Electrical Another temperature gauge post

LATT5133

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Ok guys, two weeks ago I pulled my plugs to check them. Upon completion I hooked up the battery then reset my stereo settings etc. The next morning I cranked her up and noticed my voltmeter down toward the bottom quarter of the gauge, so I traded cars to follow up in the afternoon. I have an SVE 3G set up with 4G power wire so I figured maybe I hit something messing with my plugs. Upon further investigation I find my negative battery cable had split (wire and connector separated). Replaced that. Did an entire system test with DMM which all under hood components tested good. Additional reading I see where the voltmeter and resistor are an integral part of the charging circuit. I pull the instrument cluster out and realize the copper wire back plate is damaged around the voltmeter / resistor connection. Test with DMM and no continuity. I solder the link and test again, now I have continuity. While in there I see I am missing the low coolant light and light socket. I replace that and put everything back together. Works like a charm. Next morning driving to work and getting on the on 75 on ramp ramp I noticed my temp cross the center line on the factory gauge. Never comes above center, since replacing the factory radiator because of a leak. I have an SVE 3 core. Coolant overflow works as designed and this drive usually nets about an inch to an inch and a half of additional coolant from expansion and returns to cold level when cool. In the days since I am noticing the needle drifting above center it continues to show elevation up to the bottom of the N in normal on the factory gauge. Low coolant light is on continuous too, not low though. I have burped with her jacked up and have a Mr Gasket 180 T-stat. I have been scouring this site looking for test options. I have since tested my factory gauge/wiring by un plugging the water temp gauge sending unit wire and grounding with key on she tests good, swings to top of gauge, remove wire from ground and it returns. I have replaced the sending unit, still the same, although it takes a bit longer (few miles) to swing passed the center position on the gauge. I am now at a loss. I would like to figure out what is giving me fits rather than replacing gauges as she is pretty much stock and does not need a host of autometer gauges. Someone help, ready to follow instructions!

Jason
 
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LATT5133

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UPDATE #1 Bought an Infrared Thermometer, did not realize they were as cheap as a sunpro water temp gauge. So the factory gauge continues to drift northward, now on top of the N. IR Temp at T-Stat housing reads a consistent 210-212. Top passenger side of radiator is 210 and top drivers side is 174-176. I am guessing I have some work to do in figuring out grounding issues? Thoughts

Jason
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General karthief

wonder how much it would cost to ship you a pair
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I realize you are seeing a change in the temp gauge readings, when dealing with stock gauges connections can change readings, even a charging issue can make the gauge move around, put a aftermarket mechanical gauge in it to get real readings, even if just temporary, then you will know what the temp is and how much it increases and when.
JMO
 
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7991LXnSHO

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Out of diagnostic curiosity, do the other gauges also move up at the same time or soon after?
 

LATT5133

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Out of diagnostic curiosity, do the other gauges also move up at the same time or soon after?
To date, the only gauge that seems to move even the slightest would be the volt meter (same side) movement is roughly 1/16" lower than it normally reads since the start of the water temp gauge issue, if that helps?
 

LATT5133

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I realize you are seeing a change in the temp gauge readings, when dealing with stock gauges connections can change readings, even a charging issue can make the gauge move around, put a aftermarket mechanical gauge in it to get real readings, even if just temporary, then you will know what the temp is and how much it increases and when.
JMO
True, and I may have to go that route if I cant fix this adequitely.
 

LATT5133

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I suggested the mechanical gauge to compare to the stock gauge, when the stock gauge moves you can see and compare the actual tempt.
Yes, I am going to do this to get an accurate read on what is going on. I am flushing the system first, I just found some black "sludge" like substance on the underside of the radiator cap? This is new... May have to crack her open?
 
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LATT5133

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UPDATE # 2
So when burping your 5.0 I am assuming that violent bursts of hot coolant from the radiator is a bad thing, like maybe a head gasket, or maybe ? I just burped her when I recently replaced the radiator and it was just bubbles. This was blowing about 12 oz a pop. I had to throw a shop towel over it to diffuse the blow so as not to get 195 deg water on my other cars. Let me know if there is a law of percentages between head or intake. One will not be bad but if I am taking it down to the heads then a Trick Flow top end is going back in...
 

LATT5133

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UPDATE # 3 (Final) Ok, so I negated to check one item on the standard cooling system troubleshooting by the numbers. Thermostat, I had recently replaced my motorcraft 192 T-Stat with a Mr. Gasket 180. Well, I should have checked it first as it failed. Took it out Friday and boiled it and my motorcraft side by side. At 190+ my Motorcraft opened as designed. Mr Gasket never cracked up to 210 or so... Put the old one back in and problem solved. Mechanical gauge has her running at 195-200. Put the original sender back in and temp gauge hovers just below half way. Always trust a mechanical (Thanks General Karthief) and never overlook a new part just because it is new! Lesson learned, fortunately I did not overheat and blow a head gasket!
 

7991LXnSHO

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The FlowKooler Robert Shaw thermostats are my favorite style and brand. This one is the wrong temp temp range, but it is a great picture.
Glad you found out the defective part before something was hurt. If you are not going to run a premium brand (Robertshaw), it’s best to stick with Stant. The name Mr. Gasket has been bought out and is repackaging budget price parts, and you found out what can happen with that.
 

7991LXnSHO

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I test every thermostat on the stove before I install, you would be surprised how far off a new one can be.
Oh, don't tell 'the girl' about the stove thing.
I have a garage sale or Goodwill pan for stuff like this, and clean up after, so even my nasty ex did not complain. My good wife lets me do what is needed without flack. Her dad used to bring new calves into the mud/laundry room on the worst winter days, so making thermostat soup is pretty minor.
 
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LATT5133

Member
May 8, 2020
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Tampa, Florida
The FlowKooler Robert Shaw thermostats are my favorite style and brand. This one is the wrong temp temp range, but it is a great picture.
Glad you found out the defective part before something was hurt. If you are not going to run a premium brand (Robertshaw), it’s best to stick with Stant. The name Mr. Gasket has been bought out and is repackaging budget price parts, and you found out what can happen with that.
I will have to remember the Robert Shaw brand! Thanks!!
 
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