Low coolant level, but no warning light

[newX3user]

I have a 2004 X3 3.0 . I have read about the previous postings about coolant issues, but I still think I should ask this question. I check my coolant level according to the red stick once a month and I always find it at the minimum level when the engine is cold. I refill it with a 50/50 mixture to bring the stick up to the maximum level. One month later it is again at the minimum level. The warning light does not come on, there is no smell in the cabin, and no leaks under the car. Actually there is some leak under the car, but it looks like water. Anyway, is it normal for these cars to lose some liquid during one month?. (from maximum to minimum)

[Weasel]

L:ikely have a very small leak somewhere. With most small leaks the coolant mainly leaks when engine is hot and never makes it to the ground. Look all around engine closely for aigns of dried coolant as it leaves a slimy "snail trail" at the leak, which turns to a crust residue after fully dried. Another common point for a small leak of this nature is the coolant temp sensor at radiator outlet. It is on the lower radiator hose right at the radiator. The built on o-ring leaks after some years pass.

[bece13]

Have the same issue on my X3 as Weasel described (O-ring on temperature sensor).
Is there a place were I can get just the O-ring or do I need to buy the whole sensor.
I asked the local dealer and they told me that I have to buy the whole sensor. Is it true?

Thanks,
Marius

[Weasel]

The dealer can't get just the o-ring separately, but when mine started leaking I did some playing around and figured out that a fuel injector o-ring works just fine! You can go to the local autoparts store and just pick up a fuel injector o-ring for just about anything. Like a 93 mustang, 87 F150, 01 BMW 325i, anything with bosch style multiport fuel injection.

[bece13]

Excellent. Thanks Weasel.

Regards,
Marius