.5L bottles)
• 8L distilled water
• Optional - Redline Water Wetter (1 x 355ml bottle)
• Empty plastic mixing bottle with marked off lines for mix ratios.
• Catch pan with suitable capacity for old coolant.

The amount of coolant & distilled water depends on your climate conditions. I use the BMW coolant in 1.5L bottles which states a coolant to water ratio of 1:2 for conditions over -20 degrees Celsius. I actually ended up with about a 40:60 mix as better protection. So for my 2L mixing bottle I marked off, 60% water, 40% coolant.

Precautions:
• Only work on a COOL engine! Engine and coolant must be cool to avoid injury. Also adding cold fresh coolant to a warm engine is less than ideal for gaskets.
• Coolants can contain toxins, so be careful. Consider using gloves and safety glasses.


PROCEDURE:
Drain & fill:
• Jack up car (ideally the car should be level to drain coolant effectively)
• Remove the under-tray with the 8mm socket
• Remove the coolant filler cap
• Loosen the FMIC on each side from the hoses and the plastic attachments
• Loosen the radiator blue bleed screw. Once FMIC is loosened (not removed) you can get a screwdriver in the gap to the blue radiator drain plug.

• Once disconnected the water will drain out into the catch pan. Open reservoir to drain quickly (Because I only jacked the front and the car wasn’t level, I removed the catch pan after the coolant initially stopped draining and lowered the car to a level position to get a bit more coolant out. Then raised the car again)
• Tighten radiator screw after about 20 mins. Tighten up FMIC and check secure.
• Rinse off any spilled coolant with water.
• Add your coolant/water mix via the coolant filler reservoir. I also removed the bleed screw at this stage(don’t lose the rubber washer on the screw).
• Keep track of how much coolant you have added and confirm no leaks.
Bleed:
• Once the coolant reservoir appears full, the system needs to be bled of air. Leave the bleed screw open and filler cap off. Get into the car (leave door open) 1) turn the ignition system on; 2) turn climate control to max heat and lowest fan setting; 3) hold accelerator pedal down for about 10 seconds. Release the pedal when hear the water pump start to cycle. The water pump will bleed on and off for a few minutes. Wait until complete. The process will be aborted if you open close doors etc.


•
Check the coolant level in the reservoir is still full. I kept topping up during the bleed process.
• I repeated this bleed process a second time too. Keep topping up with fresh coolant mix.
• When the bleed it finished, tighten the bleed screw and replace filler cap.
• Rinse off area with tap water.
Check and finish:
• I started the car and let it idle for a 2 minutes. Check for warnings and leaks etc.
• Turn off the car. Replace under-tray etc.
• Take for a 10 minute test drive.
• Allow to cool and check coolant level.

[Harlequin]

Awesome DIY. Thanks mate. Will definitely make use of.

[hihnry]

Great DIY!

[Dackelone]

Very NICE! Thanks for putting this DIY together!!

[RoadRunner///M]

Originally Posted by Harlequin

Awesome DIY. Thanks mate. Will definitely make use of.

No worries. There was a fair bit of scale in the drained water. IMO this should be done every 2 years.

[froop]

Thanks for the DIY Ian! Really good write up.

I had my coolant flushed the other day at a mechanic but he didn't run through this bleed process so I did it yesterday at home myself. Just a few extra observations from my experience.

- Once the bleed process has started, whether you open and close doors etc didn't affect it for me. It keeps going until it either stops itself or the ignition is turned off.

- The bleed process took a lot longer than expected, closer to 10-15 minutes.

- It's didn't necessary to remove the bleed screw, but rather just loosen it a little bit. When it bleeds and overflows out of the bleed hole there is a little port which allows some of the coolant to squirt back into the coolant expansion tank. By not having the bleed screw removed or loosened too much, it could mean less coolant/water is wasted through overflow (maybe).

- I used probably 2-3 litres of coolant/water mix during the bleed process but this was mostly with the bleed screw removed or very loose. It was only towards the end that I experimented with having it only slightly loosened which still allowed the air to come out (could see and hear the bubbles) and the coolant to squirt back into the expansion tank.

[RoadRunner///M]

Originally Posted by froop

Thanks for the DIY Ian! Really good write up.

I had my coolant flushed the other day at a mechanic but he didn't run through this bleed process so I did it yesterday at home myself. Just a few extra observations from my experience.

- Once the bleed process has started, whether you open and close doors etc didn't affect it for me. It keeps going until it either stops itself or the ignition is turned off.

- The bleed process took a lot longer than expected, closer to 10-15 minutes.

- It's didn't necessary to remove the bleed screw, but rather just loosen it a little bit. When it bleeds and overflows out of the bleed hole there is a little port which allows some of the coolant to squirt back into the coolant expansion tank. By not having the bleed screw removed or loosened too much, it could mean less coolant/water is wasted through overflow (maybe).

- I used probably 2-3 litres of coolant/water mix during the bleed process but this was mostly with the bleed screw removed or very loose. It was only towards the end that I experimented with having it only slightly loosened which still allowed the air to come out (could see and hear the bubbles) and the coolant to squirt back into the expansion tank.

Agree, just need to loosen the bleeder screw a few turns. I actually just opened it at the start of the bleed process and then closed it and let the coolant cycle back into the open expansion tank.

I also give the coolant hoses a few squeezes during the bleed process. There wasn't much air in my car's system really and I probably wasted 4L of coolant mix, but suppose it is part of a flush.

[froop]

Originally Posted by Ian///M

Agree, just need to loosen the bleeder screw a few turns. I actually just opened it at the start of the bleed process and then closed it and let the coolant cycle back into the open expansion tank.

I also give the coolant hoses a few squeezes during the bleed process. There wasn't much air in my car's system really and I probably wasted 4L of coolant mix, but suppose it is part of a flush.

Maybe that's how you get out the extra capacity that you can't drain through the radiator drain hole.

[Flexo]

Is the Redline Water Wetter recommended? At what ratio should that be added? My climate is variable from 0 to 100 degrees F with a fair amount of the driving at 80-95 degrees in the summer.

[RoadRunner///M]

Originally Posted by Flexo

Is the Redline Water Wetter recommended? At what ratio should that be added? My climate is variable from 0 to 100 degrees F with a fair amount of the driving at 80-95 degrees in the summer.

To be honest I think Water Wetter is a waste in street cars with coolant mix. Just use 50/50 BMW coolant and distiller water.

[Ginger_Extract]

Thank you for this how to, cooling system flush is on my to-do list this summer.

[Hops128i]

Very nice DIY, i need to do this...

I've seen a coolant flush DIY (n52 i think), where they remove a hose to drain the block, is this neccessary?

[FIRSTM]

Thank you for this DIY, will tackle this project this week, great write up.

[4DrSpra]

So to drain you only need to open the screw on the radiator?

I thought there was another screw somewhere else that lets you drain the block also?

[4DrSpra]

Nevermind, already did it via that radiator screw only. I ran the bleeder screw open for half the water pump cycle then closed it and left only the cap open that way Instead of losing all that fluid it was put back in the reservoir.

I then drove it around the block for a bit and ran the water pump cycle again just for good measure.

This is what the old fluid looked like btw. don't have a record of when it was last flushed.

[Beasted]

Originally Posted by Basheezy

So to drain you only need to open the screw on the radiator?

I thought there was another screw somewhere else that lets you drain the block also?

So you don't drain the block? Just the rad? Surely that leaves a lot of unwanted grimey water still in there?

[4DrSpra]

Originally Posted by Beasted

So you don't drain the block? Just the rad? Surely that leaves a lot of unwanted grimey water still in there?

I would say this drains about 85-90% of the fluid. Ya not perfect, but not bad either. I wasn't sure where to drain the block from since my car is an auto and I've heard it's different from a manual.

If you really wanted to. You can do the process twice using just water the first time.

I also ended up removing my intercooler to make access a little easier and to clean up the ic also

[stunda]

Thanks for the DIY! Very detailed.

[JHZR2]

This is a great DIY, very helpful. On my 135i, however, I was not able to access the drain screw by simply disconnecting the FMIC. I had to remove the unit completely, as I couldn't get enough movement. Maybe it was something I did... Not sure... But since it was out, I could blow the fins out, and it's amazing how much dirt and dust has accumulated in just 15k miles!

[NorthernDancer]

Just did a change on N52
1. no intercooler so nothing in the way
2. maybe 13 8mm screws to remove belly pan
3. another 2 screws to remove small front belly pan
4. did not have a "big" screwdriver to remove plug; used 25 cent coin instead
5. my front end was maybe a big high so I only got 5 litres out; I let drain for about 15-20 minutes.
6. I slowly added 5 litres of fresh coolant/water mix. Engine took it all so 5L out and 5L in.
7. I bled by running engine for a while with CRT cap off and bleed screw open.
8. both belly pans went back on pretty easily

[bmw1racer]

Not sure how much current the electric water pump draws, but having a fully charged battery and/or have a battery charger attached during the water pump process might be a good thing...?

[bmw1racer]

Changed the coolant today (N52 engine) per the OP's procedure.

The bleed cycle ran for 15 minutes.

It took more time to remove/replace the belly pan than for the coolant change itself.

BTW, what's the shelf life (if any) of the coolant? I overestimated and bought two gallons of BMW coolant instead of just one.