Temperature gauge
Thread Starter
Burning Brakes
Joined: Feb 2022
Posts: 985
Likes: 183
From: South Carolina
Temperature gauge
I just recently finished the interior and trying to get everything button up,all my gauges seem to work,except water temperature,which when I replaced the heads,I replaced the censor,but the size in the head was bigger,so had to add a coupling or maybe a reducer,to fit the censor,so is it possible that it’s just not reading it,or maybe the new one is bad,I have my old one that I took out,and can I just hook the wire up to the old one,not in the head,take a lighter and heat the end up,to see if the needle will move with the key switched on,or does it need to be grounded to the head,I’m pretty certain the old one was good when I changed heads. Thanks I hope I’m making sense.but,I guess my main thing is,does that end of the sensor,need to be all the way in the head,because mine isn’t.
Race Director
Joined: Nov 2006
Posts: 13,151
Likes: 7,765
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
Just take the wire that goes to the sensor. Ground it to the head. What happens at the gauge? Swings all the way hot? Good wiring, bad sensor. Nothing? Bad wiring or guage.
have someone looking at the gauge for you. Don't want to ground it for to long.
have someone looking at the gauge for you. Don't want to ground it for to long.
Race Director
Joined: Nov 2006
Posts: 13,151
Likes: 7,765
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
The other question. It's not ideal to not have the sensor in the head. However just about any replacement sensor won't read correctly anyway. Your original sensor even if it's not completely in the head will still be touching hot coolant. Should still work.
Drifting
Joined: Jun 2025
Posts: 1,635
Likes: 575
You've already heard how replacement electrical senders/sensors are either not accurate or are wrong impedance to match OE C3 gages.
I suggest to you, that by using a reducer fitting to graft your larger sender to the new head's smaller hole, you may've created another aggravation.
It seems the sender should be constantly, continuously inserted into a moving liquid fluid stream. It also seems your sender may now be inserted into a somewhat stagnant environment; perhaps where air/steam pockets are as well.
No doubt: inaccuracy and wrong impedance are two different factors; and can exist either singularly OR, in this matter, in tandem as well. Cannot KNOW from afar.
If it were mine: I would first separately test and Verify the sender's Accuracy and Repeatability and that, in concert w/ OE gage, does produce a reasonably true representation of engine temps. Once that's resolved, and sender's proven accurate, I'd either enlarge & re-thread hole in head OR have that good sender turned down in a lathe and re-threaded to mate with hole in head. I'd re-position an accurate sender into a continuously moving stream of liquid coolant; directly into side of head per OE.
I suggest to you, that by using a reducer fitting to graft your larger sender to the new head's smaller hole, you may've created another aggravation.
It seems the sender should be constantly, continuously inserted into a moving liquid fluid stream. It also seems your sender may now be inserted into a somewhat stagnant environment; perhaps where air/steam pockets are as well.
No doubt: inaccuracy and wrong impedance are two different factors; and can exist either singularly OR, in this matter, in tandem as well. Cannot KNOW from afar.
If it were mine: I would first separately test and Verify the sender's Accuracy and Repeatability and that, in concert w/ OE gage, does produce a reasonably true representation of engine temps. Once that's resolved, and sender's proven accurate, I'd either enlarge & re-thread hole in head OR have that good sender turned down in a lathe and re-threaded to mate with hole in head. I'd re-position an accurate sender into a continuously moving stream of liquid coolant; directly into side of head per OE.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Drifting
Joined: Jun 2025
Posts: 1,635
Likes: 575
And found that not so.
In practice, I've found the tapered pipe thread Teflon tape or sealant cannot & does not prevent the tapered threads from both cutting into one another and cutting through the Teflon / sealant.
I've also found that many OE GM and OE GM replacement senders deliver with a thread sealer on them; right out of the box. Typically a sort of brick-red color.
With that said, I cannot dismiss the possibility that Teflon tape may've interrupted ground path.
Last edited by Rebelyell; Mar 12, 2026 at 07:19 PM.
Race Director
Joined: Nov 2006
Posts: 13,151
Likes: 7,765
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
Highly unlikely that Teflon tape would interrupt the ground.
That's a myth.
That's a myth.
Advanced
Joined: Aug 2025
Posts: 61
Likes: 36
I spent weeks dealing with that last summer. Probably have half dozen sensors laying around. Just couldn't find one to fit properly and that works with original gauge. Thinking for peace of mind I'll install another temp sender on the passenger side head to a gauge that I temporarily install where I can see it and compare readings for months. Then I'll just live it knowing what it really means. But I would sure like a real fix and be able to keep the original gauges like they are.
Watching.
Watching.
Thread Starter
Burning Brakes
Joined: Feb 2022
Posts: 985
Likes: 183
From: South Carolina
Yep,I have about 4 sensors,none worked,so I just went to the parts place and bought one off the shelf,and even tested it in a pot of boiling water,and worked like a charm,so, put it in. So I had already drained the radiator,which I have to ask,the drain petcock at the bottom,I have a plastic plug with just a little nub on it which is hard to screw,and unscrew it,does everyone put a different or even longer plug in it,it’s hard to get pliers on it,I finally removed the plug yesterday,and it had a notch opening in it,never seen that type plug before,so guessing this type plug isn’t meant to actually be removed or loosening a lot to drain radiator,it also has a washer on it that is kind of loose,what made me remove the plug,I started putting anti freeze and noticed it dripping from plug,and it was tight,but thinking the washer wasn’t centered,or is stretched or something making not seal completely,wonder if a little sealant around it after I tightened up. Thanks
Race Director
Joined: Nov 2006
Posts: 13,151
Likes: 7,765
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
I removed the drain plug from my radiator and installed a sacrificial anode in its place to protect the aluminium radiator. No leaks. And I can drain by simply removing it.