Using an IR temp gun to check engine temps?
 

Where is the most accurate place to aim the gun for accurate temps? Its all over the map on temps. If I aim at the thermostat housing I get say 210, if I aim at the radiator hose I get 180, if I am at the hot side of the radiator I get 180 or so, then the cool side of the radiator is 170...

Which one is the best to use...My factory temp gauge works but I think it reads too cool so I just want to check it before I melt it..
TIA

I use the thermostat houseing myself. Factory temp gauge matches it perfeclty even though it's sensor is in the head. :cheers:

if you want to confirm your temp gauge, aim at its base. this will confirm your in dash gauge. keep in mind that different materials reflect light differntly. a chrome water neck will show 10 degrees differnet than a painted one will. also alumunim intakes are about 5 degrees different than hoses. you can put some masking tape on the objects of interest and shoot a temp off the tape, this usually gives more consistent readings since the refracted light is is almost identical off the tape.

Thanks guys, I am just trying to figure out how hot my engine runs. It has always ran cool and the temp gauge shows it runs REALLY cool. It has a 160* stat in it and it most of the time when the AC is off, it runs about halfway between the "100" and the first slash mark(the one thats between the 100 and 210). I believe that first slash mark is supposed to be 180 or so.. With the AC on, it often runs right at that slash mark. Today when it was at that slash mark, I shot the thermostat housing and it was reading 210* but I could EASILY skew the reading by holding the button longer or aiming it at a slightly different spot.

Same thing with the radiator hose, if I got 210 at the stat housing and go up about 2-3" on the hose, I might have 180, then closer to the radiator but still shooting the hose it would be 170.

I am just trying to get an idea what its really running because idling with the AC on for a while, sometimes it gets close to 210 on the gauge and I have a feeling its way hotter then that.. BUT it never pukes fluid on the ground so...who knows.

Maybe I should just plumb a mechanical temp gauge into the intake for a day just to compare the gauges.

The gauge does not really give you "Engine Temp". It gives you an interpretation of the temp at the sensor. GM ut the sensor on the hottest part of the engine between the 1st and 2nd cylinders on the head. To verify the temp gauge put your IR gun on the sender and note the gauge reading against the gun. The gun is probably a LOT more accurite than the gauge. You could also use a OHM meter and chart the resistance readings on the sensor and a range of temps. Use that info to recalibrate the gauge. There is a Lot of variance on the temp sensors and gauges since they are not mil spec. Hope this helps

Sixfooter, I did try shooting the sender itself but I think the headers add too much heat to it. It read like 240* within 10 mins.

See thats what I was thinking about the IR gun, its giving you the surface temps of an object, its not actually hitting the water in the engine. More then likely the thermo housing is about the best place to get a reading since its aluminum and not heak soaking like the cast iron will. Even so, my gauge was showing 180* when the temp gun was showing 210*...... So I would HATE to see what it was really running when my gauge was showing 210*:ack:

The funny thing is though, the car never "smells" hot nor does it ever puke coolant on the ground after I shut it off(no tank).

I think I am gonna go buy a mechanical gauge for comparison. I would really hate to over heat this thing when running the AC in stop and go traffic this summer.:crazy:

The coolant temp should always be less than the metal its running in because it is not 100% effecient and the cooling system is a process.
What is it your trying to acomplish?

Well I was trying to get an idea of how hot the engine really runs. Reason it because most of the time the engine never reaches the 1st mark on the gauge after 100*, its usually only a couple of needle widths past the 100*. With the 160 stat I figure its running at least 170* at that point so I have always just assumed it ran cool. Well last night it hit 210 on the gauge which I was worried could be 220-230 or more since the factory gauge reads so "cold". Thats why I bought the heat gun was to test it out but I figured out the heat gun is really only good for surface temps.

This morning I went and bought a good iequiis mechanical gauge with a wide sweep in the 160-240 range. I put it in the intake and ran it into the car and I just held it while I drove. At low temps, the factory gauge is way off like I figured. The factory gauge would be barely above 100*, like 2-3 needle widths past, yet the mechanical gauge read 170*. BUT when the factory gauge would get to the 1st mark between 100 and 210,(which I figured was 180*) the mechanical gauge showed 185-188*. So they are getting closer. Then when the factory gauge would get slightly past the half mark, the mechanical gauge would read 190-195.

So in some areas they are pretty close. No doubt the factory gauge is not near as quick or accurate as the mechanical gauge. Once I let it idle for about 15 mins in my driveway right after a highway run. I had the ac on and the factory gauge read about 205* or so and the mechanical gauge hit 215*. It seemed to stabilize there and I didn't let it idle any longer then 20 mins with the AC on. All in all, the car runs pretty cool considering the load that AC puts on it. I am going to leave the mechanical gauge in the car but I hid the wire and the gauge itself up behind the console, right behind the radio access plate. If I need to compare them, I can just pull the gauge out all the way to my seat. Otherwise its hidden to the public. On another note, I stuck a new thermometer into my vent today and used my old one also, my AC got down to 38* on my old one and 40* on my new one. Its pretty sweet to have an old car with cool ac..