Tap water for coolent top up...aahhhh!
 

I have been topping my x5 e53 4.4i 2005 coolent up with tap water and have just discovered recently thisis a no no due to the deposites. The first time I did it the bmw guy on the phone said to just use tap water. I can’t believe I didn’t investigate this earlier! Now I hope I haven’t stuffed something up with the deposites.

For the past 6 months I have been topping up with tap water. Lately, it has been 2L lots and now I have found the leak to fix. I know, extremely lazy on me not to address this earlier. So, I hope I haven’t damaged anything.

Waiting on delivery of coolent expansion tank to fix leak then I will get it flushed and new coolent. But what to do till then? I was thinking of buying some coolent (VALVOLINE Zerex G-48 RTU 20L) already mixed and top it up with that or even get some bmw coolent and mix. I am definately going to get some demineralised water. I just hope I haven’t stuffed the engine! Ahhhh....so frustrating that I did’t investigate first like I usually do.

I only hope I have a little of the original coolent in there and it hasn’t been expelled.

You'll be fine. Flush it out as best you can with distilled (demineralized) water. Then make sure you drain at least half the water out (I have to open the block drain on the 3.0L to get at least half out.) Then fill with pure BMW antifreeze until you've added half the listed capacity. Finish the fill/bleed process with your distilled water. You'll be good. The tap water isn't going to cause significant damage in the short run.

AM.

Just found out a saving grace....because I have been topping up so often most of the gunk could be expelled and not have had a chance to settle.

So, I have been topping up with demineralised water for some time now and finally all my parts have arrived to replace the aux water pump, the expansion tank and cap and later the heater control valve. Now, I am thinking about the bmw coolant. When I pull all the pipes off I will loose some coolant which I suspect is just water now. Looking into the expansion tank all I see is clear water. Is there any harm in just pouring coolent directly in after the pipes are all connected again rather than pre mix? I am thinking that most of the existing is pretty diluted and probably no bmw coolent left at all and pouring it directly in will eventually mix with the existing? I live in a climate where it never gets below zero degrees. I have read that it may cause uneven heat exchange on cooling the engine and could cause problems. I was then at a later stage going to do a full flush.

cheers

I already answered this above.

AM.

Get a coolant mix tester. Its like $2...

Thanks Big! I see you can get ones that use light refractometry. This will do the job after I add the bmw coolant Attack. cheers guys.

Have never used anything other than tap water in any of my cars and never had an issue. It's not like a domestic system where deposits from the thousands and thousands of litres that flow through over the years could leave deposits that cause issues. IMHO distilled or demineralised water is for batteries, not automotive cooling systems.

Remember, tap water isn't tap water. Hard, soft, clear, or dirty in appearance, it can have as many different chemicals added by a municipality as it has minerals added by time.

Around here, our water flows about 25' underground and is said to have fallen centuries ago and is filtered naturally. I dunno ab the content otherwise, but it does not leave mineral spots on a washed car. In some coastal regions, the sun will dry tap water into hard white spots on your car. In some other cities in the US, tap water is tested as unsafe to drink.

Extremely hard or soft tap water would be very bad for a cooling system.

I assumed that we were talking about "normal" tap water of the sort that most people in the western world are happy to drink. Not from Flint MI or holding all sorts of organic matter in suspension.



I live in an area of the UK that has hard water and it does indeed leave white spots if allowed to dry on a car. But to put it into perspective that sort of water has perhaps 500mg of dissolved minerals per litre. So by weight 0.05% minerals and the rest good old H20. Negligible, no?


But if using demineralised or distilled water floats your boat knock yourself out - it won't do any harm.