Ask Paul: Why is my engine oil creamy?

Q: I am doing a 100-hour inspection on a Piper Aztec with TSIO 540 Lycomings using Shell 15/50 oil with 50 hours on the oil. They are both midtime engines on this photo plane. They fly six hours a day at low power settings. The left engine oil is black like it should be after 50 hours. The right engine oil is a light creamy color. Something is not right.

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Ask Paul: What’s causing vibration?

Q: I recently installed a new three-blade propeller in my Comanche 250 with an O-540 engine. After the first flight I noticed a vibration when I decrease the rpm to 2400 or below, so I had the prop dynamically balanced. This did not change anything. The engine still vibrated.

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Ask Paul: What’s the TBO on my engine?

Q: I have obtained a 1978 Bellanca 7GCBC with a Lycoming 0-320-A2B engine manufactured in 1977. I am attempting to learn more about this engine, including why the log book contains an entry at the 1,200 hour mark showing the engine as being “on condition” but I have been unable to determine why.

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Ask Paul: Fly more, get longer TBO?

Q: I bought my first plane, a 1981 Cessna T182RG, in May 2012. I have been flying this plane frequently and have put over 300 hours on it in the last calendar year. I can tell you that in 2005 it received a factory remanufactured engine from Lycoming and at the 1,000 hour mark got a complete top end overhaul. Now Lycoming shows the TBO at 2,000 hours, but I have found documentation from Lycoming that put the TBO at 2,200 hours providing you are running at 40 hours a month. For me that translates to the more you run the engine the more hours you can squeeze out of it.

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Ask Paul: What’s causing intermittent roughness?

Q: I am an European-based A&P with a customer who is experiencing intermittent roughness and loss of rpm (200) typically close to the top of climb on a long climb out. The roughness goes away once it is throttled back, and it does not occur all the time. The snag can’t be produced on the ground. The aircraft is just off annual check and had the 1,000 hours mag inspection carried out, apart from various other visual inspections, plus the routine other items.

I’ve thought about the possibility of a sticky valve, an issue in the carb venturi or some issue with the mags, but thought if it were any of these that the issue would be there all the time?

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What’s causing Mooney’s rough-running engine?

Q: I bought an older Mooney with a Lycoming IO-360 with Bendix fuel servo. The engine starts to run rough once the last 1/2 inch of throttle is given. An induction leak cannot be located. Would a faulty sniffle valve be to blame? Any other possibilities?

JAMIE RICHARDS

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Does flight school’s 172 need new rings?

This question was initially sent to our fuels and oil expert Ben Visser, who passed it on to our engines expert Paul McBride for further comment.

Q: Our flight school has a Cessna 172N with an O-320 H2AD. The engine was rebuilt 120 hours ago after cam/lifter failure. The engine uses one half quart of Aeroshell 100 Plus every hour! Oil analysis iron ppm is very low. Compression was 75-78 at 100 hour. Do you think that the rings did not seat? Do I pull the cylinders for new rings and hone?

Denney Marsh, Hemet-Ryan Flight School 

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Ask Paul: Upgrading to a wide deck engine

Q: I read your article from the Oct .7, 2009, issue of General Aviation News on Wide Deck vs. Narrow Deck Lycomings with great interest. I am trying to figure out one detail that I think your article answers, but I just want to make sure.

I have a 1960 PA-22 Tripacer that originally came with a 150-hp O-320-A2B ND engine. It is ready for a major overhaul, and my IA recommends that I upgrade to a WD O-320-B2B engine.

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Ask Paul: The Cherokee Rattle

Q: I just bought a 1974 300-hp Cherokee Six. It has about 1,200 hours to run, has great oil pressure, good compressions, hardly uses oil, no metal in the filter, but during the run-up at 2,000 rpm, the engine makes quite a deep knock.

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What are the best options for overhaul?

Q: My question seeks your advice about an overhaul on our Lycoming O-320-H2AD. As background, we have a 1980 C172N that’s been owned since new. It’s always been hangared, never been a flying club or training airplane, is not used for commercial purposes, and has 2,420 TTAFE tach time.

The engine is the original H2AD and it has not been topped. [Read more...]