I have an 82 trans am 350 w/ a qjet. It also has a water pump mounted fan, not electric. Anyways ever since I got the car it has run around 210-220 on my temp gauge in the car. It begins to creep up to 230 if I do spirited driving, so I back off.

This was making me uncomfortable so I started replacing cooling components. So far I've replaced the tstat, water pump, lower radiator hose/added a spring, radiator cap, flushed the system, and a new air dam. I removed the old a/c condeser in front of the radiator thinking it may of been blocking air .

​​​None of this has worked. What has me puzzled is even though the car says it's running hot no coolant has made its way into the overflow ( running a 16psi cap ).

So tonight at the parts store I saw a rad cap with a temp gauge built into it. I thought I'd give it a try just to see what the water temp at my radiator was. The thing seemed accurate it read 70 degrees in my house and it rose to 85 (which is the temp today) when I went outside to install it. It read 150-160 after some driving. I figure the water temperature at the rad is around 20 degrees cooler since it's been run through the radiator. My car read 220...

So all that to say. Is it possible that my car is reading 20-30 degrees hotter than what my actual temp is? Is there an easy way to tell?

 

Sounds pretty normal to me.

Sounds like there's nothing wrong with the temp.

Yes absolutely.

Try a cheeeeeeeeeep infrared gun. Even one from HF might accidentally work long enough to get a reliable reading.

The rad cap is on the cold side of the rad; IOW the temp there is THE ABSOLUTE COOLEST SPOT in the whole system. Not representative of engine temp. Sounds like you fell for ad copy that was designed to SELL something, not engineering that was designed to DO something. Sorry, you'll know better next time.

You could also just try swapping out the temp gauge sender. Driver's side head between #1 & #3 plugs. Could be, the engine temp is one thing, but the gauge is being told something completely else.

 

​​​​​​ Thanks for the input. I'm glad there's guys out there like you to help people like me learn. I always thought you wanted to stay under 200. But maybe that's cars with fi? So, if 220 is normal when cruising, where should I draw the line for overheating?

 

These gauges aren't much better than an idiot light. Look at the gauge. Center is 210. The low number is 100, and the high is 260. So on the left side there is a 110 degree spread, and only 50 degrees on the right. So where actually is 230? The gauge is NOT LINEAR.
You could install a second aftermarket gauge, and you will most likely put the sender in the intake manifold. Then you will go crazy because both gauges will never read the same at the same time. And they shouldn't - each is sensing in a different location.
Firebirds do not have a front grille to allow air a straight path into the radiator. You mentioned your AC condenser is not functional. Remove it and install an auxiliary electric cooling fan (keep the mechanical) for when things get a little too hot for your liking. You might want to check and/or replace your fan clutch also.

 

You can also get a mechanical gauge and install it to see if the factory one is accurate. My factory gauge is not accurate. I changed the sender and it is more accurate but still reads high. Also because it is non linear it reads the same from about 180 - 200 then jumps up. IR temp gun and aftermarket gauge tells a different story.

 

Like sofakingdom says. cheap infrared gun, they work well and it will but you at ease knowing that your gauge is off or it's good.
https://www.harborfreight.com/non-co...ing-60725.html

 

I wouldn't bother with a mech gauge, personally. Especially not compared to an infrared.

A mech gauge can do EXACTLY ONE THING, and that's IT. OTOH an IR gun can be used in LIMITLESS situations, not limited to auto applications.

Not to mention cost, ease of "installation", and various other advantages.