What other issues it will start? Is the option to change the valve lift not there to make it possible to diagnose if the issue is in valvetronic etc? Readed this from one local forum.

Check the lower vanos solenoid on my n62 the timining chain has gone bad and eaten upp the solenoid. Dont ask how this is possible... p0021 error code and missfire on random cyl.

I've been informed people for years to replace your chain tensioner regularly else this sort of thing will happen.

Would that have happened from pulling the vanos out without "parking" (forgot the actual term) the vanos previously? What I mean is advanced the chance of damage.

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Chains tensioners and guides was done about 30000 km ago according to the papers and reciept that followed with the car, what happen with the tensioner that can cause this sort of damage? I work as a mechanic and I can´t se how its possible that the tensioner can stretch the chain without breaking. it must be a couple och centimeters longer now than before.

Now I have to replace both timing chains guides one solenoid etc...

The only reason I can see is that the chain has strechted or some of the links broke. Perhaps as previous post wrote that the tensioner gone bad but I can´t se how.

N62 misfire
 

Chains don't really stretch. A 180,000 mile chain from an M62 I measured about 8-10mm longer than new (less than 1/2%).

Tensioner loses tension allows the chain to slap around. It's how the M62 chain takes out the guides. The N62 has one piece guides that are more robust and much shorter chains using two vs one.

I haven't looked into the exact geometry to explain the example above but usually the chain won't start "chain sawing" through the engine until the tensioner stops working and enough slap builds in the chain to tear out the guide and then the free slip of the chain becomes inches vs mm.

It was quite a pressure from the chain on the vanos solenoid, nearly impossible to get it out. Can´t imagine that it´s the tensioners fault but it can be bad chains.

When it´s time to do som work on it I will find the fault and let you all know.

N62 misfire
 

Tensioner will stop providing tension. At this point the chain gets loose and "whips" think of a bull whip but made out of steel and pushed by unlimited force of the momentum of a V8 engine!

Pretty bad to fail so quick: was the tensioner OEM? I've seen non OEM I sent right back because the design didn't even LOOK similar no way it would function the same. After that one example and helping rebuild several engines that had internal destruction I would never use a non OEM tensioner.

I'm not familiar with the geometry of the N62 but did the chain "derail" and jump off track of the guides to get onto the solenoid?

There is no chance the chain from N62 is 2cm longer than new. The apparent extra length comes from guides getting chewed though usually. In rare occasion that will be followed by the chain actually coming off a toothed sprocket. At this point usually very quickly chews through the chain covers, a jam and breaks the chain and some bent valves.

Oh: loss of oil pressure due to low on or pump failure will cause loss of chain tension also.

I havent looked at it yet but my guess is poor quality on the chain, have seen some with failed chains earlier but not on a bmw. Im going to remove the valve cover and timing cover and inspect what could have gone wrong here.

On the m62 the chain can get longer if it chew up the guides, but on the n62 I dont know.

It has not "derailed" because it ran just fine except from chains rattling and out of spec on the timing (kinda obvious) and a bit rough idle, I checked vanos solenoid to start with because they could get clogged and found that issue with chain chewing threw the solenoid.

Getting my hands on the car this weekend to inspect what has happened. Hopefully something easy but I think I have to replace chains, guides, tensioner etc...