hi everyone i had similar problem last month when it was very cold in nyc...i was getting low coolant level message and brought it to dealer..they said it was in fact low and added fluid..they checked for leaks/problems and said they found none..sa said it is common problem in cold weather...i really didnt believe him but didnt have much choice...i forgot to check level when i got car back to see how high plunger was...i checked last week and plunger is at min level...will keep checking...rob

just to add my 2cents, diesel engine oil ALWAYS gets black very quickly, trust me i have over 1millions miles in diesels,also coolant could leak into intake manifold if manifold has water jacket,ask bmw as i had 318ise losing coolant and had to find specialist engineer to locate problem. he did "sniff" test to locate hydrocarbons in coolant although he knew it was not cylinder head gasket,it was rubber seal on intake manifold.not a major problem if using small amount of coolant but check level frequently.

amacman:

Valid point on the diesel oil. I looked at the poster's profile originally and saw it was a diesel in question, but since we got so sideways on the consistency of the oil, I decided not to bring it up back then. This thread is coming up to it's third birthday, so I was surprised to see it back. I work for a distributor of the world's largest diesel engine company, and have spent time in service management, so yes I agree completely that diesels can have black oil showing on the stick by the time you drive 1 km after an oil change. Colour isn't an indicator for needing an oil change in any engine, but that is particularly true with a diesel. :thumbup:

:D i love the big MACK V8 and especially CAT V8 diesels.

Off Topic
 

I am with you on the Cat diesels :thumbup:, but the V8 models would be my least favourite. I like the V12 and V16 models more. There are sometimes potential vibration issues with the V8s in applications such as gensets or marine. They are fine in vehicle applications.

When you say Mack, do you mean Mack trucks (not in the UK AFAIK.....) or MAK, which is now owned by Caterpillar? Gotta love anything burning distillate and producing 20,000 hp each. My own experiences with Cat engines top out with engines rated at around 8,000 hp each.

mack V8 fitted to williams F1 team renault magnum, my experience of trucks ended 10 years ago. biggest cat V8 was 18 litre,about 900bhp can`t remember torque but was 120,000kg gross tank transporter, great fun dancing solo in tractor,very scary at max wieght. weeny machines compared to stuff you mention.

I have found that I generally could smell even the slightest leak, check the cap..the dealer can pressurize the system and see if it looses any pressure, .....easy test....

Well it is nuts, prism must have had his mystery leak solved, as for mine well no joy, when I last checked the coolant level, the top of rod was at MAX level when car cold. I drove 566miles/900km approx and then rechecked and level was halfway between max and min (which is still ok according to manual) but cannot for the life of me see a where it is leaking as the leak must be so gradual. A compression test sounds good but any trustworthy mechanics out here don't have the kit, and going to bmw I know they are going to fleece me and make me worry more....another thing that is a tad worrying is I took the coolant reservoir cap off when the car was cold and there was a slight hiss of air being released....now is this trapped air being released from the last time I topped up or fumes in my coolant system?


And if the cooling system is able to 'collect' air how the hell is it letting coolant out in the first place? a top notch diesel and I have to top up the coolant..

I also suppose the heater matrix / air con channels could be leaking but that would steam up the car I guess?all is clear....

That leaves like headgasket etc etc and that worries me although got no water in my oil, if it such a tiny loss would it collect anyway or dissipate in the heat....thanks guys for all the feedback this site is a great help...and I often know more than mechanincs about the ins and outs of the x5

Prism X5 is a 3.0d (diesel engine). The "tarry" engine oil is normal for a diesel engine. The oil will go "tarry" very quickly after an fresh oil change.

I'm going to bring this up again! After about 4 months and 4000 miles (2K on a long sustained highway trip) my coolant level was down again, not much but enough to trigger the "low coolant" message periodically. This happened once before and I had topped it up with no issues. I and my Independent mechanic checked all over for a leak including pressure testing the system with nothing. His suggestion was small valley pan leak being burned up as it drives, so no leak? It's topped up and the explanation makes sense I think? I was planning on doing the cooling system soon including VP gasket. It seems there is a mysterious coolant leak alot. Could it always be the valley pan gasket?