Now you may say I've not looked properly but I can't see much about this...

My friend works for BMW and said that at my mileage best thing they'd do on a 540/x5 is change the chain tensioner to protect the chain guides as its an hour job vs a days job and a headache.

I googled this and all the BMW forums seem to recommend this and claim that start rattle etc can be reduced...

I'm wondering if there is a diy for the ff on here for it and if anyone has any real world results?

Well, seeing as you asked, read this,
http://www.beisansystems.com/procedures/m62tu_vanos_procedure.htm

It's huge, but basically scroll down to the bit you need with this picture.


Read how to install just this piece, ignoring all before and after procedure. This is if you are doing your vanos seals...
Anyway, yours is an easy job,
15 mins later, you are done.
Take great care, drawing it out, it is spring loaded, it will pop out, and you don't want the sliding part falling into engine.
Same on replacing,
You are buying the sliding bolt, and Spring.

If you've got a rattle it's worth trying it first. If you haven't got a rattle don't bother.
I changed mine ages ago to try and iron out a slight knocking at idle that disappeared on reving and now, since I've changed it, I get an occasional start up rattle too

The design has changed on the tensioner over the years and I don't think the new design is much better to be honest.
It is a hydraulic tensioner which is spring loaded, the idea being the spring assists on start up when the oil pressure is low or not initially there (drained out). Over the years the spring weakens, the chain stretches and the guides wear so the tensioner reaches it's limit leading to rattles. There is also an o-ring that seals the oil supply to the tensioner, if that is leaking then oil won't pump up the tensioner sufficiently.

I seem to remember the new tensioner spring seemed weaker than the old one I removed although it did extend a bit further.

So the old saying of 'if it ain't broke, don't fix it' applies very much here in my opinion. If you are getting rattles that are due to a faulty tensioner then a new one should sort it. If the rattles are due to other components worn then a new tensioner won't fix anything.

Hi weejock

I get a 2-3 second rattle on startup then she purrs all day long so was looking to this first then the vanos return valve if not?

Yeah that's the same as me now...after I put a new tensioner in lol!
It only happens to me if it's been left awhile and I guess any oil might have drained out.
I'm not certain if it's the chain or the VANOS on mine either as both can be effected by oil draining out, as you say by the VANOS non-return valve. I tried the tensioner first as it's an easy change if not a little awkward to get to.

All I can say is if it's rattling it's worth trying the tensioner as a first easy option but don't expect miracles!
VANOS return valves I think they can be done buy just removing the VANOS solenoids and extracting from within by a bolt but that's going from memory, I haven't tried that yet as I'm planning on ripping the whole chain and VANOS out and rebuilding it.

How many are there the guide is confusing shows one but mentions multiple?

Any idea correct part no?

There is the main timing chain tensioner which you access from the outside of the timing case and takes up the main slack of the chain. The others mentioned would be the camshaft timing chain tensioners which sit inside the timing case in between the camshaft spockets, you need to strip everything down to replace those and they don't usually cause problems.

LR part number for the main tensioner is 8510259
You also need a new crush washer for it which is RYX000020

I got mine from Island 4x4 which seemed to be the cheapest at the time but obviously feel free to shop around.
http://www.island-4x4.co.uk/timing-chain-t...27431.html
http://www.island-4x4.co.uk/timing-chain-t...27432.html

there are two non return valves, one behind each vanos solenoid. fairly simple to do. i think you use an allen key to extract them. (carefully)
there is one cmain hain tensioner, as mentioned.
there is one main chain, and two smaller camshaft chains. only worry about the main chain.
there are three guides to replace. (on main chain.) and if you are doing it, change the small chain tensioner guides too. but they are not really troublesome, but could be brittle. (top of engine) these smaller ones are cheap, but affect your total bill.