datorres88
Daniel Torres
- Joined
- Feb 15, 2015
- Messages
- 1,296
- Reaction score
- 695
When doing my annual last month I discovered two cylinders with low compression and was able to hear air through the exhaust during the compression test, a clear indication of leaking exhaust valves. Using my friend's mid-range quality borescope we inspected the condition of the valves and #3 looked like it was possibly burnt, while all others seemed to look OK. I was going to attempt to lap the valves to see if that would fix the problem, but while attempting to do so, the makeshift valve spring compressor we had failed to do the job, so I just resorted to ordering new cylinders.
However, while attempting to lap the valves, I noticed a lot of evidence of exhaust ash on the exhaust valve spring, an indication of worn valve guides. After seeing this, it was clear to me that the cylinders would need to come off anyway. After pulling the valve covers on all cylinders I found the same condition on #2.
By the way, these cylinders are ECI Titan Nickel Carbide cylinders and they were installed about 11 years ago as a result of an ECI A.D. I had the engine overhauled only 2 1/2 years earlier and had to replace all four cylinders due to the AD. At the time I welcomed the change because ECI had prorated the cost of the cylinders so I was happy to get all new cylinders for a total cost of $700. But that was a mere 343 flying hours ago. Why would valve guides wear so soon? I would have expected to go to TBO, or at least get 1,000 hours before seeing any valve issues? Is this a problem with ECI?
So anyway, yesterday, I replaced #2 and #3 with brand new Lycoming cylinder kits. I was a firm believer in ECI cylinders because of their Nickel Carbide bores, but no more. I've learned my lesson there. I'll stick with Lycoming from now on.
So here's the $64,000 question: Which came first, the leaking valve or the worn valve guide? After pulling the cylinders, #2 looked pretty good with a nice reddish orange color and a nice pizza pie pattern. #3 had the same pizza pie pattern, but was turning greenish which would indicate that it had become overheated. Both showed evidence of exhaust gas on the valve springs. So was it worn valve guides that caused a wobble which led to an ovaling of the valve seat or was it leaking valves that caused premature wear of the valve guides? It is the chicken or the egg?
However, while attempting to lap the valves, I noticed a lot of evidence of exhaust ash on the exhaust valve spring, an indication of worn valve guides. After seeing this, it was clear to me that the cylinders would need to come off anyway. After pulling the valve covers on all cylinders I found the same condition on #2.
By the way, these cylinders are ECI Titan Nickel Carbide cylinders and they were installed about 11 years ago as a result of an ECI A.D. I had the engine overhauled only 2 1/2 years earlier and had to replace all four cylinders due to the AD. At the time I welcomed the change because ECI had prorated the cost of the cylinders so I was happy to get all new cylinders for a total cost of $700. But that was a mere 343 flying hours ago. Why would valve guides wear so soon? I would have expected to go to TBO, or at least get 1,000 hours before seeing any valve issues? Is this a problem with ECI?
So anyway, yesterday, I replaced #2 and #3 with brand new Lycoming cylinder kits. I was a firm believer in ECI cylinders because of their Nickel Carbide bores, but no more. I've learned my lesson there. I'll stick with Lycoming from now on.
So here's the $64,000 question: Which came first, the leaking valve or the worn valve guide? After pulling the cylinders, #2 looked pretty good with a nice reddish orange color and a nice pizza pie pattern. #3 had the same pizza pie pattern, but was turning greenish which would indicate that it had become overheated. Both showed evidence of exhaust gas on the valve springs. So was it worn valve guides that caused a wobble which led to an ovaling of the valve seat or was it leaking valves that caused premature wear of the valve guides? It is the chicken or the egg?
