I have here a 93' Celica ST with a second gen 4AFE. Over the course of a few drives this metallic grating sound became louder. When the noise started getting more concerning I checked the oil and it was at the "low" line.
I refilled it, and it sounded better. I changed the oil and filter and the noise was quieter, but still there; and every time I start the car it is louder.
I dropped the oil pan to see if there is any bearing material, but there is no sign, not a speck of metal flake in the engine or oil, so the crank/ rod bearings haven't been spun. I found that the A/C Idler pulley is slightly loose, but I'm not so certain that it's the source of the noise. At this point I'm not really sure what it is. My concern is damage to the valves/ cams as that is the last place in the engine that the oil travels to.
Take a listen.
Video of THE SOUND [
drive.google.com]
