XSeries-forum

2007, X5, 4.8 M Sport, E70. Coolant level drops to the min level from max over a few short trips. No puddles under car or smell of coolant in engine bay, can't see any leaks.Do have a little white smoke though but not what I would call excessive. Are there any common places to look? I heard about valve stem seal problems, any definite way to tell if it's that? Tried the revving method and smoke but not sure conclusive. Be grateful for any thoughts.

Also worth checking the coolant cap seal. If it won’t maintain sufficient pressure you’ll get some losses.

Valve stem seals should be oil not water (I think). Any water in the oil will cause ‘mayonnaise‘ to form on the oil cap.

If it isn’t obvious then you may need a pressure test to see if everything is tight and find leaks with everything cold (such as a pinhole in a pipe/radiator etc).

Thank you, will check!

The covers would tend to hide any leaks but the water pump would be one to watch I'd think.

Thanks will have a good look around with engine running and a good torch. Just ordered some UV dye too.

Best of luck with finding out the cause. I have a similar random coolant loss mystery on mine. Got the Bimmerfix kit & water pump in my boot ready to fit as a preventative measure once I get some time.

Could be a head gasket problem causing water to leak into the engine. That could be the source of the white smoke as well as the loss of coolant.

Do not forget the black plastic header tank that the rad header cap fits to. Common for them to split along the seam and you will get a whisper leak, very hard to detect.
I had a similar problem and found the header tank was the problem.

Lez

Hi,
Thanks for all the replies, so far haven't found anything but I have now put the dye in the header tank, so will get the uv torch out and have a look at weekend. Just had the oil changed and it was normal, no mayonnaise. Will update soon.

Be careful if prodding around on the upper hoses. There are some small diameter coolant hoses connected to the top of the engine via some plastic T connectors, and these also connect to the larger pipes, again with smaller diameter plastic connection points. I think these are called Breather pipes. Sorry for lack of technical terms but hopefully you'll know what I mean.

Amongst the plethora of issues when I first got the car, there was a drip in that upper area, near the throttle body. I found some brittle parts which when prodded slightly around the leak, actually broke these plastic connections. I put it down to age of the plastics, and heat of the engine in this area. The use of plastics is ridiculous! I had to order a load of hoses and connectors, take the airbox and some other stuff out to replace them.

Hi, Thanks for the advice, I have come across one of those breather pipes already, turns out it's one for the diff, wasn't clipped up was just floating in the wind. Not found a leak yet and level is typically staying up at the moment.

may be add UV dye to coolant, it helps

Yes you are right it does help, did it a few weeks ago and found a little on the drive and a couple of lines at back of engine. Will need to remove covers etc to try and see exactly where it is coming from.
Also got a slight oil leak leaking onto manifold and causing a stink. Got some dye for that too but sort coolant first. Most importantly no sign of dye in engine oil.

Hope you find the source of the leak. These engines have common causes of leak. One is in the coolant transfer pipe in the "V" area on top of the engine. Another one (which is more difficult to get to) is behind the engine, which is another valley pan cover. Gearbox and torque converter needs to come out for that replacement, so I hope it isn't that!

V8 motor and leaks i recall all to well. Fabulous engine but not without issues as the miles increase