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Discussion Starter #1
Hello all.

I just brought in my 2006 z4m (s54 engine) into an independent repair shop. I believe they're pretty well respected so I won't name them for now.

Anyway, car was running poorly, occasionally dropping power, showing VANOS codes, engine light, all seemed pretty much like the solenoid bank was dying.

I just got a call- they replaced the vanos with Dr Vanos. Car started fine. They increased revs and heard valve tapping and shut it down.

They said there are plastic tension pulleys on the timing belt. One seems cracked and have tightened the timing chain to the point where the valves are hitting.

They haven't quite suggested but started talking about a complete engine rebuild.

Does these seem right to you guys? (I know enough to be dangerous but can't quite get my head around how a car with no valve tapping when it went in comes out with valve and cam damage just by putting a new Vanos in.)

Thoughts?

Thanks.
 

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I assume they mean timing chain (not belt)? There is no plastic tensioners on the timing chain. There is a plastic chain guide that is known to break, but that should not impact timing of the valves.

Timing on an s54 does not change on its own unless the timing chain breaks.. I would ask specifically what they did to “replace the Vanos”. If they did anything to the cam gears then they would have to re set the engine timing. If they did that wrong, a valve can hit.
 

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Discussion Starter #3
Robgill, thanks for the answer. Sorry, definitely timing chain.

And it could have been a plastic guide they said, though I'm all but positive they had said at the end of the timing chain.

It was the full Dr Vanos unit (not just the solenoid bank). I'm not sure if you need to do anything with the cam gears or not.
 

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Car has a chain, not a belt, responsible for timing. There is a guide that usually breaks on passenger side but that would make the chain loose and potentially skip a gear. Did they open up the engine?

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Discussion Starter #5
Sorry,I had meant to say chain.

This just happened a couple of hours ago so I'm not sure if they have opened the engine yet.

But, they we're very clear that the problem made the chain too tight. Which had the valves getting hit.

Which doesn't make much sense to me.

I'm wondering if they just screwed up the cam timing? But I'm not sure what exactly replacing the Vanos entails?
 

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Robgill, thanks for the answer. Sorry, definitely timing chain.

And it could have been a plastic guide they said, though I'm all but positive they had said at the end of the timing chain.

It was the full Dr Vanos unit (not just the solenoid bank). I'm not sure if you need to do anything with the cam gears or not.
If it's just the vanos unit, then they did not touch timing, so I am not sure where interference would come from. Did they confirm that the guide was broken?

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Discussion Starter #7
They certainly indicated that there was a guide and they break. I'm not sure they confirmed it was broken.
 

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I should say I'm pretty sure they said tensioner rather than guide. But, I think maybe there isn't a plastic tensioner at all.
 

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Sorry,I had meant to say chain.

This just happened a couple of hours ago so I'm not sure if they have opened the engine yet.

But, they we're very clear that the problem made the chain too tight. Which had the valves getting hit.

Which doesn't make much sense to me.

I'm wondering if they just screwed up the cam timing? But I'm not sure what exactly replacing the Vanos entails?
Yeah making the chain too tight would not make sense. There is a guide (the one that wears/breaks) and a tensioner which keep the tension on the chain, so not sure what they mean by too tight.

Hopefully they know the procedure and did not accidentally loosen the hub bolts (which they didnt need to in order to just replace the vanos unit). Loosening those bolts requires to reset timing properly.


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Discussion Starter #10
Anything else they could have done that would have caused the valves to tap? (other than the hub bolts)

And any thoughts on what I should do from here?
 

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Too many unknowns.
Possible they didn't touch timing, but any good mechanic would check and adjust timing when replacing the vanos unit even if they didn't loosen the hub bolts to replace the unit. If they did change timing and it's off enough, it will cause valves to hit.
A tight chain will not cause valves to hit. A loose chain, broken tensioner or guides can cause timing to jump which will cause valves to hit. The top timing guide which is the most prone to failure needs to be taken off when doing a vanos swap. If it was bad to the point where running it once caused it to break, they should have been able to see that when they took the top guide off.
It's possible the unit has vanos rattle and that's what they're hearing.
It's possible your valves are out of adjustment and they're blaming it on the vanos. When they go out of adjustment they will tap loud. Have them do a compression test. If compression is good a valve adjustment and or vanos rattle kit is all you need. If compression is off then either timing is off and you didnt bend any valves, or you have bent valves. Bent valves will require atleast a cylinder head rebuild.
These motors are noisy especially the injectors. Someone not used to the S54 sound could think normal noise is valve tap.
Make sure they reset vanos adaptations, if not I've seen cars run like Cr4p after a vanos overhaul or change.
Get more information or have a second shop look at it for an unbiased opinion

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One other possibility that comes to mind is they could have initially misdiagnosed. When you first came in the car could have had bent or burnt valves and they thought it was vanos. It's also possible it had both problems. I explained what causes bent valves, burnt valves happen for detonation, knock or lean fuel conditions. Could also be from unadjusted valves. A bad vanos unit can cause burnt valves over time but would require extensive driving on the failed unit, and cases on the s54 are super small.

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When camshafts are in proper time (questionable at this point) cranking the engine and trying a compression test often results in very low numbers.
During normal starting the DME alters the camshaft timing to bleed off compression as an aid to starting. First time I ran across this (~2000) it blew my mind.
Leakdown tests are Di Rigueur around here.

If the valves have actually hit the pistons (again questionable) I'd refrain from any further cranking of the engine with anything but a socket and a long ratchet, slowly.

Good thoughts above.
 

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Discussion Starter #14
Thanks all for the input.

As it stands the valves are visibly bent. The shop is, perhaps a bit slowly, taking responsibility.

They didn't say so exactly but seemed to confirm they had loosened the hub bolt and had not done the timing afterwards.

So, I guess the last question is outside the obvious what should I absolutely make sure they fix?

And thank you all again for the help.

K-
 

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If valves are bent you need the valves replaced that are bent, new headgasket, cylinder head might have to be machined for flatness. New valve stem seals, maybe new springs on damaged valves. While it's at a machine shop a carbon cleaning wouldn't hurt. And obviously timing needs to be set when reinstalled, new head bolts aswell

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Hopefully no piston damage. If piston damage occurred then new pistons aswell with a rehone and rings

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Hopefully they know the procedure and did not accidentally loosen the hub bolts (which they didnt need to in order to just replace the vanos unit). Loosening those bolts requires to reset timing properly.
In most cases the hub bolts have to be loosen to move the spline shafts out of the vanos in order to unscrew the LH threaded connecting the vanos pistons to the spline shafts. I think they did this and then didn't set the vanos timing correct.
 

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They didn't say so exactly but seemed to confirm they had loosened the hub bolt and had not done the timing afterwards.
Wow, the hub bolts were loosen to slide the spline shafts in order to disconnect the LH threaded shafts to the vanos, and they didn't do the timing after? Maybe they confuse with the non-M E46 which doesn't need to be timed again after r/r the vanos.

Btw, There is no way a broken chain top guide could tighten the chain. Even if something on that side (the RH side viewed by driver) cause the chain to tighten, this will not able to change the timing. The only way can change the timing is something caused the chain to be loosen or tighten on the LH side.
 

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Jesus, what a nightmare dude, I feel for you! Hopefully they will fix everything they damaged, but in the end, you have your car back, with a problem it never should have had in the first place and now all this other stuff is being replaced by the same shop who did shoddy work in the first place? I'd be scared. I'd be scared to even get the car back for fear they messed something else up.
 

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Discussion Starter #20
I think more bad luck than a nightmare.

They're a BMW specialist shop so they "should" have known what they're doing. I'm sure the shop did, maybe the tech didn't.

Anyway, they've broke it, they've admitted it was them that did it, and they're going to fix it.
Not much more that I can ask for I don't think.

Life goes on.
 
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