X6 smoking after long idle

[Shinobi87]

Hi all

Bit of a car noob so bear with us please

X6 (2013 E71 x50i) owner here. I've had the car coming up two years. After a year or so of ownership, the car started smoking after a long idle. I did a bit of research, seeing lots of posts pointing towards old hardened valve stem seals (big job - no garage I've come across has the kit here and thus naturally charging an arm and a leg to take the whole engine out). I did notice a cracked crankcase ventilation hose - hoping it was that but after getting that changed, still smoking

I failed the yearly test that they do here in the UAE due to the smoke - emissions test was fine. I bought some Liqui Moly stop smoke - I was actually after the 'oil leak stop' product but bought the wrong thing! - anyway so I chucked it in and it actually helped and reduced the smoke significantly (I tested idling for about 15 mins).

I went for a retest and unfortunately there was a queue and I had to wait 35 mins idling (its hot here so need to keep the car running for the AC!) and then it was my turn and boom, it started smoking quite a lot again !

I did some tests at home and noticed that the car would smoke more if it was warm. So I took the car to the test place again in the evening, but left it parked for a couple hours outside the test place - went shopping. Came back, took my token and didnt start the car until it was my turn. It did smoke a little but the guys passed it this time - it was near closing time also

Now I'm looking to leave the country and head back home. So that means I need to do another test as its a requirement when selling the car to a new owner ! There's nothing wrong with the car apart from this, in fact its in really good condition for its age.

So I bought the liqui moly oil leak stop product - did an oil change, 8 litres of oil, I used a slightly thicker oil this time (magnatec 10-40) as I heard that the thin oil leaks more, and then added half a liter of the 'oil leak stop' product. I've since done 1500km and its still smoking on long idles. I have seen reviews where apparently it can take 3-4000km before the product starts working.

A couple of questions please:

1. After an oil change, drove 1000km and the oil needed topping up as normal. I topped up a quart. When can I safely put more of the 'oil leak stop' product in ?
2. Are there any other ways to get around this issue without forking out for the seals change work ? The super long idles are very rare, almost to the point that I often forget I have this issue - but its come to the fore now that I will sell the car in a few months time.

TLDR - car is smoking after long idles - some success with additives but have a scenario where the car will be tested before being sold which will inevitably involve a long idle before the test - help!

Thanks for any info!

[XRatedM]

Check the PCV system check valves and O-rings, in most cases those cause blue smoke after long idle.

Failed valve stem seals will cause blue smoke on cold start as well as long idle, if yours doesn't smoke on cold start I'd suspect it's the PCV system.

[Shinobi87]

Originally Posted by XRatedM

Check the PCV system check valves and O-rings, in most cases those cause blue smoke after long idle.

Failed valve stem seals will cause blue smoke on cold start as well as long idle, if yours doesn't smoke on cold start I'd suspect it's the PCV system.

Thanks - there's certainly no smoke on a cold start so thats encouraging - having said that, I dont think I've ever given it any revs until its up to temperature.

The PCV hoses as mentioned were checked, one was replaced. The only other thing was the vacuum pump o-ring was replaced (a bmw specialist garage a year before checked my car over and said there was a minor leak - when my friend checked it he really couldnt see much wrong with the o-ring but replaced it anyway). I guess there is more than just the hoses that needs checking - I'll have to get my friend to give the PCV system a once over.

[XRatedM]

Originally Posted by Shinobi87

Thanks - there's certainly no smoke on a cold start so thats encouraging - having said that, I dont think I've ever given it any revs until its up to temperature.

The PCV hoses as mentioned were checked, one was replaced. The only other thing was the vacuum pump o-ring was replaced (a bmw specialist garage a year before checked my car over and said there was a minor leak - when my friend checked it he really couldnt see much wrong with the o-ring but replaced it anyway). I guess there is more than just the hoses that needs checking - I'll have to get my friend to give the PCV system a once over.

In my opinion, when PCV system hoses crack or leak they may make check valves fail as well. If check valves are ok, next thing to check would be oil separators that sit inside the valve covers.

[Shinobi87]

So my friend has been busy so his junior engineers had a look.

- They think they found air leaks so ordered and fitted new intakes and pcv vent hoses.

- Car is now smoking a lot more! It's constantly smoking whilst idling, previously you could only see smoke when giving it some stick after a long'ish idle. It's white smoke.

- When driving home, the CEL came on with lambda probe error messages. I cleared these and they havent returned now - possibly triggered by all the oil - there could have a bit a lot of idling whilst they were looking at the car.

- They didnt check the check valves or oil seperators.

- I needed the car urgently so I took it off them, plus I didnt want them working on it - they disconnected the battery also for no reason - the date/time needed setting again - could this have caused issues?

- This morning - I went to top up the oil as they said it was approaching near low and I had some at home - I noticed the coolant had reduced a lot, well below the min - I only topped it up about two weeks ago!

Friend has promised to have a look but admittedly not an out and out BMW expert - does this shed any more light on whether its the PCV system, or stem seals? Or is it the coolant leaking?

Started this morning and no smoke on startup.