Can I run the water pump on just distilled water?

I'm planning on flushing out the coolant on my BMW sometime next week.

I don't really want to take off the water pump hose and the other hoses to let coolant out. It'll create a big mess, which I don't really want.

So, I plan on unbolting the radiator drain plug and letting all the coolant drain out the radiator. Then Adding 2 gallons of distilled water and bleed the system/ turning the water pump on without starting the car.

After I'm done bleeding the system and draining the water out, I'll add the 50/50 BMW coolant.

Can I harm the water pump or other coolant items by just bleeding the system with distilled water?

If I turn the water pump on when there's no coolant in the system, can I harm the water pump that way by running it dry?

Any other things I should be cautious of?
The radiator isn't the lowest point so you're still going to have a lot of coolant remaining. If it were then BMW shop manuals wouldn't require removal of the hose at the electric water pump.

As for running the water pump with distilled water only. There's no issue with causing damage to the pump. Constantly running the water pump will use a lot of charge from your battery. The bleed procedure runs for 12 minutes.

Finally your coolant/water mix is going to be well below the 50/50 recommendation.

I guess it's possible that if you parked the car with the nose facing downhill you could get most of the coolant out. and then just refill with 50/50 mix but that's going to be a mess as well.

IMO I would just wait to change the coolant whenever you go in the replace the water pump or just pay a shop to do it.
 
Running just water in your system for a short period of time is fine. I just question doing this in Chicago in early March. Seriously wait for warmer weather unless that's somehow not an issue here...
It's supposed to be 61 next week :)
 
The radiator isn't the lowest point so you're still going to have a lot of coolant remaining. If it were then BMW shop manuals wouldn't require removal of the hose at the electric water pump.

As for running the water pump with distilled water only. There's no issue with causing damage to the pump. Constantly running the water pump will use a lot of charge from your battery. The bleed procedure runs for 12 minutes.

Finally your coolant/water mix is going to be well below the 50/50 recommendation.

I guess it's possible that if you parked the car with the nose facing downhill you could get most of the coolant out. and then just refill with 50/50 mix but that's going to be a mess as well.

IMO I would just wait to change the coolant whenever you go in the replace the water pump or just pay a shop to do it.
Yeah, that's what some people on the BMW forums said. They said to do a drain and refill with BMW 50/50 is the best route to go. Just repeat this procedure every 2-3 years.
 
The radiator isn't the lowest point so you're still going to have a lot of coolant remaining. If it were then BMW shop manuals wouldn't require removal of the hose at the electric water pump.

As for running the water pump with distilled water only. There's no issue with causing damage to the pump. Constantly running the water pump will use a lot of charge from your battery. The bleed procedure runs for 12 minutes.

Finally your coolant/water mix is going to be well below the 50/50 recommendation.

I guess it's possible that if you parked the car with the nose facing downhill you could get most of the coolant out. and then just refill with 50/50 mix but that's going to be a mess as well.

IMO I would just wait to change the coolant whenever you go in the replace the water pump or just pay a shop to do it.
This is what one forum member said:

Problem is: Anytime you add LESS-Concentrated mix of Antifreeze/Coolant than 50/50, you dilute the Concentration to LESS than 50% antifreeze. Bentley says capacity of cooling system is 2.23 Gallons with Automatic Transmission. So if you "don't want to make a mess" and forego draining at the pump (which is the LOW spot in the system), you MAY get ~ 1.5 gallons (6 quarts) of coolant out of system when you simply open the radiator drain plug.

Do NOT "UNBOLT" -- the plug is a PZ4/P4 fitting in a plastic housing with 19mm Hex to hold with 19mm spanner while loosening plug. FAILURE to hold that 19mm hex to prevent it turning WILL result in breaking assembly. Then you WILL have a "mess" on your hands ;-)

So HOW's your algebra? If you drain 1.5 of 2.23 gallons of 50/50 mix (do you even KNOW what it's concentration IS, or do we just ASSume? If you live in FL or TX (at least unless it's February ;-) the freezing point is NOT important, but the corrosion factor IS. If you fill the partially-drained system ONCE with distilled H2O, run the pump to circulate the new mix, and then Radiator Drain, refill with H2O, and repeat, after draining the last time, HOW MUCH water, and how much Antifreeze (by volume) remain in the block, trans cooler, etc.???

Point is, HOW exact do you want to be? What impurities, pH, or ion exchange issues are you seeking to address by the "flush" or Drain & Refill.
 
Yeah, that's what some people on the BMW forums said. They said to do a drain and refill with BMW 50/50 is the best route to go. Just repeat this procedure every 2-3 years.
IIRC the fluid is lifetime or 100k miles and it actually performs as advertised. It's why I always suggest to change the fluid when the water pump is changed out. You can of course do it as often as you want but it's not really necessary. I think lifetime coolant has been the industry norm for over a decade.

I've yet to see any evidence of coolant degrading and causing problems in a N-series engine.
 
If the cooling system is maintained in good condition, all it needs is a drain & fill done properly (remove hoses, plugs, knock sensors, etc. as needed). No flushing. If the cooling system is questionable and could benefit from a flush, it's OK to run straight water through the system briefly. But it should be restored to proper coolant chemistry as soon as possible.
I have called the local authorities many times over the years regarding proper disposal of automotive coolant. They have always told me to dump it into the toilet with a couple extra flushes to help dilution and treatment.
 
I wouldn't put coolant in the drain. I don't care what they say. It's much better to take it to a proper place than dump it.

Also losing 5-10% coolant isn't going to cause corrosion. Having old 50/50 is worse, in my book, than 40/60 that you replace every 3-5 years.
 
If you run your system with distilled water, then drain it fully, and fill it with 50/50, you will end up with much less than 50/50 protection.

There is water in the heater core and hoses, and other bends, that does not come out. If you flush, or do multiple drain/fills with water, you need to allow for up to a quart of water in your system BEFORE you start adding coolant. If you use 50/50, you end up with less freeze and corrosion protection. If you consider it comes out to 40/60 - a reasonable assumption -, that's still a 20% drop in additives and corrosion protection, and a 20F increase in the freeze protection (from -35 to -15F roughly) point. Not worth it at all. If you go the "full drain" route, you must refill with straight concentrate in a volume equal to 1/2 the total system capacity in order to get to 50% (or better yet, 60%). Then you top up it up in a second step with straight dH20.

If you don't really know exactly what's going on with a cooling system, play it safe and just drain the radiator. Refill that and then worry about it in a few more years.

It doesn't seem too hard to figure out how much water is still in the system, after say 3 rounds of drain and fills with water and now all you're getting is water out the 3rd time.

You know the total capacity of the vehicle. Let's say it's 12 qts. Let's say you filled it with water, ran it, and drained out 7 qts of water. That would logically leave 5 qts of water inside.

You would then add 5 qts of concentrate antifreeze, bringing the mix to 10 qts of 50/50.
Then you'd top off with 2 more qts of 50/50. That should get you darn close to a 12 qt, 50/50 mix.
 
I usually flush with water . Then add a gallon of 70% and top off with 50%. Usually gets me at -25F protection.

And used antifreeze is a great wood preservative. Also when mixed with Borax is a great termite and other wood eating insects treatment for wood.
 
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