lanejacobs84 Posted September 19 Report Posted September 19 1979 M20J io-360 A3B6 (no D) 3280TT ~1500SNEW I'm looking for theories as to why my #1 cylinder exhaust valve guide had a complete failure and started producing substantial steel and aluminum 100 hours after being overhauled in July of 2023. Backstory: I bought the plane from my Dad who has owned it since 1988 and flown it regularly and taken good care of it. I grew up in it. Last summer on my first flight I noted the #1 CHTs were climbing well over 400f. So I did a prebuy/annual and the local Hood River, OR A&P inspected and said the valve guide was out of limits as well as the rings. The cylinder was honed for resurfacing. The guide and rings were replaced. Equal cylinder fuel flow was noted and the injectors were cleaned. I replaced the baffling subsequently because none of these actions reduced the CHTs as much as the baffling did. It still creeps over 400f... Anyways, we bring it to the Troutdale Mooney Service Center a week ago and they say the exhaust valve guide is broken and loose in the head. The guide was moving up and down in the cylinder casting and now the largest oversize guide just falls into it. So it destroyed the overhauled cylinder 100 hours into its first overhaul. Frustrated to say the least. Now apparently new Lycoming cylinders are backordered for an unknown time. Has anyone experienced a failure so quickly like this? I have a few theories but am just hoping to hear any thoughts.... Thanks to this great community. Lane Quote
PT20J Posted September 19 Report Posted September 19 Premier Aircraft Engines is at Troutdale. You could have them look at it. My guess would be that the cylinder wasn’t overhauled correctly. I’d try to have Greg source another overhauled cylinder. 3 Quote
Alan Maurer Posted September 20 Report Posted September 20 I recently replaced my #1 cylinder (Continental IO550) because of very very low compression. It was sent Zephyr Hills in Florida. They failed the cylinder because of a crack and I wanted a factory new cylinder. Cannot get one from Continental either. So was aa able to get an overhauled one from them. Alan 1 Quote
A64Pilot Posted October 7 Report Posted October 7 It doesn’t sound to me like the guide failed. I think it was improperly installed, possibly not enough interference fit. Properly installed guides eventually wear out of course but should never loosen from the head. 1 Quote
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