Originally Posted by x5Alpine (Post 1184611)

It isn't making any noise but at the mileage they will need to be done.

Originally Posted by andrewwynn (Post 1184614)

That is a myth. having had done this operation twice. i can say with confidence it can be avoided.



Almost always the chain guides fail when the tensioner fails. People do not recognize the symptom and wait too long until it self-destructs.



In the past year, I helped somebody catch it just in time; his tensioner failed and he told me what the symptoms were I told him shut off the car ASAP and take off the oilpan to confirm no bits of plastic, then get an OEM tensioner and save your engine from certain disaster.



If an M62 shows signs of a weak tensioner do not drive that car another 30 feet. park it right there and iff needed TOW it and i'm not kidding. I've saved 2-3 M62s that would have absolutely shredded their chain guides within a week of discovery of the tensioner failing.



Here's why:



The chain on the M62 chain is stupendously long and the bottom section is maybe 3 feet and weighs a couple pounds; if the chain is not properly tensioned, when you hit a bump simple momentum will cause the chain to come off the plastic chain guide shoe and snap back with tremendous force*; by about 140-160,000 miles they are as brittle as a rubbermaid bin at -10F; they will shatter into tiny shards… but if you keep the chain tight I've seen M62s with 300,000 miles on the original chain guides.



*think of like sniping wrist with a rubber band but a 4# rubber band being tensioned with GOD only knows how many # force and moving at how many MPH around the engine timing gear!



If i had an M62 I'd maybe go the first 100-120k miles on the original tensioner but after that; maybe 60, 50, 40 K miles… as the time scale will make the guide shoes only more and more brittle, so closer together to maintain maximum tension. The shoes really don't wear; as long as the oil pressure is high enough to maintain the oil film layer that does the lubricating the chain never really touches the guides other than the first few seconds of startup.



*never* use a non OEM tensioner; $1200 in parts and 30 man-hours labor is why.



So what are 'the symptoms':? If you hear a new noise at startup that correlates to oil pressure building… here's an example; i have M54 and when I have enough new oil on my driveway, I can either measure the diameter of the spot to decide if it's time to check the dipstick *or* i can simply count the seconds on a cold start for the lifter tick to subside.



The chain tensioner is almost identical to an hydraulic lifter; absolutely ingenious actually, so the exact same reason my lifters stop ticking after the pressure builds on a cold start up and takes longer when oil is low, will cause the chain tensioner to take longer and longer to build up the force to properly tension the chain either when low on oil or just worn out.



so; if like me you hear some lifter tick on start and especially when low on oil but suddenly one day you hear a metallic slapping or grinding sound that seems to go away right about when the lifters stop ticking, nearly 100% chance your chain tensioner failed.



It could last like that for months before you hit that magic pothole that does you in *or* you can preemptively replace the tensioner and get an M62 to last a quarter million miles on the original chain guides; i've come across about ten of them online, and most of them are because 'that new strange sound' was properly investigated and the engine was turned off until it was figured out.



Sadly most people 'figure this out' when the engine quits after the chain derails and catches on something solid, breaks allowing the cams to freewheel and destroy half the valves (still recoverable it's not much more work to replace all the bent valves when you are already far enough into the guts to change the chain guides).



So… if looking to buy and M62, I definitely recommend listening very closely to a cold start, using an endoscope to look into the timing chain through the oil fill and ask if the tensioner was ever replaced to the owners knowledge.



They can be found..



*and* if the guide are shot but the chain never broke; it takes $2-3000 off the value of the car. If you are in the mood for a kind of fun DIY, go for it it's very rewarding to get that engine to start once you get it back together. (ps don't forget to plug in the fuel line to fuel rail). I plead the fifth.

Originally Posted by andrewwynn (Post 1184614)

So what are 'the symptoms':? If you hear a new noise at startup that correlates to oil pressure building… here's an example; i have M54 and when I have enough new oil on my driveway, I can either measure the diameter of the spot to decide if it's time to check the dipstick *or* i can simply count the seconds on a cold start for the lifter tick to subside.

The chain tensioner is almost identical to an hydraulic lifter; absolutely ingenious actually, so the exact same reason my lifters stop ticking after the pressure builds on a cold start up and takes longer when oil is low, will cause the chain tensioner to take longer and longer to build up the force to properly tension the chain either when low on oil or just worn out.

so; if like me you hear some lifter tick on start and especially when low on oil but suddenly one day you hear a metallic slapping or grinding sound that seems to go away right about when the lifters stop ticking, nearly 100% chance your chain tensioner failed.

Originally Posted by x5Alpine (Post 1184666)

The X5 has actually had the tensioner replaced at around 130,000 miles. It still does have startup rattle but that is all vanos.

Originally Posted by x5Alpine (Post 1184666)

The X5 has actually had the tensioner replaced at around 130,000 miles. It still does have startup rattle but that is all vanos.

Originally Posted by timmyc (Post 1184641)

Does this also apply to the N62? This is my first X and V8 BMW, so I have no prior experience with V8 symptoms/noises.



BTW, fantastic insight!