182 oil temp workings

flyingcheesehead

flyingcheesehead

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Quick question:

On a Cessna 182N with the O-470-R engine, how does the oil temperature gauge work, exactly? Is there an oil line running from the engine compartment to the gauge and the sensor is in the gauge, or is there a sensor in the engine compartment with a wire running to the gauge?

Second - I'm assuming the answer to the first question is "a" (oil line runs through firewall to the gauge), let's just say you were having a new starter placed on the engine. Is the oil line for the gauge running up the firewall behind where the starter sits? Could you inadvertently damage the oil line while installing a new starter?

Thanks,

Kent
 
I don't think an oil temp gage would work that way. An oil pressure gage, yes. So, if you damaged an oil line then I think that would be the line running to your oil pressure gage not oil temp.
 
I don't think either work that way. Both the temp and the pressure use sensors at the engine. The oil pressure would use a transducer at the enginem, the oil temp would use a temp probe and convert these would then convert measurement into a voltage, that is then displayed by the gauges, IOW no oil lines running to your instrument panel.
 
smigaldi said:
I don't think either work that way. Both the temp and the pressure use sensors at the engine. The oil pressure would use a transducer at the enginem, the oil temp would use a temp probe and convert these would then convert measurement into a voltage, that is then displayed by the gauges, IOW no oil lines running to your instrument panel.
Click to expand...

A- So no Bourdon tubes in the guage (this would lead oil to the instrument panel)? Some books seem to indicate otherwise- maybe this is an old way of doing things...

B- Or is the Bourdon tube attached to a strain guage (no oil going to the instrument panel)?

C- No bourdon tube at all (uses diaphram and strain measurement on the diaphram)?

D- None of the above?

I'm merely asking to bring myself to modern times. Glass cockpits would use options B or C (most likely C).
 
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Cap'n Jack said:
A- So no Bourdon tubes in the guage (this would lead oil to the instrument panel)? Some books seem to indicate otherwise- maybe this is an old way of doing things...

B- Or is the Bourdon tube attached to a strain guage (no oil going to the instrument panel)?

C- No bourdon tube at all (uses diaphram and strain measurement on the diaphram)?

D- None of the above?

I'm merely asking to bring myself to modern times. Glass cockpits would use options B or C (most likely C).
Click to expand...

I'm not sure when Cessna changed from the Bourdon tube gauges to the electric, but it was around 1973 or so, I think. Your 182N is what year? If it came out with the Bourdon tube gauge, it might still have it or it might have been changed, since Cessna no longer provides that system; they supply a kit to change to the electric gauge.

You'll need to find the oil screen housing and see what's screwed into it. If it has a wire, it's electric. If it has a really tiny copper tube with a spiral wrap of wire around it, it's the fragile Bourdon tube type that's liable to get busted if it's pushed around much. If it gets broken, you pretty much have to buy the kit from Cessna because of their gauge cluster, and that kit ain't cheap. There are folks who repair broken Bourdon gauges but it can cost as much as the kit, I think.
Here's a picture of a Bourdon tube temp gauge (center gauge); note the spiral-wrapped tubing to the pickup bulb. Cessna's gauge has a tube like that but the gauge is small and rectangular and has no housing.
IMG_0134-1.jpg


See this page and scroll down to the last two pictures:

http://150cessna.tripod.com/oilflow.html

Dan
 
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smigaldi said:
I don't think either work that way. Both the temp and the pressure use sensors at the engine. The oil pressure would use a transducer at the enginem, the oil temp would use a temp probe and convert these would then convert measurement into a voltage, that is then displayed by the gauges, IOW no oil lines running to your instrument panel.
Click to expand...

Lots of airplanes use mechanical oil pressure gauges (oil line) and temp bulb oil temp gauges with oil lines running to the instrument panel.

Dan Thomas said:
I'm not sure when Cessna changed from the Bourdon tube gauges to the electric, but it was around 1973 or so, I think. Your 182N is what year? If it came out with the Bourdon tube gauge, it might still have it or it might have been changed, since Cessna no longer provides that system; they supply a kit to change to the electric gauge.
Click to expand...

My 337 Skymaster is a 1974 and it has the type gauges with the oil lines going to the gauge. When I did the avionics refit last year I replaced the oil lines behind the instrument panel.
 
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Dan Thomas said:
I'm not sure when Cessna changed from the Bourdon tube gauges to the electric, but it was around 1973 or so, I think. Your 182N is what year? If it came out with the Bourdon tube gauge, it might still have it or it might have been changed, since Cessna no longer provides that system; they supply a kit to change to the electric gauge.

You'll need to find the oil screen housing and see what's screwed into it. If it has a wire, it's electric. If it has a really tiny copper tube with a spiral wrap of wire around it, it's the fragile Bourdon tube type that's liable to get busted if it's pushed around much. If it gets broken, you pretty much have to buy the kit from Cessna because of their gauge cluster, and that kit ain't cheap. There are folks who repair broken Bourdon gauges but it can cost as much as the kit, I think.
Here's a picture of a Bourdon tube temp gauge (center gauge); note the spiral-wrapped tubing to the pickup bulb. Cessna's gauge has a tube like that but the gauge is small and rectangular and has no housing.
[snip]
Click to expand...

Nice explanation. So the oil temperature sensor doesn't actually send engine oil to the display. All we see is the thermal expansion of the fluid (probably mineral oil of some sort) in the bulb.
 
Dan Thomas said:
I'm not sure when Cessna changed from the Bourdon tube gauges to the electric, but it was around 1973 or so, I think. Your 182N is what year?
Click to expand...

1971.

If it came out with the Bourdon tube gauge, it might still have it or it might have been changed, since Cessna no longer provides that system; they supply a kit to change to the electric gauge.
Click to expand...

Still had the old style. I was looking around and learning as they were hanging the engine, and I specifically asked about it. It was an oil tube. Next thing ya know, we're getting a call that "it broke." :nono:

If it gets broken, you pretty much have to buy the kit from Cessna because of their gauge cluster, and that kit ain't cheap.
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$1,367.92 not cheap. :mad:

Great info Dan, thanks a heap. If nothing else, I guess it'll be harder for them to break next time. :sosp:
 
The lines behind the instrument panel can get interesting. As they're metal, they will fatigue with vibration and can eventually break with minimal warning. This happened on my friend's Travel Air in Anderson, SC a month or so back when we were down for an animal rescue flight. Bending them will cause fatigue, too. So, if you are doing some maintenance that unintentionally bends the lines, you could inadvertently break them.

The good part about this (I can tell you from personal experience when I had my XJ-S with a 12-quart sump) is that it will take the better part of 30-40 minutes before you dump all the oil from your sump into the cabin. You'll probably notice it soon and decide you need to land if that happens. Still probably not a bad idea to replace "if you're there" and you know the lines are really old.
 
Ted DuPuis said:
The good part about this (I can tell you from personal experience when I had my XJ-S with a 12-quart sump) is that it will take the better part of 30-40 minutes before you dump all the oil from your sump into the cabin. You'll probably notice it soon and decide you need to land if that happens. Still probably not a bad idea to replace "if you're there" and you know the lines are really old.
Click to expand...

That's assuming the flow restrictor is in place where the oil pressure line attaches to the engine. Sometimes these get left out and in that case you can lose the oil a lot faster.

I have had an oil pressure gauge line break but the failure occurred between the engine and firewall, most likely due to the fact that this portion of the tubing sees a lot more movement during normal use.

And just to clear one thing up, only the oil pressure line contains oil from the engine. The oil temperature line on a Bourdon tube type gauge might contain some sort of oil (usually alcohol AFaIK) but it's sealed from the engine and breaking that line only results in the loss of the temp reading, not the engine's oil supply.
 
Waidaminit! They call you, saying "It's broke" (implying *they* broke it), then charge you? Methinks you "otter" go down to the FBO and gently, kindly correct their error. Bet it wasn't broke before you handed the plane over to them to r/r the starter...
 
jshawley said:
Waidaminit! They call you, saying "It's broke" (implying *they* broke it), then charge you? Methinks you "otter" go down to the FBO and gently, kindly correct their error. Bet it wasn't broke before you handed the plane over to them to r/r the starter...
Click to expand...

We had a meeting with them - It wasn't just the starter, it was the whole engine. The final bill ended up close to 50% higher than the original quote. VP we talked to was seemingly helpful and understanding, he's going to do some more investigation and get back to us with a number for what they're going to take off the bill. I have a number that I believe is reasonable. Hopefully they'll beat that number...
 
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