Cold start rattle 2-3 seconds then gone.

[BigLooga]

Hi!
Had my M3 for a while, almost 7 years now, 04 6 speed tiag/imola with 145k km, love the car.

Last year after doing a routine oil change (always put bmw 10-60 same brand) i noticed immediately after that on cold starts now the front of the engine makes a rattling noise for about 2-3 seconds and then everything is back to normal. Almost seems like there is no oil somewhere for 2-3 seconds and then bang, all good.

If i cold start the car, it rattles, then turn it off, turn it back on, there is never the rattle. This rattle happens pretty much every cold start, no matter the temperature outside.

I beleive i read back then on m3forum that this was a vanos rattle but i cannot find the post as m3forum is down and can't seem to find exactly my issue here.

Vanos is stock, good power everywhere, no sign of issue other than the temporary cold start rattle.

Anyone ever had a temporary rattle on cold start that went away?

Thanks.

[Redline]

Upper timing chain guide/tensioner.

[Shonky]

Won't be regular VANOS rattle I'd say. That happens as VANOS changes timing I'm pretty sure - you hear it during the VANOS timing test.

[Arith2]

Tensioner would make sense to me. Those guides can break as early as 30k miles after replacement.

[BigLooga]

I did think about the tensioner, i called a couple of shops and it seems the tensioners are all back order... sacidou.

Wierd story i had the exact same problem with my 03 540i and the it is a known problem that the tensioner and timing chain guides can fail at higher mileage. I had the exact same issue and i changed the tensioner (it seemed it was the stock 03 tensioner) and did not fix the issue but when i performed an oil change the problem went away.

So It is kinda the reverse with the M3, if the oil wasn't so damn expensive i would probably change the oil again just for the hell of it. My oil levels are all fine, right on the mark.

[sapote]

The main chain tensioner has a check valve to keep the oil in there, and for any reasons if oil leaked out during long hours of engine off, then lose chain will rattle until pressurized oil filled up the tensioner. One can remove and check the tensioner or leaking oil issue.

[BigLooga]

Makes sense Sapote. There is no exterior leaks, do you know if the check valve inside the tensioner is something that can be repaired if damaged or i'd be best replacing the tensioner? Thanks.

[jet_dogg]

Lol no, need to buy.

[sapote]

Makes sense Sapote. There is no exterior leaks, do you know if the check valve inside the tensioner is something that can be repaired if damaged or i'd be best replacing the tensioner? Thanks.

I don't remember exactly how to access the check valve, but I think once the plunger is pulled out then you can see the check valve by following the oil feeding hole on the side of the tensioner body.

[BigLooga]

I got around installing a new timing chain tensioner, it did not solve the issue. The install was kinda of a bitch to install as you need a specific 32mm socket so i had to customize my socket (chop it about 1/4 inch). The old tensionner was the original one (2004) and maybe it was not faulty but it was definately stiff and had almost no play in it anymore. The noise does seem to come out out of the top of the engine, almost near the vanos but it's hard to diagnose as it only happens on cold start (8 hours between starts) and only lasts about 2-3 seconds then it's gone. I will continue the search.

[Mr.wReckless]

IDK but if it sort of is VANOS oil pressure but not the usual VANOS rattle then maybe it's worth looking into changing the VANOS oil pressure accumulator? Relatively easy DIY.

[Cmamainer]

I have this same issue, have changed the chain tensioner, accumulator and did the full Beisan vanos rebuild. Only does it on cold start, sounds normal on warm startup?

[BigLooga]

I have this same issue, have changed the chain tensioner, accumulator and did the full Beisan vanos rebuild. Only does it on cold start, sounds normal on warm startup?

I see. Yes, for me it only happens on a cold start (overnight or 8hours lets say). I have changed the tensioner, it did not solve the issue, i just changed the oil last night and today will be my frist cold start since, I doubt the oil has nothing to do with it but it was just wierd that this happened after my last oil change.

[BigLooga]

Ended up doing my first cold start after oil change and the problem is still there but maybe a little... Meh, i'll update if it worsen or gets better out of the blue as it did appear out of the blue also.

[Arith2]

It either sounds like something is getting starved of oil or takes a second to settle. I would check that main tension guide. Sadly the Vanos has to come out to see it but it's probably broke. Something like a clogged filter could be stopping the Vanos from getting immediate oil pressure. Have you gotten your exhaust hub squared away or is everything still stock?