sotek

When I start the car there is a rattling/ticking noise, it sounds like something is fluttering, but it's somewhat consistent so it might be rotational, but it's more of a flutter/tick noise, I'll post a vid tmrw. If I drive for a bit and make a quick stop of go through a drive through, if I put it in park or neutral, the noise is still there, but a little quieter. But that's only after driving for a bit. If it sits and I start it, it'll make the noise in Park, at normal volume (enough to be heard in the cabin!). This only occurs when it's cold, at 750 rpm.. before it's calmed down to 500rpm.. Once it's cycled down to a normal idle, it doesn't make this noise. Although when driving it seems to have some pushback when stopping around 750-800rpm, makes the rattling/ticking noise and due to the pushback always makes me lurch to a stop. It doesn't seem to be changing gears either, tranny seems very smooth. When driving, it's weird as when slowing to stop for a light, I'll be about to stop and the rpm's will hover around 750-800rpm and cause a bit of pushback and having to brake a bit harder .. it makes the rattling/ticking for the last 20 feet before the stop as it goes through this 1.5 second stagger at 750rpm when around 20 feet before the stop... then I stop, the rpm's drop abruptly drop to 500rpm.. very quickly and the rattle/tick goes away (when it's warm, it it's not warm, the tick/rattle is still there when I'm sitting at a light), it's a jerky stop because she sorta holds at 750rpm from 20feet before the stop, then drops out to 500rpm abruptly when I come to a stop. Doesn't seem to be a downshift either, it downshifts way higher.
When accelerating off the light, she's a bit slow up to about 750rpm, bit of a delay but she still starts to move, after 750rpm it's regular driving.

I'm thinking crankcase vent valves, it's like she can't breath or is getting too much air when starting and can't blow off enough when stoppings.. but then again, maybe I'm out to lunch. I haven't tried the AC Compressor test (running it to see if noise disappears), though I doubt that is it as I replaced the idler tensioner a while back thinking that was it... and the AC isn't making a noise. Upon closer inspection when replacing the idler tensioner, I noticed the sound seems to be coming from the front passenger side, top of the engine, either its the crankcase vent valve or maybe that's where the vacuum pump is?? (reading some other posts, some reference the vacuum pump as a culprit and it looks like that's where it is). I also read that there may be a recall. Would it be worth it to bring it in for a nice Stealership Oil Change and have them check for that brake booster recall (as I believe part of the recall was replacing a defective vacuum pump).
She runs nice and smooth on the highway and accelerates nice and smooth after that initial hiccup when getting going from a stop. I also thought it might be the VANOS. I've read the seals can go bad and the oil pressure doesn't hold when it's cold, might also account for when it's stopping/starting too - but I don't know enough about it (VANOS) to even conjure how it works and where the defect may be. I also read it could be something to do with the inner workings of the VANOS.. but can't elaborate much on that as I don't recall the post well.
Could anyone shed some opinions on what this might be? I don't want to start replacing random parts, already replaced one! I'm thinking crankcase vent valves, maybe vaccuum pump, maybe VANOS. It's an automatic, but perhaps there some sort of a tension spring that's worn in the clutch/tranny. I don't claim to know very much at all, so no jumping on my self-diagnosis (or lack thereof!)!

Thanks!

2004 BMW 545i

sotek

Anyone????

healthservices

When the noise happens, try pressing down on the crankcase vent valve to see if the noise changes or disappears.

sotek

I'll try that - do you think it's not seated properly or has popped off? I'm sure it's seated fine, haven't pulled either off yet.
Not sure exactly how they work, I thought the exterior was stationary and the spring and baffle inside it moved (and the baffle can break and cause the noise)

healthservices

mine made noise and stopped when I put pressure on the cap. I removed and stretched the spring a little and it stopped my noise. Dunno if it is the same noise you are having though.

ras545i

sotek, did you get your issue resolved....im having the same issue....

mag5qc

Sotek - I'm having the exact same problem, and the noise isn't getting quieter. I've lived with this for a while and my indie noticed it last visit, but it didn't warrant attention yet. Now 6mos later I am considering the rotary vacuum pump off the pass side head is creating that rotational rattling. Note that the seal between the upright solid/plastic tube junction (coming off the top rotary air pump) has blown off twice in one year indicating a problem with the pump. The noise, as you described, is clearly coming from this area. The AC pump and all other rotational parts are replaced and functional, including my sec air pump (which is located right behind the pass headlight). Next week I visit my indie and plan to rectify this noise/problem along with a host of maint items I need to perform.I'll post again after my appt next week with the results.

F-Tar

Update please.. What happened?