What is this?( on 2004 X5 E53 3.0 d Sport

[Smeeagain]

Nosing around under the bonnet I undid the cap to the radiator coolant and there is a little floating device inside - what's it for? The coolant was milky white - is this ok ? (Doesn't seem right to me)

Smee

[Junkie]

The little floating device is a simple indicator to let you know there is sufficient coolant in the system, if it pops up on removal of the cap its all good, if not then refer to the handbook to top up with the correct coolant mix.

The milky white colour doesn't sound promising, don't want to worry you but I'd get it checked out in case of oil contamination...

Is the engine running as normal, i.e. for a diesel anyway?

Also check for additional exhaust smoke and also the cooling hoses when the engine is running. You should expect some pressure in the system but if the hoses are flexing noticeably again get it checked sooner rather than later - thinking head gasket.

Good luck and let us know the outcome.

[Smeeagain]

yes everything is working fine and no smoke anywhere and hoses appear fine - I did think about the oil contamination myself .....hopefully not !

[X5Sport]

Milky coolant definitely sounds like oil/water mix in there and wants changing pronto. There should be a little plastic wing stcking out of the side of the coolant cap area with the float symbol indicator on it to tell you the level. Item 8 in this diagram:

http://www.realoem.com/bmw/showparts.do ... g=17&fg=05

What does the milky fluid smell of? If you draw some off into a glass, does it separate at all? It's just possible someone put oil into the coolant system there rather than coolant because they didn't RTFM and got the wrong hole ( if you'll pardon the expression). Seen this reported a few times on several forums over the years. BMW Coolant is blue and it used to be recommended that you stuck to theirs as it had all the right anti-corrosives and inhibitors for the alloy types BMW build their kit from.