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2018 REX - two coolant tanks

Posted: Tue Apr 06, 2021 8:21 am
by JonK
Hi All,

The manual is extremely vague on this issue. I have just checked the levels of the two small coolant tanks under the frunk RH side. One appears to be the coolant level for the REX engine and is fine. The other states it is for the A/C system and seems quite low.
What do I top this up with? The manual gives no information except ‘coolant’. I see i3/i8 coolant can be bought online but is that the stuff that goes into the A/C coolant tank? Thanks

Re: 2018 REX - two coolant tanks

Posted: Tue Apr 06, 2021 10:12 am
by MKH

Re: 2018 REX - two coolant tanks

Posted: Tue Apr 06, 2021 10:33 am
by JonK
Excellent thank you. Why on Earth the manual doesn’t state this I don’t know.

I’ll get some i3 coolant part no. 83512355296 - the blue stuff and top up with that.

Re: 2018 REX - two coolant tanks

Posted: Tue Apr 06, 2021 12:35 pm
by JonK
So it turns out that part number is correct for 60ah and 120ah vehicles but not 94ah card which is what I drive.
A call to BMW parts it will have to be!

Re: 2018 REX - two coolant tanks

Posted: Thu Apr 08, 2021 4:20 pm
by MagicCarpet
The 2 front coolant systems
The heater circuit coolant is not mixable with any other, only "i3 coolant" BMW part 83512355296, blue, silica free, previously green.
Electric machine = BMW G48, blue, nitrite & amine free, mixable or replaceable with: Castrol Radiocool NF or BMW 82192 211 913 or 194 or HT12
REX coolant in rear = same as E.M. as above.
The 3rd coolant is for the REX and located underfloor in the rear.

I'd be interested to know what the 83512355296 part has changed to for the 94AH models, or is it just that for 2014 that coolant was green but sometime it got changed to blue, with the same part no? Seems this coolant is special because high voltage parts are immersed in it like the PTC heater.

Re: 2018 REX - two coolant tanks

Posted: Fri Apr 09, 2021 3:05 am
by JonK
Many thanks for all this. The call to BMW parts confirmed that the i3 coolant 83512355296 is still correct for the climate coolant system tank in my car which is a 2018 94ah REX.
I have just topped up 50/50 coolant and water as the bottle advises so the levels are back to where they should be. It only needed 100ml or so.