Quote:
Originally Posted by andrewwynn
Oh: the sound you described doesn't sound like what you think it is. It sounds like your chain tensioner is shot.
If my engine did what you just described I would park the car and order an OEM chain tensioner and replace before I turn the key again.
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Just realized I never followed up on this thread. I changed the tensioner with OEM. What a pain.
Fired it up and gave it a few moments for the tensioner to fill with oil and then restarted. Still rattled. Let it cool off a bit and grabbed my stethoscope. Listened on restart it the noise was not coming from timing chain but from valves. Talked to my indy and he had me do 3 hot oil changes after driving with Seafoam in my crankcase for about 50 miles. Did the first change and drive 100 miles and immediately did hot oil change to cheap 5w30...and I was shocked how much gunk came out (as Im religious on oil maintenance). Drove 50 miles and did another hot change....then another drive and a final change back to full synthetic 5w30.
It appears I was able to get whatever gunk was holding the ball bearing open in the check valve as the rattle is now gone. My indy also said that the o-ring can start to degrade and allow the oil to drain out of the head and cause the same rattle.
The next time we are doing any top end work, I will have the entire valve changed while I have it torn down.
07-10-2020, 10:10 PM
chain tensioner is definitely a solid bet and usually causes what you are describing, it's also a pretty inexpensive part in the grand scheme of the X5 and relatively easy and straight forward to replace, which is also another oddity for the X5 
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