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Oil tem gauge issue. Continental 145

Richgj3

BENEFACTOR
LI,NY
On my new to me C170B the oil temp gauge was changed during the pre buy with a gauge from AC Spruce. It’s the standard thing that has a bulb that goes into the back of the oil screen like every small continental you’ve ever seen

it reads zero then at some point in the flight it jumps up to a normal reading. Sometimes takes 30 minutes. Sometimes longer. And once on the second flight of the day after it started working on the previous flight, it continued to work. I’ve tapped on it with no result. I guess it will have to be replaced but I’m curious to know what the failure mode is. I really don’t understand the principle behind how this type gauge works.

The old gauge that was removed is definitely dead.

Thanks
Rich
 
put bulb in boiling water to verify it works/responds fast.....

or else maybe it's telling the truth?

I tested the old one that way to be sure it was really bad. My concern is, how could it be telling the truth? Oil pressure is steady in the green. All six EGT are good. Engine has about 10 plus hours on it since the gauge was changed. Let me re phrase that. I hope it’s not telling the truth. When it does come alive it goes from zero to 175 in an instant.
Good point though. I’ll test it before I take it out.

Thanks
 
There’s no oil cooler on these engines. Would there still be a thermostatic control? This engine does have the oil filter adapter.

check like i said first....

or the other answer is the temp bulb has no oil getting to it to measure temperature of..............???
 
Rich, The instrument looks something like this:
10.jpg


The temperature bulb and it's armored (or not) feed tube are connected where the picture shows "socket assembly". The entire bulb, tube and Bourdon tube are filled and sealed with a special liquid. When the liquid changes temperature, it expands or contracts. This reacts in the Bourdon tube which then straightens or curls. The end of the Bourdon tube is connected through linkages and sprockets to the instrument pointer. As the temperature rises the needle moves, as it cools the needle moves in the other direction. Simple.
Your instrument is defective as there is a mechanical interference between the Bourdon tube and the needle pointer. Once the temperature rises enough to overcome the interference location, all is good. That instrument needs to replaced or repaired.

Many instruments operate on this same principle. Altimeter, Manifold pressure, Oil pressure, Barometer, etc.
 
The mechanical gauges at ACS that I looked at were not FAA approved, not even the Rochester gauge. That pretty much guarantees made in China to be--- ahhhh----inexpensive. I think you got a bumb gauge that missed quality control and the bourdon tube or the gears stick at zero.
 
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