11/24/2023 0 Comments Oily spark plugIf you own a pressurized Cessna Skymaster, Piper Seneca II or III, Piper Turbo Arrow, or maybe a Moonie 231, you’re likely driving around with a Continental TSIO 360 engine and these engines have to be watched for very small oil leaks on the back side of the cylinder’s rocker box. On the surface, a weep would seem to be less potential trouble than either a drip or a leak. Oil leaks are another source of consternation, but all leaks are not created equal – there are weeps, drips, and leaks. Tell him your theory about the migrating rings and if you get agreement, wait it out for five hours before taking any action. Instead, have your A&P take a look just to err on the side of safety. The point here is this: If your engine has been behaving itself and all the sudden the oil usage goes way up, don’t jump to the conclusion you have to immediately replace a cylinder. Of course, this can happen over time with worn-out cylinders as well, but we’re talking about “sudden onset” oil usage. Normally the engine speaks to you by generously coating the underside of your airplane with oil. (The crankcase gets pressurized when this happens and the oil goes out the breather). It’s common for the rings to rotate around a piston and occasionally they’ll line up in such a way that the oil can find an easy path to the outside. In that case, wait five hours and check it again. What about an engine that suddenly develops oil loss problems? Once I have either or both of these numbers present, I’m done with the cylinder(s) in questions.īut that’s a constant situation. The question then becomes how much oil loss and/or loss of compression are you willing to live with? For me, a quart an hour and compression below 60/100 is all I’m going to put up with. You’ve just got an engine that’s happiest running half to one quart low and there’s no point in fighting it because it’ll win the argument every time.īut if you have a constant oil loss and the compression on one or more cylinders is in the 65/80 range or less, you probably do have a cylinder that is going to need to be reworked. The missing oil has disappeared but it doesn’t matter. In most engines there will be a loss of oil in the first few hours after an oil change, but it will stabilize somewhere around a half quart and a full quart below the full mark. If compression is good on all the cylinders but oil is disappearing, the first thing to determine is if there’s a point – somewhat lower than a full crankcase – where the oil loss stops. What’s an engine trying to tell us when it weeps oil, burns oil, or coats spark plugs with oil? Oil Usage Finally, removing a spark plug and finding the business end covered with thick, black oil generally renders us apoplectic and unfit to be around for days. That said, most of us get nervous anytime we use more than a quart every 3-4 hours and all of us get very anxious when a previously “tight” engine starts leaking oil. There are oil usage specs out there for each and every piston engine that pull aviators around the sky but the rule of thumb is anything less than one quart per hour doesn’t require immediate action. Engines tend to be gabby, but they sometimes speak very softly. Today’s task is to learn how to listen and watch for the signs that your aircraft engine throws your way. What Your Oil, Spark Plugs, and EGT Gauge Are Trying to Tell You
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