Installed a Carrera oil cooler,
not noticing that it had a plastic plug in the hole for a thermostat which I wasn't planning on using anyways. Heck, I didn't even know the Carrera cooler had a thermostat.
After "everything" was buttoned up and filled with oil, I started the car and let it warm up. Then I take it for a spin. I get a block or two away from home and notice some smoke from the right rear side of the car. Pulled over for a look, only to find oil coating the entire right side of the car! Quickly get back home and find oil blowing out of the hole where the plastic plug was.
I pulled out the cooler and went to Curry's, where they fitted the cooler with a plug and crush washer to seal the thermostat hole.
All of this happened during the morning that I was planning to drive to Mid-Ohio.