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 Broken Valve Spring in Continental or Lycoming aircraft engine
1. Corrosion
The most likely cause for a broken valve spring is corrosion. A spring under constant stress and is very
susceptible to breakage from small corrosion pits. The environment inside the rocker box is corrosive.
Not only do you have water from condensation but also combustion byproducts. This is one reason why
valve springs should be 100% replaced at overhaul. Whenever you remove valve springs from a cylinder
, look at the coils very carefully for any corrosion pits. Replace them if you see any pitting.
2. Exposure of valve spring to excessive heat.
Possible this could cause breakage if the springs were also collapsed from excessive heat.
see Collapsed and Weak valve springs
3. I suppose that if the valve springs start resonating they could break although I've never seen this happen.
You would also see a lot of polishing and contact rubbing between the coils.
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