Timing chain issue ?

[ph001]

I just listened to the video again. The fact that it's over such a narrow rpm range just makes me think it's something resonating...which would fit the fact of no drop in performance or error codes. You say the vanos has been thoroughly inspected and given the all clear....there really isn't a great deal left. If this does go away with the aux belt removed, somebody needs a good kicking

 

[Cooky3]

He's checking that tomorrow too but everyone who has stood in front of it and listened with sound sticks / tubes have all said its coming from the timing chain area... Including me, James and three engineers including two BMW master techs....

Seem to recall people sticking eggs in leaky rads etc back in the day. I might just drop one into the engine for good measure... :?

 

[MACK]

I've seen the oil pickup get clogged up on more than one 2.0 N42 engine when the timing chain tensioner has been at fault and the guides have been breaking so its definitely possible.

 

[Boris]

Ok; I know my way around and engine (a generic one that is) I know nothing specifically about the Z4 mechanics.

But I had exactly this same sound on an "old" 47 year old to be precise, car of mine last year or at least the vid sounds the same.

Does the Z4 have a mechanical or electric fan?

Mine was the plastic fan blade hitting something, I had been resting on it while I tried to access a remote part and bent it; now as the current car had just been serviced prior to the sound appearing, has a spanner or other tool been left inside the bonnet dropped down inside near a belt and is rubbing???? This is what it sounds like to me.

Purely coincidental, but my wife's car was in for service a month or two ago at a main dealers, I went to top up the water the other day and found a spanner laid inside the engine bay. :thumbsdown:

Just thinking laterally as they say

I really hope its not something as simple after all this trouble, but people do seem to go for the expensive stuff before ruling out the cheaper fix it would appear, by people I mean the "specialists".

 

[1000rr]

Sounds like a heat shield loose or metal cable/shroud and is resonating at certain rpm frequencies .... you’ve changed everything it could be by now.

 

[jnwright71]

Hi All,

This continues to be a mystery. However, the one common here is that every mechanic (professional or DIY) that has looked at the car has said timing chain related, and the plastic in the sump can only be there due to guide damage which must be related to guide failure or chain tension.

When Justin called me today to advise that the car was back together but no better, and having banged my head against a wall for 5 minutes, I called another BMW specialist with lots of Z4 experience. His diagnosis is as Justin has outlined, with two secondary options, but both are oil pressure related.

His main view is that the plastic swarf in the sump will have been picked up by the oil pump and could be partially restricting the pick up pipe and / or strainer. This is resulting in the tensioner being unable to hold correct tension at low RPM, but at higher RPM, the pump is pulling more oil and hence building sufficient pressure for the tensioner to operate correctly. This makes a great deal of sense to me and would explain why the noise only occurs when the engine is hot and oil thinner.

I was under the impression that the belt had been removed when the engine was hot, but from Justin’s post this appears not to have been done, so agree this is a major fail if it does stop the noise. I doubt it though, as the plastic in the oil points clearly to the fault, unless of course this is just bad luck and a completely separate issue.

The other issue that the guy mentioned today is VANOS hub rattle, again linked to low oil pressure resulting from a partially blocked pick up or failed oil pressure switch in the filter housing. However, both should throw fault codes.

Hopefully, the oil pressure check tomorrow will clarify the issue. Again, not sure why this wasn’t checked earlier, but hey ho ...

Hopefully light at the end of the tunnel.

Cheers, James

 

[Cooky3]

Cheers gents. Re. The spanner or fan blade, it's not there when cold, nor when the temp gauge is up to temp, only when the engine is fully warm still showing normal temp on gauge.

Heat shields all checked too. I did read about an engine mount guard or something. But let's not lose sight of the plastic swarf in the sump, apparently only source would be the timing chain guides....

 

[ph001]

Ok, oil pressure should give us some good information. Keep us posted.

 

[Cooky3]

Here we go then for those interested.

Oil pressure checked today from cold all the way through to operating temperature - I believe it was noted around 50psi / 3.3 bar (give or take). Is that about right? My guy has a 3.0 six pot BMW in his workshop currently (not with the same issue incidentally). Ran a pressure check on that and the two were almost identical, mine being very marginally weaker.... Full timing chain, guides, tensioner etc all done as posted and timing all spot on (he cant believe how sweetly the engine ticks over and runs).

Had to park car out the way to do another job. Came back to it and tried another idea. They started mine up and used an extendable bar to hold the revs at around 1200ish where the noise is apparent when coming on and off the revs. No noticeable noise from cold when held there. They let it run up to temperature, and as the engine got to a certain temperature the noise kicked in.... WTF is going on? How can it simply kick in when the timing gear is rotating at a constant rpm when it gets hot?

The guy has also bought an infra-red camera to apparently check for hot spots in the engine (for worn parts etc that would run hotter apparently - not sure how much people know about this). There was no obvious or specific areas that stood out.

He has been around the engine with a listening stick / screwdriver or whatever and thinks the noise is resonating within the engine but hard to pinpoint. He has held it on the sump and thinks it is audible down there but cant quite tell. He is apparently borrowing a tool that you place on different parts with varying settings which you can listen to remotely from the car to see if that gives any clues as you are away from the general noise of the car running....

He is doing me a favour and trying to fit this work in around other specific jobs to keep costs down for me and reckons he has spend about 15 hours on it to date (but at this stage says he is looking at c8 hours chargeable plus parts).... My car has been there for 4 weeks on Friday - the time is not an issue as it is supposed to be a weekend fun car; how ironic!

Should I just give up and stick in a second hand engine? Who has got one? How much? because this is like chasing ghosts.....

Or shall I just get rid and put it down to experience? (rhetorical really).

To be honest, I cant have many more sleepless nights over this debacle!

 

[Smartbear]

So did he run it up after removing the belt?
Rob

 

[Cooky3]

Hi Smartbear.

I mentioned this to him again today and he is going to do that tomorrow because I have asked him too again but he is adamant this won't make a difference. If it does it will be an interesting conversation!!!

This guy worked for BMW back in the day and used to work on the a c schnitzer cars too. Difficult for a technical div like me to give him advice.... He has already been through the oil filter housing for instance because I asked him too based on feedback here... No issues found...

Nightmare..... :thumbsdown:

 

[Ducklakeview]

Ok..

So I assume the tool he will be borrowing will be something like my Steelman Chassis Ears? I used them to diagnose which lifers were noisy on [ref]Jamie_z4[/ref]'s friends 3.0Si when I was doing a diagnostic on it for the noise.

TBH, if he's only "reaching" out for that sort of specialist listening equipment at this late stage, having already replaced parts and not cured it, I'm afraid I would be questioning his ability to ever identify and fix whatever is causing the issue..

Just my 2p..

Mike

 

[Ducklakeview]

Hi Smartbear.

I mentioned this to him again today and he is going to do that tomorrow because I have asked him too again but he is adamant this won't make a difference. If it does it will be an interesting conversation!!!

This guy worked for BMW back in the day and used to work on the a c schnitzer cars too. Difficult for a technical div like me to give him advice.... He has already been through the oil filter housing for instance because I asked him too based on feedback here... No issues found...

Nightmare..... :thumbsdown:

And THIS ^^^^ I would consider one of the first things to check when getting a strange noise/vibration that is only present at specific loads/speed - Harmonics in rotating components can cause all sorts of anomalies, so it's good diagnostic procedure to eliminate them as the cause early on.

Mike

 

[Cooky3]

Cheers ducklakeview.

I know what you are saying. Already ingrained in it. I think they have reasonably good knowledge but I am lost.

Any ideas on holding the revs and no noise cold / then noise when warmed up?

 

[Ducklakeview]

Cheers ducklakeview.

I know what you are saying. Already ingrained in it. I think they have reasonably good knowledge but I am lost.

Any ideas on holding the revs and no noise cold / then noise when warmed up?

James rang me the other night about it, to be honest I wouldn't want to guess without hearing it first hand..

Mike

 

[Cooky3]

Fair enough matey.

Everyone who HAS heard it said timing chain guides....

NOT!

Will keep you all posted. Pleased it's not costing me stamps every time I post something. Can't afford them as well...

 

[ph001]

Both vanos timing and valve lift are adjusted with engine temperature so maybe not entirely surprising, even though I know you say they have checked these two areas.

I really feel for you, these things can be incredibly frustrating. I wouldn't give up though as you must be very close to nailing this.

 

[jnwright71]

Hi Justin / All,

My two penneth. There was plastic in the oil, it shouldn’t have been there, so the guides MUST have been an issue. They have been replaced, but the noise has not gone. So, either the guides were an issue but not causing any noise and by coincidence they have been found to be failing or the chain catching, although the garage is adamanent the old ones were perfect, or this issue isn’t resolved.

Learned folks, what about;

- VANOS hub. Oil pressure related I know, but what if .... (this was the other thing the original master tech suggested)
- Tensioner. I don’t believe this was replaced again with the chain and guides, although was just before. As this is oil pressure driven, I assume it can reset itself if it has run at its widest setting, but is this the case ?


Justin,

Did Colin check oil pressure car v car when the noise was apparent ? I’ve read the demand on the oil pump is highest just above tick over when the VANOS system creates its highest demand. If the strainer/pick up is slightly blocked, then low revs would be the area in which the pump may but be able to deliver sufficient oil pressure. He says yours was slightly lower, but what is slightly, and is slightly enough to cause this ?

I still believe, based on what we now know, this is chain tension related and oil pressure at certain rev ranges may be the issue. I don’t know what is an acceptable oil pressure for this engine, but Colin must be able to find this out.

Let’s hope he finds something tomorrow and whilst it would be good news, I really hope we haven’t been through this pain for a belt tensioner or pulley, something I know you have asked him to look at since Day 1!

James

 

[Z4M-2006]

So..

Are we saying there was plastic in the sump but this was NOT from the chain guides?

 

[ph001]

The other thing that definitely does change speed considerably when the engine is warm is the water pump. Obviously no way that can be related to plastic in the oil, but the pump runs at quite a low speed until the engine reaches a certain temperature then does a step change to a much higher speed, although it doesn't correlate very well with revs so it's a bit of a stab in the dark really.

I would have thought the listening gear directly on the pump would confirm / and or pull the electrical connector off briefly when it's rattling to see if it disappears. An easy, cheap test that can be done just to continue eliminating things.