Last year my '84 Pontiac X-car with the 2.5L duke 4cyl failed emissions testing. Heh, only had 98k on the motor and 226k on the original cat, so I couldn't complain. The car was being used as a project for my autobody classes anyway, so I just parked it. A few months ago I moved it to my shop and parked it again, it not being a priority. Last week I decided to get it back into service as a winter beater car, so I pulled the intake and exhaust off to weld some cracks and clean out the carbon from the EGR passages. I pulled the #4,3, and 2 plugs out for inspection, looked great. Had to use a 2' breaker bar to remove plug #1, and I had to use it all the way. Luckily no threads came out with the plug, though I ended up breaking off the porcelain. I used a flash- light to inspect the threads in the head and saw the bright green of coolant pooled on top of the piston. Sigh. So, I soaked up as much as I could with paper towels in the spark plug hole and shot some oil into the cylinder to slow any rust. Tonight I pulled the head and discovered that the cylinder was fairly rusted where the rings were in contact while it sat, and the top of the bore as well as the combustion chamber were also fairly well rusted with some pitting. The piston top was immaculately clean compared to the other three, however.
The other three cylinders have the original crosshatch and no perceptible ridge, the #1 cylinder has no crosshatching and has visible circumferential ripples worn into the walls as well as a pronounced ridge.
I inspected the head gasket for tracking from a coolant leak, but found none. The fire ring delaminated on this cylinder, with half stuck to the head and half stuck to the block. Near as I can tell, barring cracks in the head/block, the coolant must have seeped through the gasket material itself and through the crack in the fire ring to pool in the cylinder. The excessive wear and rust indicate that this had been a problem for a while.
The block is already .030 over, so I'm assuming that it's a goner. I'm running the head to the machine shop Friday to get it magna- fluxed, hopefully it will be ok considering that the core charge for the 2.5 head is running around $200 in this locale.
Does this assesment seem about right? This is the first engine I've ever had that had internal coolant leaking. Normally what kills my motors are bad cranks/worn out bearings. I'm assuming that with the visible ripples in the cylinder wall that honing won't accomplish much. Heck, you can see the zig-zag of the oil ring spacer spring as a black mark on the cylinder wall. :(
JazzMan