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Discussion Starter #1
Hi I have an issue with my car. At idle I hear a noise which sounds like it could be a tappet (it has the same rhythm/speed if slightly less metallic quality to the sound). If I apply another 100-200rpm it disappears. When the engine is warm the noise is still present but if I press the sport button which seems to every so slightly raise RPM it fades away near enough. On Youtube I found a vid with the exact same noise - they advised that it turned out to be the

"chaintensioner between cams and the V shaped sliding chainguide.."

If you want to see for yourself its M5 E39 Vanos?? - YouTube

I just wondered how common this is - the noise on mine is less pronounced than this video and sometimes almost fades away. Is there anything else this could be? I have my car booked into the main dealer for next week - when I took it to show them the car was outside by a fairly busy road and they couldn't actually hear what I meant. They were more interested in revving it and holding it on the throttle at different RPM's and basically said that it sounded sweet but I told them when they have it in the shop they'll hear it and only at idle.

Any advise would be appreciated as my worst fears are something on the engine internals - I would be happy as larry if its a chain guide/tensioner! The car is 2001, full service history, about 120,000 miles.
 

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For real diagnosis help we'd really need to hear it. Can you maybe post a vid? As with any unusual tapping sound in an engine I strongly recommend against driving the car until it's properly diagnosed.
 

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Not sure, about this... I don't think its rod bearings. It definately could be the top tensioner, or deflection reail, or the vanos not getting enough pressure... Just ideas.
 

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Your description sounds like the rattly VANOS gears a lot of us suffer from. Supposedly it's not an issue at all. Mine would do it when it idled and would go away if I turned the AC on. I had my idle revs increased by 150rpm when I got my tune done and now I can't tell you the last time I heard it.
 

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Discussion Starter #6
Thanks for the replies. I am having trouble uploading a video - will try to borrow a smart-phone and do this later (I still use an old Nokia!!)

I am assuming rod bearings are what I know as big-end bearings i.e. the connecting rod to crank bearings. That being the case, yes this one of my biggest fears but a V8 engine having done 120k would be extremely surprising - I would expect to hear this from a 250k I-4 engine maybe!!

Also big end bearing failure tends to be louder under load or acceleration - this noise is not audible under acceleration although maybe the noise of the car covers it.


The Vanos issue I have come across before - mine does have slight chattery Vanos on one side. But it doesn't sound like vanos noise - its a distinct tapping that fades in and out and disappears with a couple of hundred RPM.

Wilhit10 you suggested also this could be chain tensioner. Whats the cost likely to be if it is this (this is what I suspect it actually is) being done by main dealer? Whats involved?

Many thanks to all of you.
 

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I do not think its bearings...listen from the bottom...see if you hear it from there.

If its the spring... It all depends on how far you want to go to fix it. One spring is 150.00 and you have to replace gaskets of the valve covers etc... I know my local bmw dealer wants 1750.00 to just replace the valve covers. I know I have at least 900.00-1000.00 in my repair in just parts. Then again, I am replacing anything that shows wear. The only thing is, you have to get the valve covers off to see if its bad. My repair includes all guides, tensioners, and spark plugs etc...
 

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Bearing noise does not go away with revs.
Sounds like tensioner, or vanos noise to me, but then again - hard to tell by just reading the description.
 
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