I have an issue with my temp gauge reading very high, I have checked the antifreeze, changed to a 180 thermostat, changed the radiator cap, but it's still apparently overheating, and it says after after 5 minutes it gets past 200, I'm wondering if it could just be a bad temperature gauge.

Appreciate any help, Gary.

 

The gauge on my '79 is off badly, even after replacing the sending unit. I installed a $29 aftermarket gauge and use that for now, ignoring the stock gauge.

 

Before you do anything, check that the stock gauge is functioning correctly with an IR thermometer.

 

You need to find out the truth.

Is the car really overheating? or is the indication FUBAR?

then go after the real issue

If it is overheating make sure the POS clutch fan is working ( I just spent two weeks chasing that flaming F-monkey around my garage)

If it just indicates wrong change the sender or gauge and be done

 

200 is not overheating. 230+ would be.

 

When I got it, my 79 L48 was consistently running 210-220. I changed coolant, thermostat(180) and clutch fan. The air flow passages were clean and the air dam was in perfect condition. Timed/tuned good.
My buddy next door suggested rad cleaner and flush. I bought a jug of some type(can't remember the brand) from my local auto parts store.
Added it in, ran it as instructions said to, drained and flushed several times, and put in all new coolant. It now usually runs under 200,,, depending on how hard I push it. I seen it up to about 215 or so but that was after a extended carbon purge down a long lonely empty highway.

 

When my '79 L48 started doing that, I replaced the thermostat, twice. Then I flushed the block with cleaner, opening up the drains on the side of the block, and running until clear, twice. Then I replaced the fan clutch, it looked like the original was still in there. I tried a new water pump, thought that might have contributed to running hot. I bought a new lower radiator hose, making sure it had the steel spring so the hose wouldn't collapse. Somewhere in there I took off the heads and had them rebuilt, no temp diff but it did stop some smoking. Then I replaced the radiator, thinking it may be clogged. I also bought and installed new foam that directs air into the radiator, not around it, no change. I bought and installed a new lower valance and air dam, since mine had a split in the middle, no change. Somewhere in there the carb was rebuilt, no temp change. I also rebuilt the distributor, using Lars' advice and readjusted the timing. Ran better, still hot. I bought a 2004r overdrive transmission, rebuilt that and installed it. Now the temps sit closer to the thermostat temperature than they ever have in the 14 years of ownership. I don't want to point fingers, but that TH350 tranny may have contributed more to my running hot problem than I care to realize. Just throwing that out there in case it helps someone else.

 

yup mine ran 205-210 until I rebuilt the cooling system due to a leak.

quoted just because that is one of the funniest quotes I have read on CF. I may have to put that in my sig.

 

Used a ir thermometer, it's the gauge that's bad, thanks for the help guys. -Gary

 

Are you going to do a factory replacement gauge? I'm in the same situation and am undecided

 

The gauge could be fine. It could be a mismatched sending unit. Aftermarket and replacement OEM sending units are notorious for giving inaccurate gauge readings.
Wilcox has several videos and written instructions on how to check your gauge for accuracy.
Don't just throw parts at the car, trouble shoot and find the cause.

Pete

 

I have '77 with an L-82 and run's at 200, with the A/C on. And thats on hot summer days with the air Temp. 95-100.

 

Has the sending unit been replace, i broke the spade conector off the original and replace it with a box store piece that read real high, checked every thing with an ir thermoeter which told me the sending unit wasnt right. bought an original from a guy who has a corvette salvage up here which fixed it. Good luck.

 

please help my 1978 corvette keeps overheating big issues with radiortot and little gallon connecting to the radiator keep boiling up . thx.

 

Go to Pearl Harbor Freight and get a cheap Infrared Thermometer.....get the car hot and shoot it at the thermostat housing.....compare this with your gauge and make a mental note......
My gauge in my 72' is way off......so I bought this liquid filled mechanical gauge for under the hood......an idea for you. It is fairly accurate....right in line with my Infrared.


Jebby

 

No its not the gauge lol

 

good suggestion..like that idea. Did you put it in the thermo sending unit that was OEM on the intake? Thanks

 

Nah....the sending unit is in the head....
This is a Team G intake.....
I have an oil pressure gauge under the hood too....I am crazy like that....

Jebby