Snapped a spark plug wire on a Cessna 172 and learned a new trick

Last Wednesday I was doing a routine 100 hour on a 172 at KAPA and the number 3 wire just came apart in my hand. The old silicone boots were baked on and I pulled too hard. Grabbed a pair of needle nose pliers and a heat gun, warmed the boot for 30 seconds, and it slid right off without breaking anything else. Has anyone dealt with those stubborn Champion wires on older Continentals?

4 comments

4 Comments

morgan_king368d ago

Actually those are Slick wires, not Champion. Champion makes the plugs. Slick magnetos and harnesses came on most 172s after the 80s. The wires themselves have a carbon core that breaks down over time. Heat is the right move but you gotta watch the temp. Too much heat and the silicone sleeve shrinks up and cracks. I keep a little dielectric grease on the boots now during installs. Makes the next 100 hour less of a fight.

ryanm608d ago

Yeah the dielectric grease tip is a lifesaver, I do the same thing now after ruining a wire on a 172 last year.

taraross8d ago

Oh man, the carbon core thing is such a sneaky problem. I had a set of Slick wires on a 182 that looked fine on the outside but the resistance was way off, ended up chasing a rough running engine for two days before I figured it out. The heat trick works great but I always use a heat gun on low setting and keep it moving, you know? Just enough to soften the boot without cooking it. And yes, dielectric grease in the cap is non-negotiable for me now. A little dab on the plug end too honestly makes the next removal feel like butter instead of wrestling a frozen boot off.

jakeb818d ago

Chasing a rough running engine for two days" oh I felt that in my soul @taraross. I did the same thing on a 172 once, swapped plugs, checked timing, and it was just those stupid carbon core wires acting like they were fine. Dielectric grease is basically cheap insurance at this point, I even put it on the spark plug threads sometimes just to make future me less annoyed.