Engine knock, broken piston

[Donald]

1988 Corolla SR-5, almost 329K miles on the odometer. It runs, but has a loud engine knock.
I finally got the oil pan down, suspecting that it was a bad rod bearing, but was quite surprised to find all the connecting rods nice and tight.
Looking up underneath, I see that #1 piston is missing a large chunk of skirt.
A quick peek into the oil pan, and there it is, or should I say, there they are......The bits and pieces of the broken skirt.

I pulled the valve cover and was astonished at how clean it is in there. It is the cleanest engine I have ever looked into. That tells me that it had been recently rebuilt, so the failing piston is probably the result of workmanship, and not materials.
The question in my mind though is, what did they do to cause this?

Lucky for me, I have a set of 4A-FE pistons and rods in a box in my storage shed.
I need to pull the head and see what the cylinder bore looks like, then decide which direction to go from here.

The plan is to get this car/engine driveable, so I can use it while I change out the synchro rings in the 7A-FE gearbox, replace some leaking seals in the 7A engine, and decide if I will keep it, or sell it and get a sedan.

I will try to post some photos soon.

[tashirosgt]

I wonder if the piston size the rebuilder used was too small for the cylinder size. Does piston "slap" break the skirts?

[eberbs1]

You would be amazed at how clean these motors stay if you do regular oil changes.
e.g: 1992 corolla 4afe valve cover pic
If you scroll down you will see apic of my motor after 270k km, its now at 354k km and im sure looks just as clean as it did in the picture.

[Donald]

Originally Posted by eberbs1

You would be amazed at how clean these motors stay if you do regular oil changes.
e.g: 1992 corolla 4afe valve cover pic
If you scroll down you will see apic of my motor after 270k km, its now at 354k km and im sure looks just as clean as it did in the picture.

Yeah, this engine looks just like the one in that photo, but there is varnish build up inside the pistons.

The amount of dirt and grime I have encountered on the outside of the engine makes me seriously doubt my first assumption than this engine was recently opened up.
I am now inclined to believe that the broken piston is a result excessive piston slap, as tashirosgt suggested.

A close inspection of the other pistons reveals cracks progressing up the sides of the skirts, that look just like the damage on #1 piston.
There is practically no indication of wear in the #1 bore, but I haven't taken a good look at the others yet so I am not sure about those. I'll have to do some measuring tomorrow to see what the condition of them really is.

Time to quit. I go to work in the morning.

#1 piston


#3 piston, see the crack? There is another one a little less obvious on the other side.