Temperature Gauge Increments

[DuWayne Ladner]

Can someone on here call out the increments on the temperature gauge. Is in console on the floor. Is the 1st mark 180 and so on after that. Newly restiored L78 engine. Live in the Deep South and it is hot here today heat index about 104. Couple days ago run it about 85 miles round trip to visit a new Camaro buddy with a numbers match COPO. Car ran consistently between 1st mark and 2nd mark on temp gauge. Puzzling though is it is losing fluids and can’t find it, On return trip after putting more 50/50 fluid in it, ran straight on the second mark, and needle flicked over the 2nd mark a few times before settling back on the 2nd mark. New 4-core radiator, 7 blade flex fan. I’m stumped on problem and fix. Guess I should have put this on garage talk, but I know got to be a restorer on here that May have had this problem before and can shed a little info. Thanks in advance.

[x66 714]

Your car would've had a 7 blade clutch fan. I've seen the clutch on e-bay for 800.00 to 1500.00 NOS. It should have a fan shroud. The 4 row radiator, is it a high fin count? Lots of the 4 row radiators have a low fin count & can be bought cheap. Do you have a factory guage & a factory sender? You should get a infrared gun & see if it is actually hot or just reading hot. I have a 402 car bored .010 over that has all the correct parts & it will run to the 1st mark unless I use the a/c, then it goes up but usually to the middle. It's way over 100 degrees here in Tucson....Joe

[boomer632]

Make sure your not overfilling and dumping out overflow. My L78 has the curved neck radiator and if you look on pass side about 3 inches down from top of rad is is marked with the fill level. I filled mine up past that mark after changing a hose and it puked out of overflow until it got back down to that mark.

[169INDY]

I have found this helpful when troubleshooting Temp Gage indications.

Sender Checks:
You can use a Volt-Ohm Meter and a temp gun to monitor your senders variable resistance output and chart it and compare to the various manufactures.
You disconnect the Green wire and just take a continual OHM (Resistance) readings as the car warms up.
Red lead to Sender pin Black lead to engine ground, set meter to Ohms your range will be 0-600-ish.

Gage Checks:
Remove Meter and reconnect Green wire and read gage needle reading and quickly note it, since the gage is not labeled in numerical degrees, you have to chart these and understand the relationship.

Now a Wild A$$ Guess would be; assuming a linear variable resistance; very roughly. I may be way off base , but study the Charting Temperature "Curves supplied by the link.

Cold = 70 degrees
1/4 Scale = 105
1/2 Scale = 141
3/4 Scale = 176
Hot = 212


Link

https://www.metroli.org/pdf/Temperature%20Sender%20Resistance%20Chart.pdf

[169INDY]

LoL

I just added a 1/2 Gal to my 1968 L78 Today, Still doing reliability runs and tuning the Vac Advance canister profile to obtain a stable idle with my Howards cam. Wonder ALSO where the water went or just a lot of "Burping to do when commissioning a NEW BBC

[Stingr69]

a radiator cap designed for a coolant recovery system used on a non-recovery system maybe?   Just spit balling here.  Check your cap.

[Kelley W King]

I temporarily attached a water bottle to the over flow hose to check to see if I was loosing water going down the road. My GTO had so much air trapped I use water wetter in it to get it to cool down. I also use the infared to check all my factory guage cars. The Harbor Freight 20 buck unit works fine.

[DuWayne Ladner]

Thanks to everyone for ya’s responses! Have pretty much done everything suggested, except maybe overfill, maybe be guilty of that. I did replace my original 3-row radiator(ZD Tag) for a 4-core rad, simply because of the history of BB overheating. Do have the 7-blade fan w/o clutch, fan shroud, and 180 degree thermostat. Will print out these suggestions and maybe reverse some of the things done. Waiting to hear from my engine builder, for an answer why he has the overflow plugged off. Also for 169INDY, are you saying the marks on temp gauge is example the 3/4 mark is reading 176 degrees. All along I’ve read it as 220 degrees. Only problem here is my gauge has only 2 marks between cold and hot! Again Thanks, everyone.

[169INDY]

You may be correct.
Are talking a GM Factory installed console gage?
If not we could be looking in our minds at two different things.

I will drag my console out of storage and set up my Temp Sender "Simulator" and Chart a Factory set up and start a new post.

[rich69rs]

Cold = 70 degrees
1/4 Scale = 105
1/2 Scale = 141
3/4 Scale = 176
Hot = 212

When I installed console gages in my '69 RS back in 1993, I made a "quick and dirty chart" by monitoring temperature of the water outlet housing vs. gage reading up to normal and then based on that information, extrapolated what the higher temp values would be.  This has worked well for me over the years.

Richard

[jwbavalon]

My measurements were very close to Richard's.

[DuWayne Ladner]

To 169INDY, yes this is a factory installed gauge in the factory console. Guess I just need to take a pic of gauge and put on here. But think I have found the culprit on loosing fluids. Discovered it yesterday with car on the trailer. And to rich69rs, sorry that’s not my graph at all. Let me just take a pic of gauge and let you re-chart it for me, if you could. Thanks everyone, now hopefully I can find where my leak, is. Thinking heater box, heater hose, or even heater core. Never been changed, that I know of. We’ll see!

[DuWayne Ladner]

Ok gonna have to apologize to rich69rs for comment on his graph for the temp gauge. Exact gauge in my car also. Hope pic comes up or May have to send to your email. Also for other members trying to help on my fluid leak, have a video of the drip drip leak, but still can’t tell where it’s coming from. Thanks.

[HawkX66]

Temp gauge temps...

[DuWayne Ladner]

Thank you Dave, this was my next question. So I will definitely snapshot this and put in my library of my restoration. Thanks again very timely. God Bless.