How do you determine engine temp using an IR thermometer?
Thread Starter
Melting Slicks
Joined: Dec 2006
Posts: 2,483
Likes: 1
From: Bay Area CA
How do you determine engine temp using an IR thermometer?
Just purchased a Raytek MT6. It's a nice little tool and I love it.
Where do you have to point it to get an accurate engine temperature?
The reading that I am getting from the block is different from the heads is different from the exhaust manifolds...
Is there one spot that you are supposed to read from or do you calculate a mean from readings from several places?
Where do you have to point it to get an accurate engine temperature?
The reading that I am getting from the block is different from the heads is different from the exhaust manifolds...
Is there one spot that you are supposed to read from or do you calculate a mean from readings from several places?
Pro
Joined: Jun 2002
Posts: 538
Likes: 7
From: Johnsonville Wi
IR gun
An IR instrument reads best from a black (best is a soft black) surface.
You want water temp in this case, so best spot is the upper radiator hose. These instruments will give diff. readings on diff. surfaces, but unless you have one that adjusts for emmisivity it will work accuratly best on black.
For instance, I have a woodstove pipe that has a galvenized section connected to a black section. The black section is 25* higher than the silver section. The reading on the black section was cross checked with a pricey surface temp meter and it was accurate.
Daffy2
You want water temp in this case, so best spot is the upper radiator hose. These instruments will give diff. readings on diff. surfaces, but unless you have one that adjusts for emmisivity it will work accuratly best on black.
For instance, I have a woodstove pipe that has a galvenized section connected to a black section. The black section is 25* higher than the silver section. The reading on the black section was cross checked with a pricey surface temp meter and it was accurate.
Daffy2
Burning Brakes
Joined: Jun 2008
Posts: 1,086
Likes: 1
From: Michigan
Keep in mind that the farther away from the surface you are the wider the area being read. I have a reference scale on mine that happens to be 8:1 ratio. It reads a 1" dia. spot from 8" away and a 2" dia. spot from a distance of 16" etc.
It also looses accuracy if the ambient temperature of the thermometer is considerable difference than the ambient temp in the area you are using it. Example: If you take the thermometer from the warm house say 68*f out to your frozen garage in the winter, say 20*F it will loose accuracy. Allow the guage to heat soak for a while before using.
It also looses accuracy if the ambient temperature of the thermometer is considerable difference than the ambient temp in the area you are using it. Example: If you take the thermometer from the warm house say 68*f out to your frozen garage in the winter, say 20*F it will loose accuracy. Allow the guage to heat soak for a while before using.
Thread Starter
Melting Slicks
Joined: Dec 2006
Posts: 2,483
Likes: 1
From: Bay Area CA
Thanks guys...
I am trying to determine if my temperature gauge inside the car is working right.
The sending unit has a shiny silver painted surface. I'll try the upper radiator hose.
btw.. where does the sending unit pick up temperature from? Does it directly touch the coolant?
I am trying to determine if my temperature gauge inside the car is working right.
The sending unit has a shiny silver painted surface. I'll try the upper radiator hose.
btw.. where does the sending unit pick up temperature from? Does it directly touch the coolant?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
The IR units give different readings at different areas on the engine because those temperatures...well...really are different. If you want to know what the temp of the sump oil is, point it at the oil pan. I'm guessing that you will get fairly equal readings at about any spot on the oil pan where you can point at a flat surface. The value of such a device is that you can spot significant differences between cylinders or at different areas on the exhaust manifolds. Such differences would indicate some cooling problem or some damage occuring at that area of the engine.
Thread Starter
Melting Slicks
Joined: Dec 2006
Posts: 2,483
Likes: 1
From: Bay Area CA
I guess since the sender is what reads the temp for the gauge inside, it may be an accurate place to read from. How about putting a black tape on the sender before reading the temp, so that you are not reading off of a shiny surface?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
The car's temp sender is located in the head between cyl #1 & #3 because the GM engineers wanted to detected head temps that were too high [blocked cooling system or bad pump] or too low [actually, that usually indicates low coolant level and the sensor is just getting a faulty reading]. Either way, the techs thought head temps were the most important place to measure.
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Burning Brakes
Joined: Jun 2008
Posts: 1,086
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From: Michigan
It would be difficult to get a coolant temperature by taking a reading on the sensor screwed into the head. The sensor is in the coolant stream which is a lot cooler than the metal of the heads. Not to mention the exhaust manifold (600*F) is very close to the sensor and will influence the reading.
If you want coolant temp try taking a reading at or near the thermostat housing or the upper hose near the stat housing.
You may also be able to find a cylinder that is not firing by the difference in the temp of the exhaust manifold in that area.
If you want coolant temp try taking a reading at or near the thermostat housing or the upper hose near the stat housing.
You may also be able to find a cylinder that is not firing by the difference in the temp of the exhaust manifold in that area.
Race Director
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Ooops, 08vycpe, types faster.
Melting Slicks
Joined: May 2002
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From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
I've found the intake manifold right next to the head were the coolant exits the head is the best place to get the readings. The T-stat housing being chrome will give false readings on my car.
I have four temp indications and an IR gun.
The sender is also a good place to check, I get very close temp indications form there with the IR gun.
Neal
I have four temp indications and an IR gun.
The sender is also a good place to check, I get very close temp indications form there with the IR gun.
Neal
Burning Brakes
Joined: Jun 2008
Posts: 1,086
Likes: 1
From: Michigan
I've found the intake manifold right next to the head were the coolant exits the head is the best place to get the readings. The T-stat housing being chrome will give false readings on my car.
I have four temp indications and an IR gun.
The sender is also a good place to check, I get very close temp indications form there with the IR gun.
Neal
I have four temp indications and an IR gun.
The sender is also a good place to check, I get very close temp indications form there with the IR gun.
Neal
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
IMCO, you don't. You might get lucky and get readings similar to that of the coolant's on something, but IR pyrometers read surface temps. That's why probe type pyrometers are preferred for tire temps.
Last edited by TheSkunkWorks; Jan 10, 2010 at 07:00 PM.
