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TIL a customer's old trick for finding a vacuum leak
A guy in our shop in Phoenix showed me how to use a propane torch, unlit, to hunt for intake leaks on his old Ford truck. He just cracked the valve and moved it around the gasket seams, listening for the engine RPM to change. Has anyone else seen this method work, or is it too risky?
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jamiehayes5mo ago
My uncle used that trick on his farm in Iowa. He'd use a can of starting fluid instead of propane, spraying little bursts around the manifold. It's definitely a real thing, the engine speed jumps when it sucks in the extra fuel. Seems a bit sketchy with an open flame nearby though.
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kim_mason555mo ago
Oh man, that brings back memories. My grandpa did the exact same thing with his old tractor, using ether to find a vacuum leak. It worked every time, but yeah, watching him do it always made me nervous. You're right, it feels like you're just asking for a flashback right to the face.
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mila_murphy4mo ago
Seems a bit sketchy with an open flame nearby" is an understatement. My buddy Tom tried that on his old F-150 in his driveway, used a lighter to check a hose. The whole intake manifold lit up like a torch for two seconds. Lucky he didn't burn his eyebrows off, just singed the arm hair a little. He never did that trick again after that.
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max_patel15mo ago
It's a classic trick for a reason, but modern engines really don't like it. That extra fuel can wash down cylinder walls and damage oxygen sensors. A can of propane or even a smoke machine is a much safer bet these days. The risk of a fire or hurting the engine just isn't worth the old school method anymore.
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