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Discussion Starter · #1 · (Edited)
06 550i

A little over a month ago my 'low coolant level' warning came on. I promptly went to my indy shop they opened the reservoir and confirmed that my coolant level was indeed low. (first time this has ever happened).

They top off the coolant, did a pressure test to see if there were any leaks (found none), and sent me on my way.

Two days ago the 'low coolant level' warning comes on again. I check the coolant reservoir and it is again almost empty.

I have no liquid leakeage on my garage floor and have never noticed anything dripping from my engine. Today I take the car back in the shop and they cannot find a leak anywhere.

Where is my coolant going?
 

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06 550i

A little over a month ago my 'low coolant level' warning came on. I promptly went to my indy shop they opened the reservoir and confirmed that my coolant level was indeed low. (first time this has ever happened).

They top off the coolant, did a pressure test to see if there were any leaks (found none), and sent me on my way.

Two days ago the 'low coolant level' warning comes on again. I check the coolant reservoir and it is again almost empty.

I have no liquid leakeage on my garage floor and have never noticed anything dripping from my engine. Today I take the car back in the shop and they cannot find a leak anywhere.

Where is my coolant going?
i have a 545 and the dealer could not find a leak turns out it was a revisor that had a hair line crack. i actually had to take it off the car and then check
 

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06 550i

A little over a month ago my 'low coolant level' warning came on. I promptly went to my indy shop they opened the reservoir and confirmed that my coolant level was indeed low. (first time this has ever happened).

They top off the coolant, did a pressure test to see if there were any leaks (found none), and sent me on my way.

Two days ago the 'low coolant level' warning comes on again. I check the coolant reservoir and it is again almost empty.

I have no liquid leakeage on my garage floor and have never noticed anything dripping from my engine. Today I take the car back in the shop and they cannot find a leak anywhere.

Where is my coolant going?
How did the indy pressure test?
I was able to see the leak on my V8 coolant pipe (that runs through the V8 valley) with this pump to 10PSI, I drained the coolant in my case before hand, right away I hear hissing from the pipe, o-ring was pinched during water-pump installation, yeah it was my impatient making me work 3x as hard :mad:).

http://www.harborfreight.com/radiator-pressure-tester-kit-65053.html
 

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06 550i

A little over a month ago my 'low coolant level' warning came on. I promptly went to my indy shop they opened the reservoir and confirmed that my coolant level was indeed low. (first time this has ever happened).

They top off the coolant, did a pressure test to see if there were any leaks (found none), and sent me on my way.

Two days ago the 'low coolant level' warning comes on again. I check the coolant reservoir and it is again almost empty.

I have no liquid leakeage on my garage floor and have never noticed anything dripping from my engine. Today I take the car back in the shop and they cannot find a leak anywhere.

Where is my coolant going?
I have this exact same issue on my '07 530. Did the pressure test as well with no leaks found. Every couple of months I have to top off the reservoir. I'd love to get to the bottom of this one.
 

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At this time of year most coolant leaks happen when the engine is cooling down or when it is sarted after sitting all night and as the engine and other components warms up the leak seals itself due to the components expanding. When my customers lose coolant with no obvious signs of leakage I have them leave their cars overnight and pressurize the cooling system overnight so when everything does cool down and relax you can see where the leak is being that I have the cooling system pressurized.
 

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Mine was sort of doing the same thing, every 40-50 days my light would come on and I would be down 20-30 oz. of fluid. I finally took it after the third light and I had a hairline crack in my radiator. Never saw one drop of fluid under the car. I think it is because of all the under armor our cars have.
 

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Discussion Starter · #9 ·
It was the expansion tank, with a very tiny drip leak from the bottom that would burn off/collect elsewhere before making it to the actual ground. I have heard these typically go around 80k, I am not yet to 70k but sounds about right.
 

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'18 BMW X1, '14 ML350, '07 C280
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Cooling system is a 'closed-loop system'. So, if you are having to add coolant (regardless of frequency/amount) there is a leak - however small it is. Coolant should be mixed 50/50 with distilled water. If the water content is too high, I can imagine water may be evaporating... just a thought.

If my car needs coolant to be added, I would find out where it's leaking... It's not that hard to find the leak after pressurizing the system.
 

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check the temp sensor at the outlet of the radiator. The sensor has an o-ring which harden overtime...leadind to small leak.
Exactly what happened to my 750 , you will have to buy the actual Hose ( not the sensor) , with time it leaks right where the sensor is but the actual cause is the Lower water hose . Swapped my hose the other day and problem solved ...
 
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