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Nuclear engineer
02/2012 X5 35d M57Y CPO 99K miles NOKIAN WR G3 12K miles
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Something to pay attention, trust and verify. Water coefficient of thermal expansion is quite small, IIRC 4%.
 

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I keep a maintenance logbook on an Excel spreadsheet. I note the date, mileage, and volume of coolant added. When the consumption (ml/mile) starts to go up, I start worrying. My 535i with 56k miles was using about 200ml every 10k miles. But, the last top off was 200ml after only 3.5k miles. So, I'm checking it more often and starting to think something bad might happen soon. The usual prime suspect is the expansion tank, followed by the water pump.
 

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Discussion Starter #4
I keep a maintenance logbook on an Excel spreadsheet. I note the date, mileage, and volume of coolant added. When the consumption (ml/mile) starts to go up, I start worrying. My 535i with 56k miles was using about 200ml every 10k miles. But, the last top off was 200ml after only 3.5k miles. So, I'm checking it more often and starting to think something bad might happen soon. The usual prime suspect is the expansion tank, followed by the water pump.


It took about a quart. Last checked 10,000 miles ago.


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It took about a quart. Last checked 10,000 miles ago.


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That's high. But, don't expect them to do anything about it until you see a puddle.

When the low coolant message came up on the X3, it took 700ml to get it back to MAX.

Don't fill the tank up all the way to the top. It's an expansion tank, and you want room for the coolant to... well... expand.
 

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Discussion Starter #6
That's high. But, don't expect them to do anything about it until you see a puddle.



When the low coolant message came up on the X3, it took 700ml to get it back to MAX.



Don't fill the tank up all the way to the top. It's an expansion tank, and you want room for the coolant to... well... expand.


Definitely no puddle in the garage. I don’t know that it was full 10,000 miles ago. Had the dealer service.


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Nuclear engineer
02/2012 X5 35d M57Y CPO 99K miles NOKIAN WR G3 12K miles
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It's an expansion tank, and you want room for the coolant to... well... expand.
Where does the gas air go when the coolant expands into the expansion tank?

Why doesn’t that hypothetical vent valve (and there is one) work for liquid as well as gas?
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 99K miles NOKIAN WR G3 12K miles
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.
 

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Porleau
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I've gotten a couple of warnings in my '17 340xi (8,500 miles) when it is very cold out (under 20 degrees). It's not due for routine service until June, so will just keep an eye on it.
 

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Got a message that the coolant level is low. Went away on restart. Level slightly low. Don’t see any evidence of leak. Anything to worry about?

Which motor do you have? 4 to 6 cylinder?
 

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Expansion tanks can develop several micro cracks that slowly seep fluid. In my experience no puddle or stain developed but the fluid slowly disappeared. Replaced the tank and problem disappeared.
 

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Got the same low coolant warning on my 2017 330i ...... less than 20,000 miles ......
which led me to discover that I have two coolant fill points / two cooling systems.

Brought them both up to spec ....... doesn’t seem to be recurring.
 

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I've gotten a couple of warnings in my '17 340xi (8,500 miles) when it is very cold out (under 20 degrees). It's not due for routine service until June, so will just keep an eye on it.
That last cold snap we had 2 weeks ago I got the low coolant msg several times, even once it said refill coolant. I took it into South Shore BMW and had them take care of it. They also refilled my washer fluid at the same time. I know adding coolant is easy enough you can do yourself but why not let them take care of it while under warranty. Create the paper trail so if something does develop later down the line, there's a history to it.
 

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Dave
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Where does the gas air go when the coolant expands into the expansion tank?

Why doesn’t that hypothetical vent valve (and there is one) work for liquid as well as gas?
The "gas air" doesn't go anywhere. It stays in the tank. And automotive coolant doesn't "expand."

Plus the vent valve will work for both liquid and gas. Reach the pressure limit on that relief valve and anything sitting there will come out. That's why they tell you don't open the cap on a hot engine with your ugly mug in the way.
 

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I've been getting the same message, its only happened recently during the days where temps have been significantly below average. I'm thinking that might have something to do with it?
 

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False Enthusiast
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I've been getting the same message, its only happened recently during the days where temps have been significantly below average. I'm thinking that might have something to do with it?


This is interesting. My 440 has 20,000 miles and has been trouble free. It normally lives in a garage at home and at work. It camped out overnight last week ( temps below zero) and in the morning when started, the add coolant light came on. Since there was no puddle or evidence of leakage, I drove to work and parked inside. At the end of the day, when started, the light did not come on and the warning was gone.
When I got home, after allowing the car to cool, I checked the coolant and added a small amount. I did not measure how much was added, but it was only a little.
Everything has been fine since. The car goes in for service soon so I will ask and pass on anything I learn.

jummo


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