Infrared Verses Mechanical Gauge

[rfitzpatrick]

I'd been relaying on my Flying Quail and Infrared Thermometer to monitor radiator. Then I installed a 320 degree needle sweep mechanical gauge in my goose-neck. After awhile, I noticed the gauge reading approaching 210 and would pull over to rest -- adding water which it didn't need (this should have been a clue). Today took another run, temps went to 200 but this time I shot the top of the radiator outside the Pickup and found it to read 170. There's a 30 degree difference between the gun and the gauge so it seems --
is this possible? I didn't buy my gauge from a Model A Vendor, 'cause I wanted a 320 degree needle sweep which I'v found not available.

Anyway -- will replace gauge again, from an A Model Vendor -- so, am I on the right track here?
Thanks Guys

[wmws]

I would test the gauge in a pot of boiling water. That will tell you how accurate it is.

[GerryAllen]

I use an old meat thermometer from my wife's collection of kitchen stuff. It works well enough to verify what the actual temperature is.
I go for a nice 20 mile drive, come home pop the meat thermometer in the radiator and have found it to work well.
Gerry, Birch Bay WA

[Chuck Sea/Tac]

Originally Posted by GerryAllen

I use an old meat thermometer from my wife's collection of kitchen stuff. It works well enough to verify what the actual temperature is.
I go for a nice 20 mile drive, come home pop the meat thermometer in the radiator and have found it to work well.
Gerry, Birch Bay WA

That is not going to be accurate because,
A) model As water runs below the baffle.
B) heat rises, so the air vapor your measuring will increase temperature after you stop. Engine running or not.
Just a note of caution, if you are overheated, which obviously your not, and you don’t notice it. When you open the radiator cap, you will be greeted by an explosion of steam and boiling water.

[eagle]

[QUOTE=
Just a note of caution, if you are overheated, which obviously your not, and you don’t notice it. When you open the radiator cap, you will be greeted by an explosion of steam and boiling water.[/QUOTE]

Nonpressurized system. No drop in pressure when opening the cap. No "explosion".

[Chuck Sea/Tac]

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Originally Posted by eagle

Nonpressurized system. No drop in pressure when opening the cap. No "explosion".

Bull crap had it happen at the top of mount baker. I’ve seen a home built tractor without a radiator cap shoot water 5’ in the air. It was running about 1200 rpm though.

[Synchro909]

Originally Posted by Chuck Sea/Tac

Bull crap had it happen at the top of mount baker. I’ve seen a home built tractor without a radiator cap shoot water 5’ in the air. It was running about 1200 rpm though.

I used to think that because the Model A cooling system is not pressurised, it wouldn't erupt if I removed the cap whien it was hot. How wrong I was! I scalded my hand and crated quite a spectacle.

[7_Zero]

Originally Posted by Synchro909

I used to think that because the Model A cooling system is not pressurised, it wouldn't erupt if I removed the cap whien it was hot. How wrong I was! I scalded my hand and crated quite a spectacle.

Same here! Actually happened to me twice! You'd think I would have learned the first time. Started pouring water over the radiator and putting a towel over the cap before opening it. Have a new radiator now and overheating is a thing of the past.

[gilitos]

The infrared thermometers like Harbor Freight (and others) sell are only accurate reading a flat black surface. They have significant error reading temp on any other surface; you have to calibrate it on any other color or reflectivity surface. A quality thermometer will be more accurate. Trust the thermometer before the gun.

[Chuck Sea/Tac]

The infrared works great for shooting the bare radiator. Don’t stick it under the hood with the engine running. Electrical interference can damage it.

[30 Closed Cab PU]

Originally Posted by Chuck Sea/Tac

The infrared works great for shooting the bare radiator. Don’t stick it under the hood with the engine running. Electrical interference can damage it.

Electrical interference can damage, or may just scramble the readings.


Better more expensive temp guns are designed not to have this issue. I have a cheap one, but had to borrow a Fluke brand gun from the Mechanic I use for my other vehicles.


If you turn off the motor and take readings immediately, you can still get some approximate readings in the motor bay, but may not be 100% accurate.