Overheating or bad gauge?

[RETIREDCOPPER]

My '81 seems to be running hot (225) I think. The gauge warms up within 1 mile of leaving home. Although it is hot outside (90's) it seems weird the gauge runs up so fast. I have a new temp sending unit that was just put in but still about the same. It gets to a certain spot then stops. It does not boil over under the hood and the overflow tank levels appear correct. I have not had aVette since the mid 60's (yeah I am that old) and I don't recall them running that hot (if it is). How can I tell if the gauge is off? Thanks in advance....

RICH

 

[jrose7004]

Rich I'm sure Bud will chime in with the answer! Welcome to CAC!

 

[Bob Chadwick]

Retired,

You need to post more information. My 77 will run that hot or hotter if idling in traffic on a hot day. However, at speed it runs between 185 and 200 degrees.

The gauges can run hot on these cars. The only way to know for sure if it is in fact running that hot is to have someone take one of those infrred guns and shoot the upper radiator hose and compare that temp to the gauge.

If it is in fact running hot, depending on when, it could be anythiong from missing seals to a radiator that has outlived its usefullness.

This post needs to nbe moved to the C3 section for more exposure. Hopefully Bud or one of the others will move it over there.

I ran a quick search with the key words engine overheating in the C3 section and came up with some posts that might assist you.

Welcome.

Bob

 

[Rob]

Hi Rich. Welcome to the Corvette Action Center. I'm going to move your thread into the L81 Vette Registry forum...

 

[SIXFOOTER]

#1, corvette gauges are notorious for being WAY off on calibration. The gauge may say 220 but in actuality the engine can be running 195
#2, you need to KNOW what the actual temp is, for $20 or $30 you can get an good IR lasergun to tell you exactly what the temp is. Measure at the sensor same as the gauge and see what the differential is.
The original sender that was color coded to the original gauge may have been changed by a PO and that would acount for the error.
Once you know, you can either get the correct sender for the gauge or keep up with the difference yourself.
That IR gun is a Very handy device, I use mine for all kinds of stuff now that I have one.

 

[22229stingray81]

What about a sticking thermostat? When cold, the engine is supposed to reach a pre-determined temerpature (if it is a 190* t-stat, then it is 190*), then the t-stat will open, and you will hopefully see your engine temp drop again. Then after that it should gradually rise. That is when you know if your engine is overheating, at operating temps. It seems from your post that your t-stat may not be opening correctly. Has it been recently replaced?

-Tator

 

[Hib Halverson]

You can tell if the gauge is off by either connecting the gauge harness to another, known-good gauge or by taking an IR thermometer (ie: a Raytek) and shooting the upper radiator hose or the back of the sensor body. What you see on the gun should be close to what the gauge says. If it isn't, there's aproblem with either the sender, the wiring or the gauge.

If the engine is running at 225, then you need to diagnose a problem with high operating temperature for which there are many causes.

 

[KANE]

My '81 seems to be running hot (225) I think. The gauge warms up within 1 mile of leaving home. Although it is hot outside (90's) it seems weird the gauge runs up so fast. I have a new temp sending unit that was just put in but still about the same. It gets to a certain spot then stops. It does not boil over under the hood and the overflow tank levels appear correct. I have not had aVette since the mid 60's (yeah I am that old) and I don't recall them running that hot (if it is). How can I tell if the gauge is off? Thanks in advance....

RICH

Hib hit the nail on the head: the gauge could be wrong but it is best to check with a known working device.

Regardless of what the gauge says- you should check for the following within the radiator fins just to be safe:
1.) Leaves
2.) Trash
3.) Dirt

Next, you may want to flush your coolant system. If you haven't done this in a while- it is cheap insurance to prevent overheating.

If you are really serious about getting as much gunk out of the radiator you can remove your radiator and take it to a shop to be professionally cleaned and flushed. Many times, these shops will straighten out the fins, recondition the outside, and repair any cracks as well.

 

[Sensei]

If you are really serious about getting as much gunk out of the radiator you can remove your radiator and take it to a shop to be professionally cleaned and flushed. Many times, these shops will straighten out the fins, recondition the outside, and repair any cracks as well.

I did this a couple of years ago and the radiator was no more clean than when I took it to them, just painted black. When I complained, they said the EPA outlawed the chemicals shops used to use to clean the interior of radiators. Now they basically only rinse them out. This sounded lame to me so I called another shop and asked them. They said the same thing. It's a waste of money now-a-days. Just flush it yourself regularly. God bless, Sensei

 

[Gry Ghst]

Do not know the answer but start easy go to you know.That is one fine looking C3.Love the color.

 

[RETIREDCOPPER]

I have checked for gunk and it appears clean. Radiator is good shape, no bent fins and no debris. I did buy an 'I.R. temp detector. It is pretty cool, checked all sorts of things. ANyway I digress... I ran the car for 20 minutes, gauge hit about 210 but the I.R. showed temp at the radiator hose top @ 150. Can my gauge be that far off? It's an '81 and all the other gauges seems OK....thanks in advance.

RC

 

[Hib Halverson]

You can usually find the Raytek MiniTemp for as little as 40 bucks. That's a good IR termometer for checking radiators and hoses.

 

[KANE]

I have checked for gunk and it appears clean. Radiator is good shape, no bent fins and no debris. I did buy an 'I.R. temp detector. It is pretty cool, checked all sorts of things. ANyway I digress... I ran the car for 20 minutes, gauge hit about 210 but the I.R. showed temp at the radiator hose top @ 150. Can my gauge be that far off? It's an '81 and all the other gauges seems OK....thanks in advance.

RC

It is possible for your gauge to be off. Sending units have been known to go bad and so forth because of age- we do have 26+ year old cars!
:L

As long as the temps from reputable tools indicate otherwise... I wouldn't worry too much then.

 

[SIXFOOTER]

Like I posted above, the gauge and the sender are matched by a color coded ballance resistor. You probably have the wrong combination
Your sender was most likely changed at some point and they put in the wrong one

 

[bmotojoe]

This site has a good section on how the center console gauges and there resistors work in conjunction with each other. The ohm readings were taken from an earlier model Corvette but should give you a better understanding on what to look for to get a more accurate gauge reading.
Hope this helps,
Brian
http://www.europeancorvette.com/html/console_gauges.htm

 

[RETIREDCOPPER]

How do you move it to C3 area? I am not a computer whiz to say the least... thanks in advance..
Rich