Timing chain issue ?

[raymond.harper]

Cheers guys. The noise (video early on in thread) only occurs when the engine is properly warmed up - i.e. No noise initially when gauge up to temperature, only when the car is thoroughly warm (but still in the middle of the gauge) so can't understand why that would be...?

Oil thins when warm which is perhaps why the sound occurs when the engine is warm. From the video the sound appears when the throttle has been backed off and not on partial throttle which could indicate the timing chain perhaps

 

[jnwright71]

Hi All,

I’m sure Justin will be along later, but thought I would provide an update as this is getting weirder and weirder.

Garage removed rocker cover and checked the VANOS gears, chain and upper guide. All perfect. No other signs of any issues. They then removed the filter housing (after taking out the intake manifold, again perfect working order. They did report some small metal particles in the housing though .

They them moved on to the sump and removed it. Lower guide all OK. Oil pump, pick up and gear etc all OK, but more metal particles in the sump. Garage has advised that these are probably non-magnetic i.e. aluminium or magnesium. This is worrying, although they weren’t there on either of the previous two oil changes (circa 100 and 50 miles ago).

TTBOMK, the only aluminium rotating parts are the water pump impeller and potentially parts of the oil pump. The water pump can be ruled out as can the oil pump as even if it was failing (and even if the internals were aluminium or the housing being damaged by failing internals) any debris would be captured by the oil filter and the sump would be clean.

Therefore, all I can think is that the timing chain remains slack or running out of true and it is slightly catching the block and gradually shaving off micro particles of aluminium (or magnesium). These would then drop into the sump which explains their presence.

The original master tech that looked at the car thought it was a guide or failing cam hub (i.e VANOS unit).

Does anyone have any thoughts on this diagnosis ? Pie in the sky, possible, probable ? All ideas welcome.

Frustrating ...


Many thanks, James

 

[ph001]

Water pump has nothing to do with the oil at all so I would rule that out. Timing chain seems most likely but I thought this had already been checked? You would expect to be able to see marks on the cover or block.

 

[jnwright71]

Hi,

Chain and the associated castings have supposedly been checked. However, the garage is being asked to check again and the metal particles will be analysed if required to define the metal type. The original master tech suggested that a broken or badly worn guide could allow slack in the chain that cannot be taken up by the tensioner. He also suggested that if the guides were OK, then the VANOS hub could wobble when the oil viscosity drops when the car is warm.

I just cannot see any other explanation for why a well maintained car with an intermittent engine noise could be showing non-magnetic metal deposits in the sump.

Hopefully the garage find something today.

Cheers, James

 

[Ducklakeview]

Hmm, have been watching this thread.

The presence of metallic particles is not good Do you have any pics of said particles showing the shape/size? Might help in determining how they have been removed from their original site, ie chipped/shaved etc. My thoughts are definitely timing chain related, IF the VANOS was "wobbling" it would have to move a hell of a lot to either move the chain far enough out of alignment that it catches, or for the VANOS itself to contact something as it's rotating.

I think I mentioned earlier in the thread that I have seen one Si with a similar noise coming from the oil filter area. I know the oil and filter etc have been checked, BUT has anyone fitted an oil pressure test gauge, and monitored the pressure whilst the noise is happening? If it's fluctuating, could point to either the timing chain "whipping" about (if the tensioner is oil pressure fed) OR the oil pressure bypass vale...

Just a couple of thoughts.

Also, despite it being mentioned a few times, I didn't see a definite answer to the question regarding running it with ALL of the aux belts removed, as vibrations and the resultant harmonics in rotating ancillaries can cause some strange noises.

Mike

 

[Smartbear]

I think the fact that this issue only developed 100miles after a service is a bit of a smoking gun, do you think it’s possible the car was run up without new oil being added in error & fresh oil added after the event?
It seems a massive coincidence to me
Rob

 

[jnwright71]

Thanks Mike, good points and something that the garage needs to confirm. I will have the oil tonight, so will be able to post an image of the particles tomorrow. The tensioner is oil pressure fed and is brand new.

Smartbear, thanks for the thought, but I did both oil changes myself and the car was not started until 6.5L had been added the first time and 6.0L the second time (then topped up to 6.5L after a run and gauge check). Unfortunately i think the oil change link may be a bit of a red herring.

Fingers crossed that the garage will find something soon

 

[Mike6]

I have come across particles in the sump from a breaking up thrust washer but not from a Zed. Hopefully its nothing to do with that but it can get a bit noisy when end float develops.

 

[Z4M-2006]

Has it got any crank float and the chain is touching the timing case ?

 

[Mike6]

Thats what I meant by 'end float'. A terminal diagnosis on any engine

 

[Cooky3]

Thanks for your thoughts guys. All reasonable suggestions to me as I know nothing about engines... Picked the oil sample up tonight with bits for James to provide to a mate for analysis. See what he says and go from there...

It's difficult to keep giving advice to a mechanic of 40+ years when you know nothing yourself... All I can do is keep slipping in what you are telling me here...

On an aside, when your car is away and in need of work it's amazing how many Z4's you see on the road... Literally hundreds today, and I'm sure all the drivers were flicking the V's at me! :x

 

[Cooky3]

Hi all - quick update.

I picked up the oil and 'bits' on Wednesday last week from the garage and dropped them to James who has a mate who could analyse the particles. Got the answer today. Basically black plastic at 0.3g per half litre of oil in the sample provided with one very small insignificant contaminant which has been narrowed to a likely rocker cover gasket sealant or similar. The have not been through a combustion cycle. Suggestion therefore is that it most likely came from the timing chain guides where the swarm could drop into the sump. Mechanic said they were non magnetic but a bit of difference in my head between what plastic and alloy or whatever the engine casing is made of...

Spoken to the garage and whilst they have checked the guides visually as far as possible with no obvious signs of damage they intend to revisit the area and strip / replace. Suggestion is to get the chain replaced at the same time and already have a replacement tensioner in situ.

Does this sound familiar? Everyone who heard the car (4 mechanics inc. specialists and the guy it is with) thought it sounded like the noise was coming from the timing chain area.

In addition, if the chain is replaced presumably the timing has to be redone. Can the guides be replaced with the chain in situ or will the timing have to be redone anyway? Is this a big / specialist job requiring specific tools?

If I am replacing the guides and timing chain with genuine items any ideas on approximate cost?

This is keeping me awake at night to be honest... Had the car four weeks or so and had it in my possession about 3-4 days.... End is near I am hoping...

 

[Smartbear]

That sounds strange, the garage said they were aluminium or magnesium metal particles & not black plastic particles the report has come back with?
The two would look very different :?
Rob

 

[Cooky3]

Indeed smartbear... I didn't look as I picked them up in the dark from the mechanics forecourt and it was about 10.30 when I dropped them with James (he was away on business so I left them in his driveway) and it was pitch black. I am hoping it is guide material so replacement will cure but failing that I am probably having a very expensive bonfire....

 

[Ducklakeview]

Indeed smartbear... I didn't look as I picked them up in the dark from the mechanics forecourt and it was about 10.30 when I dropped them with James (he was away on business so I left them in his driveway) and it was pitch black. I am hoping it is guide material so replacement will cure but failing that I am probably having a very expensive bonfire....

Worthwhile cutting a tiny piece off the guide that's visible with the cam cover removed for analysis/comparison? Obviously from an area the chain doesn't run in...

Mike

 

[Cooky3]

Cheers Mike. Good idea but unfortunately car is about 45 miles away, then I would need to get it to James and then onto his mate who then has to travel to get it analysed....

Going to get the guides stripped anyway on a gamble as it appears this is about the only plastic bit directly located to the sump and given the particles had not been through a combustion process this is hopefully it... Fingers crossed.

 

[ph001]

Any news on this one OP?

 

[Cooky3]

Thanks for asking ph001. Was about to update.

So, had new timing chain, guides and tensioner fitted today. Oil replaced, run up to temp and noise is still there. :headbang: Everyone thinks it was guides but there you go. For reference the vid is an earlier post here...

Spoken (via James) with a specialist. They had seen a similar issue with the same engine as mine. Customer had replaced the items I have had done and apparently it then threw the chain within 200 miles causing major issues. Apparently the repairers had not replaced or cleaned out the oil pump pick up pipe and strainer. If this is blocked it can restrict oil pressure at lower revs meaning the tensioner does not work properly... Apparently cleaning it doesn't necessarily make a difference - it should be replaced. I have spoken to my guy and whilst he has not replaced it he did remove it to check it and suggested it looked OK...

Could this really be the issue?

Other suggestion has been worn cam hub but he said any movement here would throw a fault code. There are no codes. The sensors are very sensitive I believe so this would make sense surely. For the hub to be worn enough to cause the timing chain to whip or grind would surely throw something up...

In addition the engine runs sweetly at idle and performs as it should when being driven. There is no lumpiness or issues to see or hear.

Going to perform an oil pressure test tomorrow. Interestingly he has another Beemer with the same engine as mine in the shop so intends to run an oil pressure check on that too for comparison...

I have never had so much hassle with any car or bike I have owned (and that's a lot) in my life....

He is as frustrated about it as I am....

HELP.... PLEASE....

 

[ph001]

This is just crazy. It seems almost everything has been eliminated here (I'm not going to mention running it with no aux belt again as surely the garage must be certain its nothing to do with any of the ancillaries). I just can't see it being oil pressure related with the tensioner. My head is steering me back a hva issue.

 

[Smartbear]

I would run it without the serpentine belt to discount items driven by it, quick & easy to do so get them to do it.
Rob