[MissVito]

Advice please: hubby's 2021 M240ix -(his first BMW) bought it new: My husband just mentioned he's been getting a coolant warning message and poured some purified water into a reservoir. I mentioned that BMW requires special coolant and that his car has two separate cooling systems; I don't know if it's a good idea to just add water.

Now I'm reading that there's a specific process to coolant maintenance. (It's not like it's his old '06 Accord airport car) He mentioned the cap was very hard to take off. I wanted him to take it to the dealer and let them check it. (He has a lot of miles on it already) Could he have botched something up? Thanks for any advice

[overcoil]

I'm not a tech. I would say he had not 'botched' anything. That husband did the right thing by adding water. Purified, distilled, potable - thats a different subject I don't know enough about.

If the display message continues hit the dealer. In the meantime check under the hood for visible signs of leaking. Wet damp spots, white dried calcium looking spots.

[freakystyly]

Just make sure the engine is cold or at least hasn't be running in a couple hours. The system is pressurized like a pressure cooker, once the cap is cracked open the pressure equalizes and you can burn yourself.

Only topping off with distilled water is fine in warmer climates but the official stance is 50/50 coolant and water. All coolant really does is change the temperature the water boils/freezes at, and provide some lubrication for the moving parts like the pump.

[Ajowhan]

I think it partly depends on how cold the weather is in your area too. The coolant mix is usually 50/50 mix of anti freeze with distilled water. If its like a 1-2 times thing, its probably fine to just add distilled water since some people run even like a 30/70 distilled water mix in places that are not so cold and have zero fear of water freezing over..

You can only add so much before over diluting it. Another option is to add some 50/50 coolant mix, you can get some at probably any auto store.

[John in VA]

There are two reservoirs - one for the radiator/cooling system & one for the turbo. Maybe the one he didn't add water to is still low.

[Kernel Kurtz]

There is a specific procedure to draining and re-filling coolant. That does not apply to topping up. It is not unusual for these cars to require a small top up now and then, all of my BMWs have done this.

The bigger tank is the engine coolant tank, the smaller one is for the intercooler. The low coolant message is almost certainly for the larger one. Does not hurt to check them both, but I've not had to touch the intercooler level so far.

Given you are in Florida, topping up with distilled water (which is preferred over tap water) one time likely won't hurt your anti-freeze capability. I'd suggest when it requires topping up again that you use the approved coolant (BMW green for your MY) full strength to even it out, and then after that use the recommended 50/50 mix.

And yes, the cap is difficult to remove, this is normal. Be sure to tighten it till it clicks when you replace it. Of course if the low message comes back quickly (days or weeks rather than many months), you will want to get the system checked for leaks

Hope your husband is enjoying his new BMW!

[MissVito]

Originally Posted by Kernel Kurtz

There is a specific procedure to draining and re-filling coolant. That does not apply to topping up. It is not unusual for these cars to require a small top up now and then, all of my BMWs have done this.

The bigger tank is the engine coolant tank, the smaller one is for the intercooler. The low coolant message is almost certainly for the larger one. Does not hurt to check them both, but I've not had to touch the intercooler level so far.

Given you are in Florida, topping up with distilled water (which is preferred over tap water) one time likely won't hurt your anti-freeze capability. I'd suggest when it requires topping up again that you use the approved coolant (BMW green for your MY) full strength to even it out, and then after that use the recommended 50/50 mix.

And yes, the cap is difficult to remove, this is normal. Be sure to tighten it till it clicks when you replace it. Of course if the low message comes back quickly (days or weeks rather than many months), you will want to get the system checked for leaks

Hope your husband is enjoying his new BMW!

Thank you very much for that info. We should probably keep some BMW coolant on hand.

[jzeiler4]

Be aware that the 21 M240 uses the new GREEN coolant and not the old BLUE stuff. FWIW mine has also used a small amount of coolant in 17,000 miles.

[TrboMike]

You are adding so little water (or coolant) to the existing system you wont change the 50/50 mixture very much. 52/48 of water or coolant is insignificant. I wouldnt worry about.

He should have used distilled water, but again the amount he's adding is so little it will do almost nothing long term if he used tap water.

I would NOT go to a dealer "OH MY GOD YOU TOUCHED THE CAR WITHOUT PAYING US THOUSANDS OF DOLLARS we need to do a coolant flush and get some real super safe BMW made coolant in there just drop off your wallet bank account and trust fund account numbers with us AND WE'LL TAKE CARE OF YOU".

[Nickies]

Originally Posted by jzeiler4

Be aware that the 21 M240 uses the new GREEN coolant and not the old BLUE stuff. FWIW mine has also used a small amount of coolant in 17,000 miles.

The color of the coolant is not significant if it's BMW OEM and just for a top up of a few cups mix of 50/50.

[aerobod]

Originally Posted by Nickies

The color of the coolant is not significant if it's BMW OEM and just for a top up of a few cups mix of 50/50.

With run-out of BMW Fxx models, it shouldn’t be a problem mixing no matter what the original fill, but BMW introduced the green (or magenta) HT-12 coolant (not related to any other ‘traditional’ green coolant) in 2018, so it should be used in Gxx models. It is quite a bit more alkaline with higher silicates than the blue G48 coolant.

I would expect the Gxx models have only ever been tested from a gasket and corrosion perspective with HT-12, so G48 could cause issues.

BMW says that HT-12 can be used and mixed with G48 in cars originally designed for G48, but not the other way around.

G48 properties - https://www.glysantin.de/sites/defau...tt_g48_eng.pdf

HT-12 properties - https://sinpeks.elastyc.net/docs/dyn...0513_35715.pdf

[morphomeman]

This is a new car under warranty. Go to the dealer! That's what warranties are for.
Worst case, you don't go, something dreadful happens and they tell you that you voided the warranty with your DIY hack.

[Kernel Kurtz]

Originally Posted by morphomeman

This is a new car under warranty. Go to the dealer! That's what warranties are for.
Worst case, you don't go, something dreadful happens and they tell you that you voided the warranty with your DIY hack.

Some people live hours from their dealership. Long way to go to top up basic fluids, which has been a standard part of car ownership as long as there have been cars. Also I would not consider such topping up a "DIY hack". BMWs are fortunately not (yet) so user unserviceable that adding coolant, oil, or windshield washer fluid requires special tools and training.

[gosi]

You can check whether the big coolant cap has any dried up coolant residue on it or on the filler neck. From my experience the coolant cap or the heat module assembly are the main causes of coolant loss on this engine.

If you don't have a lot of coolant loss, I wouldn't bother checking the heat module, but the cap is very cheap and easy to replace yourself.