You never know when the next gremlin will sneak up on you. Two days ago I removed the valve covers of my engine for a quick periodic inspection.
While checking rocker arm clearance, one jam nut on the rocker adjuster was a little resistant. I had to apply very slight pressure to get the wrench on and then wiggle it to remove it. Odd. Moments later I used a torque wrench with socket to finish the adjustment. I had to wiggle the socket to get in on the jam nut. Now I was curious. Grabbed a flashlight and did a close up inspection. I could barely see the reason for the wrench's resistance to go on.
The photo is of the suspicious jam nut that I forced onto a tapered punch so we can all see the surprise. I'm glad to have found this gremlin early.
David