Water pump running when in acc mode after coolant leak

[NickD]

I have a coolant leak in my '12 N55. It lost about 2-3 quarts of fluid so I topped it up with distilled water and fired it up to see if I could find the leak, which I did. However, now every time I turn the ignition on, the pump runs, almost like it's in bleeding mode. I haven't fixed the hose yet or drained the coolant, I'm hesitant on ordering parts as of yet until I figure out why the pump is constantly running. I didn't put it into the bleeding procedure. What would cause it to run as soon as I turn the ignition on?

[GoRomeo]

Originally Posted by NickD

I have a coolant leak in my '12 N55. It lost about 2-3 quarts of fluid so I topped it up with distilled water and fired it up to see if I could find the leak, which I did. However, now every time I turn the ignition on, the pump runs, almost like it's in bleeding mode. I haven't fixed the hose yet or drained the coolant, I'm hesitant on ordering parts as of yet until I figure out why the pump is constantly running. I didn't put it into the bleeding procedure. What would cause it to run as soon as I turn the ignition on?

Have run scanner yet? Any fault codes?

[Afam28]

Put it through the bleed procedure…
Top up as necessary…
Report back if it still running as described after…

[nevetstoj]

Originally Posted by NickD

I have a coolant leak in my '12 N55. It lost about 2-3 quarts of fluid so I topped it up with distilled water and fired it up to see if I could find the leak, which I did. However, now every time I turn the ignition on, the pump runs, almost like it's in bleeding mode. I haven't fixed the hose yet or drained the coolant, I'm hesitant on ordering parts as of yet until I figure out why the pump is constantly running. I didn't put it into the bleeding procedure. What would cause it to run as soon as I turn the ignition on?

Do you see coolant running in the reservoir? Might just be the fuel pump priming. Water pump is pretty quiet.

Having just gone through the water-pump failure experience, I know that usually happens when the DME thinks there’s a coolant system fault or air in the system. Since you lost a few quarts and refilled with water, the system probably detected a pressure drop or an air pocket and is triggering the pump to run as soon as you turn the ignition on. Basically, it’s trying to self-bleed or confirm coolant flow before the engine starts.

Once you fix the leak, top it up with proper coolant, and run a proper bleed cycle, it should go back to normal. If it still kicks on right away after that, it’s worth checking for a communication fault (LIN bus) or moisture in the pump connector.

Also, could be completely wrong, does the "Rest" button illuminate when you put the key in? Could be climate control issue telling the pump to run.