E39 540i-6 .... cause for concern ??

[VivP]

Seems it might be time to haul out the cheque book, but I'd like to at least try and find out what I'm in for first.

My E39 540i 6-Speed has developed a nasty habit. She's decided to start smoking, against all my protests that smoking is bad for my (bank balance) health! But she seems to be an "occasional smoker" ... let me explain.

If I am cruising along a main arterial route in town, 5th gear, 80 kph, all is good. Red traffic light ahead, I am faced with two options when coming to a stop. Firstly, engage the clutch and coast with brakes to a standstill. When I pull away at the green light, all is fine. Second option is to drive "normally", that is power off, gear down the cogs, applying gentle breaks, and then engaging the clutch just before stopping .... in a cloud of smoke that smells it comes from an Iraqi oil well. Pull away from the green light in a similar cloud of smoke.

My question is, why the difference? Do different problems have different effects? What is the most likely cause of mine? I was thinking, and I'm quite possibly wrong, that it is either valve stem seals or rings, or both.

Any help or advice is appreciated.
Thanks.

 

[Cole]

the fact that gearing down while coming to stop (whereas if you coast it is fine) I definitely think indicates you have a problem...

 

[Major]

Time for a compression and leakdown test. How's your idle?

 

[Raybimmer]

IMHO if you gear down and the car is under compression you will get oil in the cylinders through worn valve stem seals/valve guides , will also be a bit of smoke when you then pull off . If you drive normal and accelerate and the car smokes it is rings as oil is passing and getting burnt .
A compression test needs to be done .Do a compression test on a warm engine on all cylinders and record the readings , now put 10 ml or so oil in each cylinder through spark plug hole and repeat . If pressure readings increase then rings are being sealed by oil on top and rings/bore are worn .

 

[rick540]

Check your PCV valve.

One thing I can tell you about these V8's is the rings and stem seals can be completely wrecked and it still won't smoke in any visible way.

Something's up