switch/sensor identification- side of engine - JeepForum.com
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post #1 of 8 Old 09-05-2019, 09:54 AM Thread Starter
mc190
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switch/sensor identification- side of engine

Cleaning up the engine on a 258 I6.


Anyone know what this sensor/switch is located on the engine block. It is the one on the left. The other one is the CTO/ Ported Vacuum Switch.


when removing the headers and exhaust, the wiring from that switch separated. Just have no idea what it is.


Thinking about removing the ported vacuum switch as well. Nothing is hooked up to in anyway.

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post #2 of 8 Old 09-05-2019, 11:10 AM
John Strenk
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Looks like someone put a temperature sending unit in there.

that looks like a bourdon tube attached to it.


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post #3 of 8 Old 09-09-2019, 06:31 AM Thread Starter
mc190
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a better picture of the unknown switch.
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post #4 of 8 Old 09-09-2019, 06:38 AM
Hoover7
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I agree with John, looks like an old temperature sending unit. That's where I have mine mounted on the 258.

Hoov

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post #5 of 8 Old 09-09-2019, 07:08 AM Thread Starter
mc190
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Been too darn hot to work on the Jeep in the afternoons, so have not been able to trace back that wire/tubing to see where it goes.

Assuming its a temp sending unit, were can I get a replacement bourdon tube that John mentions.
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post #6 of 8 Old 09-09-2019, 10:16 AM
John Strenk
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Quote:
Originally Posted by mc190 View Post
Been too darn hot to work on the Jeep in the afternoons, so have not been able to trace back that wire/tubing to see where it goes.

Assuming its a temp sending unit, were can I get a replacement bourdon tube that John mentions.
You can't. They are a sealed unit from the sensor to the gauge.

You have to replace the whole gauge.

Quote:
The Bourdon Tube
A Bourdon Tube is a thin metal — usually brass or copper — tube that is filled with an easily vaporized fluid, typically alcohol. It is sealed at both ends. At the gauge end it is formed into a circle or spiral with its end attached to the indicating needle by some form of linkage. The other end is fitted to a water-tight connector that is in direct contact with the coolant in the engine.

As the coolant warms up the alcohol in the Bourdon tube expands. The expansion transfers its force to the coiled end of the tube inside the gauge. As the coil or spiral unwinds it pulls the linkage on the needle, which in turn shows a temperature reading on the gauge face. The gauges are calibrated during the manufacturing stage and are not adjustable afterward.

Since the Bourdon Tube design is purely mechanical the gauge will continue to read some temperature level even after the engine is shut off. As the engine cools the gauge's needle will return to its rest position.

Bourdon Tube gauges aren't used anymore because of cost and convenience factors. The tubes are delicate and must be carefully routed from the dash to the appropriate fitting on the engine. The gauges themselves are far more expensive than electric or electronic gauges and if the tube is kinked or split the entire gauge assembly must be replaced.
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post #7 of 8 Old 09-09-2019, 03:51 PM Thread Starter
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Thanks for the explanation on The Bourdon Tube.

Looks like converting it over to an electric style.
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post #8 of 8 Old 09-10-2019, 08:16 AM
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Quote:
Originally Posted by Hoover7 View Post
I agree with John, looks like an old temperature sending unit. That's where I have mine mounted on the 258.

Hoov
I did that too.

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