'91 325i with a stock m20b25 engine.
noise: http://junkyman.org/tmp/e30clatter.mp3
or http://junkyman.org/tmp/e30clatter.wav
This is loudest if I put a stethoscope around the crankshaft end behind the crank pulley under the car. If you analyze the waveform, it happens every 103 ms, or 580 times a minute. The tach shows 700 rpm. There is also a sequence of 3 knocks, where the first is loudest, the second is in the middle, and the last knock is quietest.
You can hear this.
I tried a few things and nothing made the noise go away:
We tried disconnecting spark plugs one at a time. We removed the fan and fan clutch. I verified the valve adjustments. The speed goes up with the revs, but at 2k+ it is muffled by normal engine noise. If I slip the clutch in 5th gear to put some load on the engine, there is no change. A/C on or off, no change.
I am absolutely stumped.
This doesn't happen when the car is cold. It is unsteady at first, then becomes very solid when the car gets to operating temp. It can't be heard inside the car with the hood down unless the windows are lowered and you are listening for it.
History:
100 miles / 3 weeks ago, I replaced the oil pan gasket, timing belt, timing belt tensioner, water pump, clutch, pilot bearing, oil, oil filter, coolant, all external seals and gaskets, giubo, csb, had injectors rebuilt and flow-tested, some other minor stuff I can't remember. Did not touch any crank or rod bearings.
70 miles / ~10 days ago, I got gas.
10 miles ago / 5 days ago it started overheating at traffic lights (not into the red, but 3/4 there), and I replaced the aux fan switch (which wasn't the problem), and discovered the thermostat was in upside down. It didn't seem like it should matter, but somehow it did. There could have just been air that wasn't bled. Anyways, once this was done, the gauge was in the middle and all was well.
5 miles ago / 4 days ago, I drive a few miles, no noise (was at operating temp), drive home, heard the noise for the first time.
The clattering doesn't happen until the engine is at normal temperature. It doesn't seem to be any accessories.
noise: http://junkyman.org/tmp/e30clatter.mp3
or http://junkyman.org/tmp/e30clatter.wav
This is loudest if I put a stethoscope around the crankshaft end behind the crank pulley under the car. If you analyze the waveform, it happens every 103 ms, or 580 times a minute. The tach shows 700 rpm. There is also a sequence of 3 knocks, where the first is loudest, the second is in the middle, and the last knock is quietest.
You can hear this.
I tried a few things and nothing made the noise go away:
We tried disconnecting spark plugs one at a time. We removed the fan and fan clutch. I verified the valve adjustments. The speed goes up with the revs, but at 2k+ it is muffled by normal engine noise. If I slip the clutch in 5th gear to put some load on the engine, there is no change. A/C on or off, no change.
I am absolutely stumped.
This doesn't happen when the car is cold. It is unsteady at first, then becomes very solid when the car gets to operating temp. It can't be heard inside the car with the hood down unless the windows are lowered and you are listening for it.
History:
100 miles / 3 weeks ago, I replaced the oil pan gasket, timing belt, timing belt tensioner, water pump, clutch, pilot bearing, oil, oil filter, coolant, all external seals and gaskets, giubo, csb, had injectors rebuilt and flow-tested, some other minor stuff I can't remember. Did not touch any crank or rod bearings.
70 miles / ~10 days ago, I got gas.
10 miles ago / 5 days ago it started overheating at traffic lights (not into the red, but 3/4 there), and I replaced the aux fan switch (which wasn't the problem), and discovered the thermostat was in upside down. It didn't seem like it should matter, but somehow it did. There could have just been air that wasn't bled. Anyways, once this was done, the gauge was in the middle and all was well.
5 miles ago / 4 days ago, I drive a few miles, no noise (was at operating temp), drive home, heard the noise for the first time.
The clattering doesn't happen until the engine is at normal temperature. It doesn't seem to be any accessories.
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