Cold start rattle 2-3 seconds then gone.

[BL92]

Have you tightned the timing chain tensioner bolt hidden behind the thermostat? these back themselves out and may cause timing chain noise along with an oil leak

[sapote]

I'm not sure if the 'anti-rattle kit' is needed here, but we'll see.

I would not touch it if the shaft has zero axial plays when rocking back/forth by hand. It's not a plug-and-play process but you have to lap the disk or the cylinder spacer to get zero plays and no binding.

[Andratch]

ANOTHER UPDATE:

I took the car to a different shop yesterday who I felt had much more skill around advanced diagnostics. They took a look at the vanos and did some pressure tests - they strongly suspect that the problem could be the Vanos Accumulator. It's nitrogen gas-charged, and over time the nitrogen can leak out (even without the diaphragm tearing). The purpose of the accumulator is to give a boost of oil pressure to the Vanos when the oil pump isn't providing enough. If mine has lost its gas charge, the vanos oil pressure drops down while the car is off and it doesn't have proper oil pressure for the first second of cranking and startup.

There's not a good way to test the function of the accumulator, and while it is technically serviceable, you have to mail it out to a specialist and that takes time. So we're going to replace that and see if that addresses the concern. The part should arrive tomorrow, they're going to change it out and crank it up on monday and see what happens!

[ac427]

ANOTHER UPDATE:

I took the car to a different shop yesterday who I felt had much more skill around advanced diagnostics. They took a look at the vanos and did some pressure tests - they strongly suspect that the problem could be the Vanos Accumulator. It's nitrogen gas-charged, and over time the nitrogen can leak out (even without the diaphragm tearing). The purpose of the accumulator is to give a boost of oil pressure to the Vanos when the oil pump isn't providing enough. If mine has lost its gas charge, the vanos oil pressure drops down while the car is off and it doesn't have proper oil pressure for the first second of cranking and startup.

There's not a good way to test the function of the accumulator, and while it is technically serviceable, you have to mail it out to a specialist and that takes time. So we're going to replace that and see if that addresses the concern. The part should arrive tomorrow, they're going to change it out and crank it up on monday and see what happens!

Hi Andratch, Unfortunately, when I changed my very old vanos accumulator and it made no real difference to the operation of my vanos. The guy who repressurises them told me my old accumulator was only half full.

The accumulator is actually there to make sure there is always enough pressure for vanos operation rather than to provide a boost.

I don't wish to sound negative but i thought you would appreciate another owner's experience.

Does your vanos setup pass the DIS Vanos test?

All the best with a resolution to your issue.

[Andratch]

Hi Andratch, Unfortunately, when I changed my very old vanos accumulator and it made no real difference to the operation of my vanos. The guy who repressurises them told me my old accumulator was only half full.

The accumulator is actually there to make sure there is always enough pressure for vanos operation rather than to provide a boost.

I don't wish to sound negative but i thought you would appreciate another owner's experience.

Does your vanos setup pass the DIS Vanos test?

All the best with a resolution to your issue.

No worries, we're all in the same crappy boat fixing this problem - it's just getting to be an expensive endeavor! I see mixed reviews on the accumulator - I saw a youtube short (that I can't find again unfortunately) where a guy with a e39 M5 had a similar vanos sound, and changing the accumulator fixed it. Then other posts where it seems like it's almost the vanos version of an appendix....just an added expense uselessly sitting in a corner. We'll see how it turns out, but I'm hopeful.

I don't know if it passed a DIS test - I'll check with the shop. They're a reputable place, I've known the owner for 15 years - they did at least recognize that it wasn't timing chain tensioner

[maupineda]

The accumulator wont make a difference, its nitrogen pressure provides a pressure reserve that pushes oil from the accumulator to the VANOS unit, this is to maintain a constant 115bar internal pressure at all times in the VANOS unit, it would be most useful during multiple on and off throttle applications where the pressure provided by the pump would drop as it actuates the piston, the accumulator would provide back up pressure to ensure there is oil at pressure for the next timing adjustment.

You can test your accumulator by hooking a pressure gauge to the VANOS, run the engine, and shut it off. you should see pressure drops from 115bar gradually, as the pressure from the accumulator is sent to the VANOS unit, but after a minute or two it will drop completely. if you do not have a working accumulator, the pressure drops rapidly or instantly. I tested this in my own car as the pressure in the system dropped instantly, that drove me to change the accumulator to have the system in spec, but it never made a noticeable difference in any manner other than pressure drop speed after engine shut off. After changing it, pressure takes time to fully drop to zero.

[6speedS54]

Do you have all the bolts in the reinforcement plate? I was missing one and had a rattle when starting.

[Andratch]

Do you have all the bolts in the reinforcement plate? I was missing one and had a rattle when starting.

What’s the reinforcement plate?

[6speedS54]

The aluminum plate underneath, it has more than a dozen bolts attaching it, I would check if all bolts are there. The attachment points are metal, if one is missing the plate could be rattling against the mounting point behind it.

[Andratch]

The aluminum plate underneath, it has more than a dozen bolts attaching it, I would check if all bolts are there. The attachment points are metal, if one is missing the plate could be rattling against the mounting point behind it.

Oh yeah. Unfortunately that’s not it for mine. We had it off while we were doing diagnosis.

[Andratch]

Another Update -

Got the car back today with a new vanos accumulator, and unfortunately y'all were right - no dice. The shop acknowledges that it's an annoying sound, but that it doesn't appear to be anything that is a "grenade waiting to pop." I asked them if it could be rod bearing trouble since mine were just replaced prior to the sound starting, and they agreed that rod bearing nose typically does not go away after 1 second, and is usually a slower tick (half speed of the top end).

At the end of the day, I do think that this is VANOS related somehow. But I've thrown about $2k at this problem so far, and need to put it on hold for a little bit. The car will be stored for the next couple months, so I'll do somethinking and diagnosing while it its sleeping.

For those with this sound, it seems the next item on the chopping block is rebuilding the vanos unit itself, which I'm told is less than $1k...anyone want to take it on and report back "for the greater good?"

[maupineda]

You can try a different oil grade. 0w or 5w flows much better for cold start, a good mid point in my opinion is a quality 5w50 grade. Look for a high HTHS number with at least 1k of zinc and phosphorus content and you are good to go.

I tried 0w40, 5w50 and 15w50 M1, the car has been happiest with the latter but I do not live in a cold climate. If I were my choice would be 5w50.

10w60 is too thick and takes longer to warm up in my experience. I also don’t track the car and the M1 oils have high HTHS numbers which is what you need for high rpm use.

Edit: with 15w50 the cars does heat up in about 5 mins to 75C, good enough to use the car with confidence, also in hot climate (35-37C) in a canyon run the oil temp remains at 100C, and cools down to 90 if I relax very quickly. With 0w40 I did notice I could run 110-115C in hot days, that is why I chose 15w50. it also flows better at cold than 10w60 despite the 15w rating. I also use Ceratec for piece of mind and maybe some extra protection during cold starts.

[Andratch]

You can try a different oil grade. 0w or 5w flows much better for cold start, a good mid point in my opinion is a quality 5w50 grade. Look for a high HTHS number with at least 1k of zinc and phosphorus content and you are good to go.

I tried 0w40, 5w50 and 15w50 M1, the car has been happiest with the latter but I do not live in a cold climate. If I were my choice would be 5w50.

10w60 is too thick and takes longer to warm up in my experience. I also don’t track the car and the M1 oils have high HTHS numbers which is what you need for high rpm use.

Edit: with 15w50 the cars does heat up in about 5 mins to 75C, good enough to use the car with confidence, also in hot climate (35-37C) in a canyon run the oil temp remains at 100C, and cools down to 90 if I relax very quickly. With 0w40 I did notice I could run 110-115C in hot days, that is why I chose 15w50. it also flows better at cold than 10w60 despite the 15w rating. I also use Ceratec for piece of mind and maybe some extra protection during cold starts.

I live in southern Texas - summers are about 38C, 'winters' are about 7C. That said, the car is in an enclosed garage that stays pretty warm, and I have no issue letting it warm up for a minute before driving cold.

I *just* put brand new BMW-brand 10W60 in it from FCP, but I'd be open to trying something else...of the weights you mentioned, do you have a weight and brand of oil that you'd recommend for my temp ranges? Car won't be tracked.

[maupineda]

Sorry, by M1 I mean Mobil 1, those grades are readily available from even Walmart. They are really inexpensive but good. I change oil yearly and drive not more than 3k a year. I would start there before dumping more money. Give your climate conditions, avoid 0w40

[Andratch]

I'm still worried it could be a 'bottom end' sound. A shop replaced my rod bearings earlier this year (amongst other service items, so it's been hard to nail to one thing), and the sound has appeared since then. I'm wondering if they've failed, as I hear a noise north of 2k rpm consistently. Can't hear it when the engine is under load, but i also have an exhaust and turner intake so it could be drowning it out.

IMO, The noise sounds more consistent with the tempo of bottom end (1:1 speed, not double speed like top end). You can hear it at 8-13 seconds and 28-31 seconds in my video below.

https://youtu.be/M651aTLfZ_g

I took a sample of the oil that was in it over the couple hundred miles I drove since the rod bearing change. I'll send it off to blackstone and see.