Hey folks, my '93 has recently developed a loud and scary knock. I have been scouring this and other forums to try to figure out if I'm dealing with a head gasket problem, an injector issue, an oil cooler issue, cavitation or something else I don't even know about but nothing seems to sound exactly what I've got going on. The knock is seemly random at idle but more frequent and louder at higher rpms/under load (I attached a video). I can't really tell if it seems top end or bottom end (maybe louder from the bottom?). Other symptoms were low coolant, though I just topped it up (maybe a gallon) and after driving around for 10 miles no noticable change. It is possible that the cooling system has a small leak that I haven't noticed and is low for that reason. No bubbling or other signs of pressure into radiator when run with the cap off. Heat still works. There is a fairly strong steam out of the oil filler when running, but its been like that since I got it 50k miles ago. It is smoking (greyish) even once warmed up, not much at idle but stronger at higher rpm. The smoke doesn't smell like antifreeze. The oil level has been constant and doesn't look grey on the dipstick but I haven't drained it to see (I'm being cheap, I JUST changed it). As far as driving goes, no noticable loss of power and it starts right up. I just did an injector test by turning off the key while driving downhill at ~1600 rpm and the knocking persisted with the key off. I think the next thing I'll do is pull valve covers and see if anything looks wrong under there. What else can I do? Any thoughts on a possible diagnosis or what to try next? Well, can't seem to upload the video... This is a 1993 idi with 220k miles, injectors and pump done at 180k. It has a banks sidewinder on it.