bent valves!?!? I keep these in my toolbox to remind me of that time with the M20 and $hit falling out under the car and leaving a trail of parts behind me as I pulled over.
but now that I have graduated to a timing CHAIN, how do these tensioners "wear" out? is there some kind of seal inside or something? to me it looked like a super simple metal on metal cylinder. What would cause it to not hold oil pressure to the extent that it loses 50% or more of its tensioning strength? Some type of wear obviously.
ok...to answer my own questions I am now in another damn BMW rabbit hole of research.
1. looks like the original tensioner (P/N 11311404438) has been superseded by 11317838675. Arguments abound but there is
anecdotal evidence that on the original design the oil feed hole is too small relative to the oil discharge hole. Not sure I believe that BMW was that egregiously screwed up. Scroll down to F1004fun's post.
2. Neither of the part numbers above is listed for any X5 model on RealOEM.
3. the 8675 part is actually the S54 tensioner and is
listed by FCP as an "upgrade" over the original part. Pelican Parts also tentatively lists it as an upgrade.
4. the original replacement is damn near impossible to find as a single piece.
5. the aftermarket parts are all on backorder.
6. appears as though you can order the Genuine cylinder, piston and spring and roll your own "Original" tensioner for a lot less than the single original part, which is available nowhere which, and seems like is basically NLA.
7. I find this entire topic interesting. It implies in a way (given that BMW went away from its original design) that it's possible, although not proven, that lots of us have been potentially living with super mild chain noise in various forms that maybe we shouldn't hear, but consider to be the norm. In my case it's a bit extreme but i'm going to start listening for it on my younger motor.
So you are left with only a few choices.
a. replace the spring in the existing tensioner
b. build your own original tensioner
c. upgrade to the Genuine S54 tensioner (if you can find it)
d. wait for the aftermarket parts to come off backorder
This sounds like a 'grab a couple of used ones at the junkyard and see if either makes any difference...then get the real thing later if it works' type of situation.