Bill.Peyton
Well Known Member
The Sticking Valve Syndrome
I thought I would post this in the RV10 list since it applies to the IO540 D4A5 typically installed in the RV10, although feel free to move it.
About a week ago I noticed a slight miss/stumble during climb out. This occurred twice, but not on every climb out. It would only occur for a split second during the climb out, but did not occur during the cruise portion of the flight. Along with this symptom, during normal cruise I noticed a slight vibration that felt similar to a prop just slightly out of balance. You could see it in the glare shield. I downloaded the EFIS data from both occurrences and examined it looking for signs of something amiss. I knew the exact time of the anomaly, but it did not show in the data either because the sample rate was to coarse (1Hz) or it was not enough of an event to show up in the EGT, CHT, FF, FP etc.
After reading another post of a catastrophic valve sticking in an RV10, and then thinking back to another aircraft I owned with a Lycoming 360 having experienced a severe valve sticking. The more I thought about it the more I became was convinced that this too was sticking valve. Lycoming has a service bulletin addressing the inspection of the exhaust valve guides at 400 hour intervals, SB333C. I decided to perform the Lycoming Service Instruction No. 1425A which provides a suggested procedure to perform the action. Mike Bullock has a great write up with photos in this post http://www.vansairforce.com/community/showthread.php?t=128673 . I had all the tools including the ream from the last time I performed this task over 10 years ago on the 360.
I was correct in my assessment. Cylinders 3, 4, 5, and 6 all showed evidence of a very slight "interference" fit" and would not pass the Lycoming wobble test. The .4995" ream required a little coaxing to get started in the guides, cylinder 5 was the tightest. I completed the operation on all six exhaust guides in about 9 hours and flew it the next day.
With the 360, I religiously add TCP, a lead scavenger, to the fuel every time I fuel up. I put an additional 1400 more hours on the 360 without any issues, then replaced the engine at 2100 hrs with a Lycoming OH and have flown another 1200 hours without issue on the new engine. I'm going to start using the TCP with the 540.
After 2 hours over 4 flights I feel confident the issue was indeed the beginnings of the sticking valve syndrome. I will be flying a long trip on Monday and hope to report a continued clean bill of health.
Here are the stats on my engine and operation:
- Factory new D4A5
- 411 hours since installation
- Magneto ignition
- 90% of time accumulated is cross country
- All X/C flights are run LOP
- Phillips XC 20W-50
- Camguard additive
- CHT's never allowed to exceed 400 deg.,normal ops I see 310-360
One thing to add to this is that during the break in period I had a high amount of oil consumption. This continued through around 50 hours before it stabilized at a Qt. every 15 hours.
I thought I would post this in the RV10 list since it applies to the IO540 D4A5 typically installed in the RV10, although feel free to move it.
About a week ago I noticed a slight miss/stumble during climb out. This occurred twice, but not on every climb out. It would only occur for a split second during the climb out, but did not occur during the cruise portion of the flight. Along with this symptom, during normal cruise I noticed a slight vibration that felt similar to a prop just slightly out of balance. You could see it in the glare shield. I downloaded the EFIS data from both occurrences and examined it looking for signs of something amiss. I knew the exact time of the anomaly, but it did not show in the data either because the sample rate was to coarse (1Hz) or it was not enough of an event to show up in the EGT, CHT, FF, FP etc.
After reading another post of a catastrophic valve sticking in an RV10, and then thinking back to another aircraft I owned with a Lycoming 360 having experienced a severe valve sticking. The more I thought about it the more I became was convinced that this too was sticking valve. Lycoming has a service bulletin addressing the inspection of the exhaust valve guides at 400 hour intervals, SB333C. I decided to perform the Lycoming Service Instruction No. 1425A which provides a suggested procedure to perform the action. Mike Bullock has a great write up with photos in this post http://www.vansairforce.com/community/showthread.php?t=128673 . I had all the tools including the ream from the last time I performed this task over 10 years ago on the 360.
I was correct in my assessment. Cylinders 3, 4, 5, and 6 all showed evidence of a very slight "interference" fit" and would not pass the Lycoming wobble test. The .4995" ream required a little coaxing to get started in the guides, cylinder 5 was the tightest. I completed the operation on all six exhaust guides in about 9 hours and flew it the next day.
With the 360, I religiously add TCP, a lead scavenger, to the fuel every time I fuel up. I put an additional 1400 more hours on the 360 without any issues, then replaced the engine at 2100 hrs with a Lycoming OH and have flown another 1200 hours without issue on the new engine. I'm going to start using the TCP with the 540.
After 2 hours over 4 flights I feel confident the issue was indeed the beginnings of the sticking valve syndrome. I will be flying a long trip on Monday and hope to report a continued clean bill of health.
Here are the stats on my engine and operation:
- Factory new D4A5
- 411 hours since installation
- Magneto ignition
- 90% of time accumulated is cross country
- All X/C flights are run LOP
- Phillips XC 20W-50
- Camguard additive
- CHT's never allowed to exceed 400 deg.,normal ops I see 310-360
One thing to add to this is that during the break in period I had a high amount of oil consumption. This continued through around 50 hours before it stabilized at a Qt. every 15 hours.
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