Took me SIX Hours to find a vacuum leak on a Cessna 172

Was tracking a rough running engine at work last Tuesday in Denver. Turned out to be a tiny crack in a plastic fitting behind the firewall that only showed under load. Spent half the day chasing fuel and ignition before someone suggested the vacuum system. Has anyone else had a simple issue hide for way longer than it should?

2 comments

2 Comments

miller.avery1mo ago

Tiny crack in a plastic fitting that only showed under load" - oh man, that hits close to home. I spent three days once trying to figure out why a generator on a old pickup would cut out after running for 20 minutes. @taylor82 I feel your pain on the mouse nest too, found one in a air filter housing that was blocking half the flow. Turns out a vacuum leak can mimic so many other problems, it's ridiculous. I ended up swapping a carburetor and two fuel pumps before someone older and wiser told me to check the vacuum line. Six hours sounds about right for that kind of torture.

taylor821mo ago

My buddy spent a full Saturday chasing a misfire on his old Scout before finding a mouse nest in the intake.