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  #1  
Old 07-05-2018, 12:32 PM
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Join Date: Jun 2010
Location: Miami Beach, Florida
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Water temp. sensor or temp. gauge, which one is it?

On my 76 280C, the temp needle fluctuates, from the midway mark down to about an eighth of an inch below that.
Sometimes even more. It seems that in the freeway it goes a little above the midway mark. I thought that on the freeway it should drive cooler.
Is my water temp sensor taking a dump or is it my gauge?
The car has new thermostat and new water pump and new coolant. Clutch fan was replaced about two months ago.

Thanks in advance
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  #2  
Old 07-05-2018, 02:12 PM
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It's probably OK, is this movement new? You might be seeing the thermostat cycle at low / mid speed and the higher speed, higher load is keeping it open.

I have seen low coolant move the gauge around but it is usually more of a dramatic swing.

You could hang a ohm meter on the ( disconnected ) coolant sender and watch for movement.

A trick for determining thermostat opening point.

With an overnight cooling of the engine, start engine and let idle. Watch the temp climb, at some point it will drop a bit due to cold water in the radiator entering the engine, this is the thermostat opening temp. The temp will then climb back up, stat open again but the drop will be less than the first go around. At some point there will be a barely discernible fluctuation as the stat cycles.

This works for most cars however, radiators with a bleed line or heater hose returning to the return side tank ( 80's GM ) the drop in temp during stat opening will be less apparent.
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  #3  
Old 07-05-2018, 05:29 PM
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Yes, this is new. There was always a fluctuation but now it seems that it's more aggressive. My needle never went up to the half way point and it never passed it.
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DRIVE RIGHT PASS LEFT
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  #4  
Old 07-06-2018, 09:39 AM
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Location: Central Ky
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mid point is fine, and under load it will get hotter even at highway speeds. I suspect you are now seeing normal operation after the new thermostat installed
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  #5  
Old 07-06-2018, 03:20 PM
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My car does the same thing and I did everything you did as well as re-core the radiator. And on the highway, mine drives around 200F-212F and sometimes just slightly higher than the 212F mark. I want to get my timing set and see if that'll help.
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