Metal sound after start up
 

I started my 2003 Chevy Blazer yesterday, and it had metal scrapping sound. I tried to figure out what it is. It sound like something that would go with the rpm of the fan. I turned off to go get a flash light. When I restarted it was not there anymore. I used it last eveing and didn't come back. What could that be? Why would it disappear?

Could this be the distributor?

With all of this sub-zero temperature lately, it could be the starter drive is not retracting after the starter is disengaged. Without putting an ear on it, tough to diagnose.

This problem been around before the sub zero temp. and didn't show any problems due to the noise. The noise since 10/09 has evolved differently, on and off but always show up at start up and after a minute went away. I had my Blazar at the garage to fix the intake manifold because of a coolant leak and they found the distributor rotor needs to be replaced, because it scraping against cap. So now will I hear the noise again. Time will tell.

After a couple of days, so far I didn't hear the noise.

The sound has returned and seems to be worse. I get it starting up. Then it goes away mostly, but its like I can hear it faintly. When I start driving it goes for good. I opened the hood but have a hard time pinpointing the direction where it comes from, yet seems it comes from the serpentine belt area, but I can have a bad sense of direction of where sound come from. It doesn't sound like the symptoms of a bad water pump.

An old school trick for locating noises is to take ~3' section of 3/4" heater hose and hold one end to your ear. Move the other end around to different places. When you get close to where the sound is orignating from, you'll know it ;) You can pinpoint the source. It works for vacuum leaks, engine noises, alternator noise, belt tensioners, idler pulleys, etc. Inexpensive and low tech, but it works.

I didn't have a heater hose around, but I decided to try the to use the end of the roll of toilet paper. This evening when leaving work when I started it, it came and stayed. It was dark and had no flashlight. But the noise appeared to becoming around the alternator and idler pulley area. I drove a little bit and the noise got faster with the RPMs. Like it did in 2009, I stopped the engine and restarted again and it went away. It may be a bad bearing somewhere?

Yup, could be. Alternator, belt tensioner, water pump, A/C compressor, and the idler pulley all have bearings. Might need to use the tube from wrapping paper, tis the season! They're a little longer than a TP roll;)

they got mechanics stethoscope for $4 at harbor freight...