An odd problem "Chain like noise"

[1995540i]

As you can tell I have a 540i that has just recently developed a new problem. I wish I could record the sound it makes but my only recorder is really not able to pick up the noise correctly.

Anyways, I have what sounds like a chain rubbing against something and this sound is definitely coming from the area between the rear of the engine and the front of the transmission. The sound occurs right when I start the car, accelerate, or maintain around 1400rpm. I do not hear the sound while coasting or cruising above 2500rpm. There is no loss of power, however the sound makes me believe there could be a very large problem so the car is currently parked.

Additional information, I just fixed the oil-pump bolt issue and retensioned the chain that drives the oil-pump hoping that would fix the problem, however it did not although there was 3 bolts in the pan that I had to replace.

Does anyone have any ideas about this, or have a similar problem? I was thinking it could be the flywheel making contact with something in that area, or, hopefully not, the torque converter doing something strange. I'll see if I can get a sound clip up here as soon as possible but if you have any ideas before then please share.

[BMWDriver]

I had a chain noise too, coming from the right rear. Turned out to be the handbrake cable. To test it out, I raised the handbrake a notch or two while driving, and the noise stopped when going over bumps - which is when it occured most.

If it vibrates steady when the engine gets to 1400 rpms, could it not be the exhaust system ? Check to make sure everything is tight and attached properly, from the engine down to the cat. See if there are any busted gaskets.

[Sixdown]

I get a rattle from my 5-speed transmission, occasionally, that also sounds like a chain when turning off the engine or revving it high and letting go. It's the dual flywheel in my case.

[1995540i]

Some kind of update:

Today I have inspected the exhaust system completely, no rubbing and an exhaust shop's mechanic found no issue with the exhaust system. Also I tried the handbrake as suggested earlier, which doesn't seem to be the case.

However, the local transmission shop today had a look at the car and confirmed the noise to be located right at the junction between the transmission and engine block. They told me the sound they hear seems to be a bolt that fell out and is being hit by the flywheel teeth. Which would confirm my suspicions but I'm not very trusting of non-BMW service mechanics, and this prediction doesn't really seem to follow all of the symptoms the car makes anyways.

Looks like a trip to BMW is in my very near future, anyone else have any kind of issue like this, specifically a "thunking" sound between the transmission and engine right after start-up and acceleration up to 1700rpm? It doesn't do it at idle, coasting, or engine breaking, or even slight free-revving "not about to ruin my transmission doing it too much".

Thanks for the help guys, I hate to hear bad news about my favorite car.

[Paul in NZ]

i dont agree wth bolt theory.Why would go away after 1700 rpm?.Why wouldnt it do it at idle or coasting?The flywheel always turns if the engine is running.

[MBXB]

Check your ATF fluid level?

[1995540i]

Yeah I can't get behind the whole "bolt theory" either. Just doesn't seem to make a ton of sense to me which is why I'm taking it to the BMW place this coming Monday. Also ATF fluid level is great, right at the lip just before it is completely warmed up. And as I remember correctly this problem has been long in the making, I remember an odd noise at the end of last summer which has slowly been getting worse, until last week when it started being more consistent.

I'll keep everyone updated as I get this problem solved. Hopefully the folks at BMW will be able to solve it as I'm fairly sure I know more about this car and how it operates better than any of the mechanics here locally.

[whiskychaser]

I had a chain-like noise once. To this day I will swear it wasnt coming from the front end. And so will two others. Outcome - wrecked timing chains guides and 12 bent valves. Moral - if it sounds like a chain, maybe its a chain?

[1995540i]

I had a chain-like noise once. To this day I will swear it wasnt coming from the front end. And so will two others. Outcome - wrecked timing chains guides and 12 bent valves. Moral - if it sounds like a chain, maybe its a chain?

Actually the chains were the first things I checked as well as the guides. Still can't believe how many chains are in this car. 2 short double rollers, 1 long double roller and a single roller driving the oil pump. I will still trust chains much more than belts, long story


Yeah well if it sounds like a chain but then becomes much more tinny sounding soon thereafter it's a good idea to check the catalytic converters. The converter on the passenger side of this car has melted and it's guts are making all kinds of racket rattling around the inside of its box. Which makes me suspicious of the exhaust shops ability as they could swear the sound wasn't an exhaust issue. Boy were they wrong. Anyways, cats come out Monday and I'll have a car that no longer sounds like a baby rattle. Thanks for all of the help guys, it's much appreciated.

[Ross]

Thanks for the follow up. Often these mysteries remain so to the other members and we learn nothing from your experience.
Who finally figured it out?
I find it interesting that once again the "undercar" shops proved inept. Lemme guess, franchises in both cases?