digital oil temp for O-200?

GeorgeC

GeorgeC

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GeorgeC
My C140A has an analog panel mounted oil temp gauge. It also has an Insight engine monitor.

I could get a thermocouple for the Insight.
I could also get an EI primary.

I don't have a feeling for the pros and cons, or the complexity of either approach.
 
GeorgeC said:
My C140A has an analog panel mounted oil temp gauge. It also has an Insight engine monitor.

I could get a thermocouple for the Insight.
I could also get an EI primary.

I don't have a feeling for the pros and cons, or the complexity of either approach.
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first, is the insight STC'ed for primary on the 140? if not, then you will still need the original gauge or a STC'ed primary gauge.
 
My recommendation would, assuming the original Oil temp appears to be functional, to just add the Thermocouple to the Insight.
As I recall the the Insight does have warning limits you can set to that it will throw up a warning if the temperature was out of spec.

This would be the most cost effective solution in my option and add the most functionality.

Brian
CFIIG/ASEL.
 
I agree that adding the thermocouple to the Insight would be easiest and provide some redundancy.

OTOH, I think the existing panel oil temp is of the bulb/capillary variety; replacing this with an EI would replace the capillary with a wire.

I am also tempted to ditch the Hobbs as well, if only to get rid of another oil line going through the firewall.

"Simplify and add lightness"
 
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@Bell206 @Dan Thomas

Related question: does the capillary that goes to the oil pressure temperature gauge need to be flushed out periodically?
 
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GeorgeC said:
@Bell206 @Dan Thomas

Related question: does the capillary that goes to the oil pressure gauge need to be flushed out periodically?
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No. Never touch that. The bulb, capillary and the gauge's Bourdon tube are filled with oil and sealed. The gauge is actually a pressure gauge calibrated in degrees instead of PSI. The bulb is in the engine's oil system, usually near the inlet after the pump, and as it heats up its oil heats and expands and creates pressure in its system and moves the gauge.

On many engines you have to remove that bulb to get the oil screen out at oil change. If you're careless you can damage the bulb or its line and crack something, and now the oil escapes and you have a dead gauge. I've also seen too many torn up bulb retaining nuts from guys using open-end wrenches on them, which eventually deform the nut and then the wrench slips and rounds off the hex, so now we see vise-grip marks. That nut cannot be replaced except at gauge overhaul, as it's trapped on the line behind the bulb. Get a proper set of flare nut wrenches for this. And hold the adapter fitting with a wrench while you loosen or tighten the bulb nut. If it moves, the copper crush gasket under it might start leaking. Now you're looking for a new gasket. Don't overtighten the bulb nut or you can distort the narrow flange on it that the nut pinches in the adapter fitting.

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Those mechanical gauges can be a pain. Modern systems use a thermistor sensor that screws into that same port and stays there. The gauge wire is disconnected from it for screen removal. A thermistor is a resistor whose resistance goes down as its temperature rises, the opposite of the usual state of affairs with electrical stuff. Temp goes up, resistance falls, more current flows, driving the gauge higher.
 
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Thanks, that reinforces my desire to replace that gauge.
 
GeorgeC said:
Thanks, that reinforces my desire to replace that gauge.
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Oops. I typed my answer this morning on my first cup of coffee. I just checked now and see that you were asking about the oil pressure gauge, not the oil temp gauge. No, oil oil pressure line doesn't need flushing out.

Gotta make stronger coffee.
 
Ugh, that was a typo. I meant oil temp.
 
Dan Thomas said:
On many engines you have to remove that bulb to get the oil screen out at oil change.
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Stop me if you've heard this one before... now I'm curious if that screen was removed when the oil filter was added, and if not, if it's ever been looked at in recent memory.
 
GeorgeC said:
Stop me if you've heard this one before... now I'm curious if that screen was removed when the oil filter was added, and if not, if it's ever been looked at in recent memory.
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It depends on the filter adapter. Some leave the screen housing as-is and run hoses to a separate filter bracket. The O-200 has a filter mount on the left aft side of the case. But most Lycoming spin-on filters go on an adapter that replaces the screen housing entirely.
 
This is an O-200, no hoses. I'll have to look at the paperwork when I get the plane back from annual.
 
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