Engine tapping/rattle under light load in 545i
12-16-2012, 04:07 PM
#12
12-16-2012, 04:09 PM
#13
I may be off track here but you description sounds like my 05 545. Long story short, take sound cover off the top of the engine to expose the intake and the fuel rail. Using a long screw driver or other device touch the fuel line at any point like a stethoscope. If that is the sound it is the pulse of the fuel system. If true you can hear it at idol but most notably between 1K to 2k RPM and beyond with aggressive exceleration. If so No Worries!
12-19-2012, 08:17 AM
#15
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Senior Members
Whoa, that thing sounds like an old Yugo! Just kidding. 
You definitely have something wrong, but it is almost impossible to diagnose from listening to a recording made from inside the car as the noise gets muffled by the cabin sound deadening materials. I listened with a quality set of headphones to your YouTube recording, but the quality of the microphone used to record the sound also makes a big difference. A $250 studio microphone as compared to a phone mic, is no contest.
My first impression is an exhaust leak, but again, because you recorded from inside the cabin it is impossible to isolate. Unusual noises while the car is not moving generally fall into three categories; exhaust system, engine internal (lifters, valves, lack of lubrication, failing spark plug or ignition coil, gas quality and octane, etc.) and engine external (transmission, pulleys, belts, belt tensioners, alternator, water pump).
You need to get the car up on jackstands or a lift and then have someone work the accelerator like you did in the recording while moving around, checking under the hood (across top of engine), under the car (bottom of engine, transmission and front end of exhaust system), and at the rear of the car (rear end of exhaust system) to see if you hear it more distinctly in any one location.
If it is engine internal you may see a slight difference with a different oil but it will be minor. Don't trust what the previous owner said. Change the oil if you haven't already, and change it from now on every 5000 miles or 200 hours of engine operation, whichever is less. Oil is cheap compared to problems caused by loss of additives and oxidation of the oil, which leads to lubrication failure, sludge, etc.
If the previous owner used the BMW CBS (condition based service) to determine when to change the oil you may well discover that the noise is due to lubrication starvation in a section of the engine due to sludge. If he used the car primarily to commute to work in stop and go traffic then he put a lot of hard hours on the oil compared to miles driven, which is why hours of engine operation is so important.
Isolate the noise first and then you can determine the next step.
You definitely have something wrong, but it is almost impossible to diagnose from listening to a recording made from inside the car as the noise gets muffled by the cabin sound deadening materials. I listened with a quality set of headphones to your YouTube recording, but the quality of the microphone used to record the sound also makes a big difference. A $250 studio microphone as compared to a phone mic, is no contest.
My first impression is an exhaust leak, but again, because you recorded from inside the cabin it is impossible to isolate. Unusual noises while the car is not moving generally fall into three categories; exhaust system, engine internal (lifters, valves, lack of lubrication, failing spark plug or ignition coil, gas quality and octane, etc.) and engine external (transmission, pulleys, belts, belt tensioners, alternator, water pump).
You need to get the car up on jackstands or a lift and then have someone work the accelerator like you did in the recording while moving around, checking under the hood (across top of engine), under the car (bottom of engine, transmission and front end of exhaust system), and at the rear of the car (rear end of exhaust system) to see if you hear it more distinctly in any one location.
If it is engine internal you may see a slight difference with a different oil but it will be minor. Don't trust what the previous owner said. Change the oil if you haven't already, and change it from now on every 5000 miles or 200 hours of engine operation, whichever is less. Oil is cheap compared to problems caused by loss of additives and oxidation of the oil, which leads to lubrication failure, sludge, etc.
If the previous owner used the BMW CBS (condition based service) to determine when to change the oil you may well discover that the noise is due to lubrication starvation in a section of the engine due to sludge. If he used the car primarily to commute to work in stop and go traffic then he put a lot of hard hours on the oil compared to miles driven, which is why hours of engine operation is so important.
Isolate the noise first and then you can determine the next step.
12-19-2012, 08:25 AM
#16
Thanks! I think I need to pull the belts and run it to narrow it down. I know on other cars I've had bad idlers/tensioners that sounded like a lot more. I changed the oil on Sunday. I'm going to do the plugs this weekend.