Last Saturday we were out at the hangar to inspect the 12 for a small coolant leak. After pulling both the top and bottom cowls off, the following was noticed:
The black tie-wrap had apparently been installed at the last annual to hold the oil line in position that passes under the crankcase and over the muffler. It had been installed around the oil line and the rubber coolant hose that joins the elbow coming from the cylinder to the elbow coming from the coolant pump. Apparently the tie-wrap was not installed quite tight enough. Sometime in the last ~40 hours of operation the tie-wrap slipped forward off the rubber coolant tube and came to rest on the aluminum elbow coming from the cylinder head. Because the OD of the aluminum tube is much less than the OD of the rubber tube, the tie-wrap was very loose and freely vibrated against the elbow. (The tie-wrap was moved aft for the picture).
As shown in the picture, the result of the tie-wrap vibrating against the elbow was a chafed groove in the aluminum approximately .020 deep. The decision was made to ground the aircraft until the elbow could be replaced. Thankfully the elbow is fairly inexpensive and the repair will not be too extensive. However it is scary to think what could have happened if the tie-wrap had ground its way through the entire tube wall.
The lesson here is that the plastic components we use in our aircraft are harder than the aluminum ones. Plastic wiring connectors, tie-wraps, and even wire insulation will slowly chafe aluminum components if not properly restrained, resulting in possible electrical systems failure and compromising the strength of the aluminum component it chafes against.