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  #1  
Old 28-12-2014, 02:55 PM
JuhaV JuhaV is offline
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Default Vanos replacement - some DIY notes

Hi all,

Here is the background story that led me to replace the Vanos unit in my S50 powered -99 Coupe : http://www.z3mcoupe.com/forum/showthread.php?t=17316

Here some earlier analysis and attempt to summarize the Vanos procedure before I actually pulled that damn thing out myself : http://www.z3mcoupe.com/forum/showpo...82&postcount=9

I have now done some practical work with my car and the story in figures can be found here : http://v2tre.wordpress.com/2014/12/2...uns-perfectly/

In short I have :

- replaced all relevant vacuum lines that are the normal suspects for rough idle
- replaced the complete Vanos unit with a Rolls Royce factory serviced unit
- adjusted the valve clearances
- changed camshaft position sensors
- changed plugs, oil and filters

The happy outcome was that now the car idles perfectly, pulls smoothly from the idle upwards, the Vanos is much quieter than earlier and the engine seems also to be happier in higher revs.

I have owned the car from 67 tkm upwards and at idle there has always been a slight "pop" sound from the exhaust every 5 or so seconds. In addition, the engine shaked shortly every now and then when stopping at lights. It felt like the engine would have a single misfire every 5-10 seconds. Otherwise the engine worked ok and has full power. During last summer the engine first started to run roughly for about 5 seconds after a cold start. Then towards the end of the summer it did not idle any more correctly under 900 rpm. From that upward it worked ok.

Now all this seems to be history and especially the low rpm end seems to be smoother that ever :)

If there is interest, I can try to walk you through of some of the things I noticed when doing these service steps. These notes might fill in some things that at least to me were not fully clear after reading through the Beisan procedures and the BMW TIS procedures.

br, Juhav
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Last edited by JuhaV; 28-12-2014 at 03:00 PM. Reason: Some typos, engine type added
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  #2  
Old 29-12-2014, 11:43 AM
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glad you got it fixed
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Old 31-12-2014, 11:47 AM
JuhaV JuhaV is offline
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Thanks Dave ! I am very happy with result now when I have done some driving. It seems that my Vanos has been on the "edge" for a long time me not really realizing that it was the cause of those symptoms. Actually, I have taken them mostly to be something like "they all do that Sir". All the M3'a I have been riding have more or less performed alike !

It seems that the low rpm behaviour is now as it should be. Steady idle, easy take offs, AC does not cause overly high idle. Turning steering wheel when not moving does not affect the idle any more. And the sound is now clean without the mechanical rattle

Before pulling the Vanos, I changed all the hoses under the airbox and cleaned the idle adjustment valve (motor). For me, these did not have any significant effect at all. But this was because the hoses were not that badly rotten.

The takeaway from that was perhaps that I realised that some of the hoses are "behind" the throttle body butterfly valves and therefore at the "high vacuum" side when the butterflies are closed or nearly closed with small throttle openings. Thus those hoses can really mess up the mixture because high vacuum will suck air through even minor fractures or loose connections.

Then those hoses that are on the airbox side are not that critical as they would need to have bigger holes to cause a significant leak. This is because the vacuum is small on this side of the butterflies. However, they can cause problems because leaks in there will cause unmetered air to enter the engine and ECU will not be able to estimate the correct injection (or will require large lambda corrections).
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Old 31-12-2014, 12:14 PM
JuhaV JuhaV is offline
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Regarding the Vanos replacement some notes.

Putting it very simply, the removal and installation of the Vanos requires that the crank is rotated to TDC and the Vanos (and thus the camshafts) are pulled to max retard position. This the "reference" position and in this position the Vanos pistons will be fully into the Vanos unit.

The reference position can be measured and indicated using the special tool that is positioned above the cylinder head and has two pins that can be inserted into the correspondive holes in the cams. The crank can be locked into TDC using a special locking pin.

The practical problem in this that the cams are really difficult to move into this position manually. The cams have a location that accept a 24 mm wrench for turning the cams manually. However, there are two things that resist the cams from turning :

1) Vanos pistons that have oil pressure behind them. This is easiest released by removing the solenoid valves from the Vanos. This releases the oil pressure and pistons are free to move.

2) The slanted gear between the cam sprocket hub and the Vanos piston. These are intented to move when both the cam and the sprocket with the hub are rotating. If you try to rotate the cam without rotating the sprocket (=rotating the crank) the slanted gear tends to stuck or lock.

Solution for the 2) is simply to rotate the crank simultaneosly when trying to retard or advance the cam with the 24 mm wrench. If you rotate the crank in clockwise position, then the cam can be move into the same direction and advanced relative to the crank. And vice versa you can arrive into the max retard position : turn crank anti-clockwise and pull the cam to the left side of the car (seen from the front).

After some experimenting one learns how to max retard or max advance the cams and then the rest of the job is rather simple.
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Last edited by JuhaV; 31-12-2014 at 12:44 PM.
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Old 31-12-2014, 12:21 PM
JuhaV JuhaV is offline
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Beisan System gives very detailed procedure how to install the Vanos into the sprocket hubs correctly. The same is given in TIS with minor difference in details.

In short, the reason for this is those slanted gears. The hubs and the sprockets have certain adjustment area to fine tune the cam timing. When you are installing the slanted gears into the hubs, this adjustment needs to be turned fully clockwise because then when you push in the slanted gears you will end up approximately in the middle of the sprocket adjustment range. Clear enough, when you push in a slanted gear, the hub needs to turn in order the gear to move into the hub.

The hubs both in the inlet and exhaust cam are held in place with 6 hex bolts each. In the inlet hub the bolts are accessible from the front and in the exhaust hub slightly less conveniently from the back.

The main thing here is that as long as you do not loosen those hub bolts, the timing remains unaffected.
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Old 31-12-2014, 12:40 PM
JuhaV JuhaV is offline
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One final observation below.

Checking the cam timing is always done at TDC and the cams fully retarded (= Vanos pistons fully in).

The Beisan and TIS procedures explain that you always start with the cam sprocket bolts in this position where 2 out of the 6 bolts are visible. Going through the sprocket bolts starts so that you do not loosen the first two bolts (let us call these the TDC bolts) but rotate the engine clockwise so that the next two come accessible. Then you loosen these two slightly (one rotation) so that they do not hit the timing plate (especially the timing plate behind the exhaust sprocket). Then you rotate the engine again to access the next two and loosen also these. Then rotating for the next two you actually access those "TDC bolts".

Now you can set the cams and crank into the reference position with the timing tools and taking care that you rotate the engine ALWAYS in clockwise direction not to become affected in the minor slack in the cam chain.

What you can do now is that you can loosen the final two "TDC bolts" in the sprocket hubs and you may rotate the cams respect to the sprockets and camshaft with the 24 mm wrench.

I did the final timing of the cams so that I first pushed the cam over to slighly
advanced position and then pulled it back to the correct reference position that was indicated by the timing tool. The crank was locked during this by the locking pin. It is essential to approach the correct timing position so that the movement is retarding and thus against the timing chain side that does not have the chain tensioner. This side of the chain is pulling tightly and therefore when the engine is running it has no slack. The tensioner side will have some slack when there is no oil pressure to tighten the tensioner.

Odly, the above procedure to fine tune the cam timing is not explained in the Beisan procedure nor in the TIS procedure. In them, if the timing is off, you need to start from the beginning by first removing the Vanos. At least I made that interpretation and this seems unnecessary to me.

When the final two "TDC bolts" in the hub sprockets are loose, one can adjust the timing in the range allowed by the elongated "slots" in the sprockets. In the end, the correct timing is achieved very near in the middle of those slots. When the cam is in the correct position, tightening the "TDC bolts" locks that position and later allows to rotate then engine and cams to tighten the rest of those total of 6 bolts 2 at the time.

Please accept my disclaimer that I am a hobbyist mechanic and will therefore take no responsibility of the notes and their correctiviness.

However, my engine is running now nicely and I installed my Vanos according to these principles.

Happy New Year and Driving Season 2015 !

- JuhaV
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Old 01-01-2015, 12:03 PM
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Very interesting reading, I wonder if the vanos should be regarded as a service item and overhauled every xxx miles to keep in perfect running condition rather than wait for any issues?
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Old 05-10-2017, 05:49 PM
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I have recently pulled my vanos unit of my S50 motor and the unit, and sprocket hubs, are currently with Mr Vanos in Darlington for re-furbishment/seal replacement.

As re-installation approaches, I have been reading many sources online, including the Beisan Systems and BMW TIS guides and considering putting it all together without the fancy BMW 'timing bridge'. Of course, if I did this work professionally and repeatedly, there is no question that the various special tools would be worth buying, but unless I am missing something, I just can't see why they are really necessary.

Fundamentally, when timing the cams, they can only be out by at least a whole sprocket tooth. Why do I need to precisely measure the cam position? Surely I assemble the sprockets/hubs/chain (mindful of rotating the crank so that the non-tensioned side of the timing chain is tight), and the reference marks on the camshaft that line up with marks on the camshaft caps are either aligned or they are not. If not, adjust by one tooth and re-check. Yes, I also have to be mindful of the range of advance/retard movement in the sprocket slots, but I would have to do this, even if I had the timing bridge.

Once the cam timing is correct, clearly the slanted gears on the Vanos shaft must correctly align with the splines in the sprocket hubs - but again, the timing bridge doesn't really help with this.

Why do I keep on seeing people suggesting that doing the job without the bridge is impossible/foolhardy? i just don't get it.

Incidentally, it seems to be fairly common knowledge that the (exhaust) solenoid cover bolts are prone to shear, allowing large quantities of engine oil to be ejected. I have seen it stated that this happens because the bolts suffer stress fractures and that stronger replacements are recommended. Mr Vanos has told me something that I have seen nowhere else: the bolts only break because of the solenoid o-ring failure. The failure allows the solenoid to twist slightly in its housing and as the cover is machined to hold the solenoid in place, this twisting overloads the bolts causing them to shear.

My bolts sheared at low spead (curiously just following an oil change), so the oil loss was not to bad. If the shearing was to happen at high speed, the resultant oil loss could very well lead to engine seizure before you knew that anything was wrong. Uprating of those bolts would seem to be a very worthwhile and low cost option.
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