I'm looking for the source of chunks which locked up my oil pump. The motor is a 302 from a '77 Mustang, although it is in a '65 Fairlane. The engine was rebuilt 10 years ago, 43K miles ago. I'm going into lots of detail below because it helps me think through the problem. Perhaps you can enlighten me on some points.
Here's the whole story. A week ago I took the car out for a drive. Two or three blocks from home, the oil light came on. I pulled over and checked the oil level, it was two quarts low (I've been neglectful of maintenance, I guess). I called home and my son brought me two quarts. I added the oil and started it up, but the oil light stayed on. I drove the car home slow, backed it in the garage (lifters were clicking by that time).
I pulled the distributor, drained the oil, and dropped the oil pan. The oil pump drive shaft was twisted and sheared. The pump wouldn't rotate. On disassembly, I found black chunks in the gaps between the rotors. There was a smashed chunk compressed in the tightest spot between rotors, but it wouldn't smash any further so the rotors locked up.
Chunks aren't supposed to get through the pick-up screen, so I looked closely at the screen. There was a gap, under the "button" at the center of the screen. In fact, another chunk was stuck in the gap, it was slightly too big to fit.
In the bottom of the pan there were a few chunks, not much.
I cut open the oil filter, there were no chunks there.
There were two kinds of chunks in the pan - hard, black, glassy chunks and black crumbly chunks. I think the crumbly chunks were cork or RTV from the oil pan seal. I don't know what the hard, glassy chunks are.
The chunks in the pump were of the hard, glassy variety. They are brittle, perhaps 0.050-0.070" thick. There was a large chunk in the pan, same thickness, oddly shaped, perhaps 0.250" square. What's wierd is it has some curvature, like it is from a piece of a broken glass tube about 3/4 inch diameter. These chunks can be broken fairly easily; they don't crumble but they shear when you twist or press them or poke them with a dental pick. There is no damage to the pump because the chunks are softer than the rotors.
The chunks are not pieces of piston rings, nor pieces of metal or actual glass. On the large chunk, on the outer surface, under a magnifying glass the surface has light scoring in the circumferential direction. The corners of the edges look like they may have been sharp at one time, but had become rounded. The corners of the chunks in the pump were sharper.
Evidently, the chain of events started when I accelerated with a nearly-cold engine (its 50 degrees in Phoenix these days) and with a low oil level. Did this make it easy to pick up chunks? Did it generate the chunks? Why didn't it eat the chunks sooner? Either the chunks just now dropped into the pan and got sucked up, or they've been there a while and just now got sucked up, maybe because the hole in the screen just now opened wide enough, or the chunks just now got small enough to fit throught the hole in the screen
I could get running again by replacing the pump drive shaft and the pick-up tube and screen to get a screen having no holes, but this doesn't eimininate the source of the chunks. Will there be more chunks?
What kind of chunk is shaped like a piece of curved glass? Did it come from under the valve covers? From behind the front cover (in the region of the cam drive)? I can't imagine it came from the clinders, because these chunks would not fit the clearance between cylinder and piston.
Are these chunks a coating of some sort, perhaps building up over time and finally breaking loose? Nothing inside the surface of the oil pan looks like this, nor does anything in the bottom of the block or cylinders. Maybe they fell off the surface of the valve covers or some other surface. I can't see inside those covers unless I remove the covers or get a boroscope.
So, any tips?
Mike