525i loud banging knocking noise
 

Last night I drove home from about 110miles and on the way home I could hear a loud banging noise. Sounds like a rod knocking or something. I didn't drive it crazy and there are no engine lights or anything. While at idle I tried to see if anything changed if I were to take off the oil cap and nothing. Then I turned the A/C on really quick for about a second or two to see if anything changes and it didn't I was still able to hear the noise. I could hear the noise from inside the cockpit as well. I hope it's nothing drastic and it's just the A/C compressor, one or all of the pulleys/tensioners malfunctioning. Could it also be the chain guide tensioner lose inside getting hit by the chains or something? What else could it be? This sucks I was about to get the transmission checked and rebuilt with this TC ZF 5HP19 Stage 1 Torque Converter (BMW) and new mechatronics if need be. Now I might have to reconsider.

What year car do you have and how many miles. Why are you getting the transmission rebuilt? Have you checked the pulleys to make sure there was no play in them? What type of oil do use?

2004 525i e60. m54. I still haven't looked at my car yet since. I'm going to check out the bimmer tomorrow. I'm sad I really like the car I was going to get EVERYTHING replacednexcept for engine internal work. Hopefully it's nothing internally and it's just a A/c compressor or something.

Might be engine mounts? I had something similar to yours.

I now think it's the A/C compressor and pulleys. When I do turn the A/C on max the noise dies down a lot. Is there any way to disconnect the A/C compressor?

There should be a plug sitting on top of the compressor.

So I can just unplug the compressor. Should I cut the A/C belt as well until I get a new compressor and belt? Would It be ok to drive tot he A/C shop with the compressor unplugged and the a/c belt cut? It shouldn't matter if that's the problem right?

Ac compressor pulley sounds like I replaced mine 3-4 months ago. (pulley and belt only)

I'll have all the pulleys changed. My problem is getting it to the shop.

So I took all the fuses that deal with the A/C and I disconnected the ac compressor. I also cut my compressor belt and the noise was gone! Now i'm gonna order all the belts and tensioners and get that done. I also noticed my control arm is worn. That should be an easy install right?