TrueCourse
Line Up and Wait
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TrueCourse
Are the feathers tarred?Which weighs more? A pound of feathers, or a pound of lead?
Are the feathers tarred?Which weighs more? A pound of feathers, or a pound of lead?
I don't have any sort of engine monitoring so I have one CHT gauge and it doesn't seem overly highHow are your CHT's? Any change there? That might be an indication of a baffling, timing, or mixture change.
Any indication that you're getting more blowby through the rings?
This is something that would be caught on a compression check right?I had this issue and it turned out to be a failing cylinder that was blowing a significant amount of combustion exhaust into the crankcase. Eventually the cylinder seals completely failed and my oil temp gauge hit redline, forcing an emergency landing. I had noticed that the oil was getting dark quite quickly, but attributed it to just being an old O-200. Replaced the failed cylinder and everything went back to normal.
YesThis is something that would be caught on a compression check right?
Get a cheap IR thermometer and measure all four cylinders after landing. See if one is significantly hotter.I don't have any sort of engine monitoring so I have one CHT gauge and it doesn't seem overly high
Curious - what does it indicate if one is hotter? Also, what about the other two cylinders? ;-)Get a cheap IR thermometer and measure all four cylinders after landing. See if one is significantly hotter.
Okay I will head to the airport and do this nowGet a cheap IR thermometer and measure all four cylinders after landing. See if one is significantly hotter.
Advanced timing can heat the entire engine, including the oil. Unfortunately, Bryan has an analog oil temp gauge, so it is hard to objectively determine whether he's seeing a "normal" slightly higher oil temp due to higher OAT or if something has changed. CHT's might give an indication.I thought that problem was oil temp…
I thought that problem was oil temp…
Yes, but don't rely on your most recent annual to eliminate that possibility. My aircraft passed compression checks perfectly and then three months later the seals blew and pegged the oil temp gauge. It sounds like this reading change occurred relatively quickly, rather than being a slow onset. This suggests a quick failure (or incipient failure) of something to me, rather than a slow clogging or degradation. In my case, I noticed higher than normal temps for about a month which I attributed to the California Central Valley being an oven-baked hellscape in the summer before the complete failure occurred. In retrospect, the high oil temps were my indication that a cylinder was about to let go.This is something that would be caught on a compression check right?
Due to excessive flying, I am changing my oil a lot. I haven't noticed any alarming chunks of metal in the filter, Just the typical glitter from time to time.In order of accessibility to the normal human (not an A&P) depending on tool availability:
-Cut the filter to look for excess metal (friction derived heat).
-Borescope for anything obvious (cylinder wall issues).
-Leakdown test
-Mag timing
Not sure if cylinder leanness caused by fueling (clogged injector or induction air leak) would cause high oil temps, unless maybe across the board on all cylinders?
Would that result in a different temperature reading between engine running/ charging vs engine stopped?A poor engine ground to the airframe can do it.
The alternator causes electron flow from the bus, through the alternator to the engine ground (or to airframe ground via a dedicated alternator ground cable), thence to the negative battery post, through the battery (which charges it, since this flow is reverse to normal battery discharge flow), and out of the positive battery post to the bus.
Now, the oil temperature sensor is a brass fitting that screws into the oil filter housing. It has one terminal, which leads to the oil temperature gauge. The other side of the oil temp gauge goes to the bus. The bus power pulls electrons through the gauge, which gets them from the engine crankcase vie the sensor, which has a resistor in it that lowers its resistance when it gets hot.
If the alternator is not well-grounded to the airframe, those electrons from it like to find other paths to the airframe, and one of those paths is through the oil temp sensor and to the gauge. This increases the electron flow through the gauge, spiking it.
Yup. I mentioned that on another oil-temp thread. In post #25 of this thread I suggested this:Would that result in a different temperature reading between engine running/ charging vs engine stopped?
I would think that once the engine is warmed up, one could compare the indicated temperature just before and after shut down. That should be a rapid change compared to the time it takes for things to actually cool down.
Another way of proving it is to load up the alternator in flight and see what the temp needle does. More current will mean more gauge error if the grounding is bad.