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1991 560sl / 1987 300TDT / 1995 E300D / 1994 S350D / 1993 300SD /Cummins Diesel PU /2 airplanes
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Discussion Starter #1
So, I've got this overheating issue with my 1995 E300D which is just another excuse to buy more tools!!!
I wonder how accurate these things are. I'll have to figure a way to calibrate it I guess but as it is now...the temp on the cyl head is 67-91 C. the hottest being at the back just above the exhaust manifold, the exhaust manifold measured 112 Deg, C. and the instrument cluster water temp gauge shows 110 Deg C.
I could put my finger in the water in the expansion tank. I will check tomorrow when the ambient temp is around 80 Deg, F.
Always more to learn.
 

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W124 E420 : W220 S500 : W222 S550
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Tips for the "cheaper" variety - like I also own

it does not measure shiny (metal ) surfaces very accurately. Put a piece of thin tape on the surface to help. I have gotten impossible readings on even slightly shiny metal surfaces with my HF (HarborFreight) unit.

try to be as perpendicular to the surface as much possible or else you recieve scatter which is not as accurate.

depending how cheap (well made LOL) the unit is, the beam could produce a very broad beam (field of view) in a very short distance, to combat this, get close to the surface being measured. The "distance to spot" ratio on the cheaper unit is not very good (D:S) - you literally "have" to be close if the surface is small or contoured. however, Our cheaper units do not have "close focus feature" to allow close readings without the addition of surrounding temperaures being added in. So it begs to question - how close?.... I dont know??

The more sunlight, the less accurate the readings also

despite this, they do help..... I would like a nicer unit ........ one day
(Fluke 566/568 would be nice)



So, I've got this overheating issue with my 1995 E300D which is just another excuse to buy more tools!!!
I wonder how accurate these things are. I'll have to figure a way to calibrate it I guess but as it is now...the temp on the cyl head is 67-91 C. the hottest being at the back just above the exhaust manifold, the exhaust manifold measured 112 Deg, C. and the instrument cluster water temp gauge shows 110 Deg C.
I could put my finger in the water in the expansion tank. I will check tomorrow when the ambient temp is around 80 Deg, F.
Always more to learn.
 

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E320/E250 Bluetec Ford F350 6.7l
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36,710 Posts
I am using thermometers quite often and their accuracy is never too good. 3 thermometers in my living room will show 3 degrees variations, while one of them even has 1/10 of the degree, Not that it matters too much in the life as besides measuring your wife's temperature for periods, the 1/10 don't matter.
I do have cheap HF infra-reds but and they are working OK, but also have watch batteries. Than for my pickup I bought the bigger one with laser pointer and use it a lot having no problem to read differential temperature from about 5 feet away. With 9V battery I am not worry about buying expensive batteries often. I have it about 2 years still with original battery.
Some might want to know that measuring tires temperature during stops will let you know if the tire is low on air as the tire will get much warmer than the others.,
 

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1990 Mercedes Benz 300E
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1,336 Posts
I am using thermometers quite often and their accuracy is never too good. 3 thermometers in my living room will show 3 degrees variations, while one of them even has 1/10 of the degree, Not that it matters too much in the life as besides measuring your wife's temperature for periods, the 1/10 don't matter.
I do have cheap HF infra-reds but and they are working OK, but also have watch batteries. Than for my pickup I bought the bigger one with laser pointer and use it a lot having no problem to read differential temperature from about 5 feet away. With 9V battery I am not worry about buying expensive batteries often. I have it about 2 years still with original battery.
Some might want to know that measuring tires temperature during stops will let you know if the tire is low on air as the tire will get much warmer than the others.,
You might be onto something there... maybe have a super-sensitive, far infrared detector array feeding data into a sophisticated heuristic learning algorithm that determines the appropriate proactive response to that time of the month... like "buy Chinese take-out tonight", or "agree about all your failings as a human being for the next 48 hrs" :D
 

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Banned
1991 560sl / 1987 300TDT / 1995 E300D / 1994 S350D / 1993 300SD /Cummins Diesel PU /2 airplanes
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861 Posts
Discussion Starter #6
Tips for the "cheaper" variety - like I also own

it does not measure shiny (metal ) surfaces very accurately. Put a piece of thin tape on the surface to help. I have gotten impossible readings on even slightly shiny metal surfaces with my HF (HarborFreight) unit.

try to be as perpendicular to the surface as much possible or else you recieve scatter which is not as accurate.

depending how cheap (well made LOL) the unit is, the beam could produce a very broad beam (field of view) in a very short distance, to combat this, get close to the surface being measured. The "distance to spot" ratio on the cheaper unit is not very good (D:S) - you literally "have" to be close if the surface is small or contoured. however, Our cheaper units do not have "close focus feature" to allow close readings without the addition of surrounding temperaures being added in. So it begs to question - how close?.... I dont know??

The more sunlight, the less accurate the readings also

despite this, they do help..... I would like a nicer unit ........ one day
(Fluke 566/568 would be nice)
Thanks, That's interesting as I was wondering about the angle, sunlight, distance issues etc... since I got so many differing temperatures on the cylinder head. Do you use masking tape as opposed to black electrical tape?
I do own a VERY accurate digital probe style thermometer that reads to hundredths of a degree in C. and F. If I can find a way to get a good reading with both that will tell me more. For now the resistance of the wire and the cracks from being so brittle seem to be the issue. Even when the car gauge says 118 deg, C. I can easily remove the expansion valve cap and it's not really that hot. Overheating scares me and I am motivated to solve this issue but buying a new glow plug wiring harness ($500+) from the dealer just isn't in the cards...yet.
 

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2001 C320 W203 Black on Black. 1997 E320 W210 Silver (RIP). 1995 E320 W124 Pearl Black.
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Infra-red thermometer will vary by the distance of the object, the closer was more accurate. I notice when I charge my friend's Honda accord AC, standing by the driver window and measure the left and right vent were different, then by walking to the right window and position the IR the same distance I got the same reading. The farther from the object the ambient surrounding temp will affect the reading. By had one TM with the probe stuck in the tranny filler tube and the IR about a foot from the tranny pan got close to same reading, backing the IR out the reading change. Hope this help out.
 

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W124 E420 : W220 S500 : W222 S550
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I use black masking tape....... actually have a roll only for this purpose. The electrical tape is thicker and will act as an insulator to some degree and thus have a reduced temperature.

my oven is about 40 degrees F hotter than the oven dial according to my Temp gun..... we actually had better success cooking with the adjusted temps..... so the gun is not all bad.......


......... masking vs electrical tape?
 
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