Laser Thermometer: Great diagnostic tool!!!
06-17-2007, 01:54 AM
#1
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Laser Thermometer: Great diagnostic tool!!!
The other week only one cooling fan was working and my '88S4's temp gage needle was hovering just under the big RED zone. With help from Rennlist, I was able to fix this today. After a spirited 20-mile run, it ran in the "mid zone". This is still a bit too high for me as I suspect that on a hot day, I may still get overheating.
HOWEVER, the laser thermometer that a Rennlister suggested that I buy (someone even sent me the stores' address and sale info!) is a wonderful tool.
Just by pointing the gizmo at different parts of the engine, cooling system, etc. I was able to get instant temperature readings.
For example, I was able to "watch" the passenger's side radiator hose heat up while the driver's side remained cool...then see proof that the thermostat was working when it opened and the temperature quickly changed to drive coolant throughout the system and the other hose heated up. It was about 180 degrees on the pass. side hose and about 170 on the driver's side hose. The radiator was about 165/185 degrees at the top and about 140 degrees at the bottom. I'm guessing that this means that it may be starting to get clogged or perhaps this is this relatively normal as per the cooling cycle?
At any rate, the thermometer was great to use to check transmission temperature, cat converter temp, and so on. This is a diagnostic tool that I wish I'd purchased years earlier. It is Model 91778 Cen-Tech Non Contact Laser gun-type Thermometer from Harbor Freight and was on sale. It worked perfect right out of the box.
Harvey
HOWEVER, the laser thermometer that a Rennlister suggested that I buy (someone even sent me the stores' address and sale info!) is a wonderful tool.
Just by pointing the gizmo at different parts of the engine, cooling system, etc. I was able to get instant temperature readings.
For example, I was able to "watch" the passenger's side radiator hose heat up while the driver's side remained cool...then see proof that the thermostat was working when it opened and the temperature quickly changed to drive coolant throughout the system and the other hose heated up. It was about 180 degrees on the pass. side hose and about 170 on the driver's side hose. The radiator was about 165/185 degrees at the top and about 140 degrees at the bottom. I'm guessing that this means that it may be starting to get clogged or perhaps this is this relatively normal as per the cooling cycle?
At any rate, the thermometer was great to use to check transmission temperature, cat converter temp, and so on. This is a diagnostic tool that I wish I'd purchased years earlier. It is Model 91778 Cen-Tech Non Contact Laser gun-type Thermometer from Harbor Freight and was on sale. It worked perfect right out of the box.
Harvey
06-17-2007, 02:49 PM
#3
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The radiator will be hotter at the top as hot water rises. Also, the inlet is at the top - maybe not so smart. There is a metal deflector slipped inside the inlet whose purpose is to direct more of the flow to the outside and down and prevent the hot water fom just skirting across the top. That deflector is a simple partial tube with an open wedge to be set pointing away from the center of the radiator. I honestly don't know why the radiator fills from the top.
I agree the infrared thermometers have a 1001 uses. However, they can give you some very strange readings at times. They are not too good at measuring temperature in the AC ducts. I get 16-18F regularly, which is not possible, at least in California. Last week I recorded -2F in the center vent. Yeah, sure.
I agree the infrared thermometers have a 1001 uses. However, they can give you some very strange readings at times. They are not too good at measuring temperature in the AC ducts. I get 16-18F regularly, which is not possible, at least in California. Last week I recorded -2F in the center vent. Yeah, sure.
06-17-2007, 03:13 PM
#4
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I'm pretty sure that almost all radiators fill hot water into the top and draw colder water out from the bottom. Convection as Bill points out. The way to see if the bottom is plugged is to look at left and right temps at the same levels, and build a map. The "dead zone" in the bottom will be pretty obvious. The laser thermometer makes this possible. However, it's hard to get good face readings on the radiator while the AC condenser is in place there.
For AC duct temps, I use a cute little digital thermometer from the kitchen-tools store. Sores max and min temps so you don't have to hover over the thing as you work on the system. Two are in service while charging; One for the center vent temp and one for ambient temp. Between the temps and the pressure gauges, you can see how well the heat is transferring across the exchangers. Helps when you need to know how much mud is coating the evaporator, for instance.
Bill- Are you still in L.A. moving your daughter? If you are still here tomorrow (Monday) and need a hand finishing up, PM me. Today is filled with Fathers Day stuff, but there's a schedule gap tomorrow if you need it.
For AC duct temps, I use a cute little digital thermometer from the kitchen-tools store. Sores max and min temps so you don't have to hover over the thing as you work on the system. Two are in service while charging; One for the center vent temp and one for ambient temp. Between the temps and the pressure gauges, you can see how well the heat is transferring across the exchangers. Helps when you need to know how much mud is coating the evaporator, for instance.
Bill- Are you still in L.A. moving your daughter? If you are still here tomorrow (Monday) and need a hand finishing up, PM me. Today is filled with Fathers Day stuff, but there's a schedule gap tomorrow if you need it.
06-17-2007, 03:15 PM
#5
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They are confused by reflective/shiny surfaces. IIRC, it will show lower than actual.
06-17-2007, 04:36 PM
#6
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Originally Posted by dr bob
I'm pretty sure that almost all radiators fill hot water into the top and draw colder water out from the bottom. Convection as Bill points out. The way to see if the bottom is plugged is to look at left and right temps at the same levels, and build a map. The "dead zone" in the bottom will be pretty obvious. The laser thermometer makes this possible. However, it's hard to get good face readings on the radiator while the AC condenser is in place there.
For AC duct temps, I use a cute little digital thermometer from the kitchen-tools store. Sores max and min temps so you don't have to hover over the thing as you work on the system. Two are in service while charging; One for the center vent temp and one for ambient temp. Between the temps and the pressure gauges, you can see how well the heat is transferring across the exchangers. Helps when you need to know how much mud is coating the evaporator, for instance.
Bill- Are you still in L.A. moving your daughter? If you are still here tomorrow (Monday) and need a hand finishing up, PM me. Today is filled with Fathers Day stuff, but there's a schedule gap tomorrow if you need it.
For AC duct temps, I use a cute little digital thermometer from the kitchen-tools store. Sores max and min temps so you don't have to hover over the thing as you work on the system. Two are in service while charging; One for the center vent temp and one for ambient temp. Between the temps and the pressure gauges, you can see how well the heat is transferring across the exchangers. Helps when you need to know how much mud is coating the evaporator, for instance.
Bill- Are you still in L.A. moving your daughter? If you are still here tomorrow (Monday) and need a hand finishing up, PM me. Today is filled with Fathers Day stuff, but there's a schedule gap tomorrow if you need it.
Right on about being better to use standard probe thermometers for AC duct air measurements. The inexpensive infrareds have trouble with the emissivity of the duct surfaces.
We moved a lot of my daughter's stuff home last week and will be going back down to UCLA late today. I appreciate the offer of help, but we've got the moving items paired down to fit in a Mazda Protege 5-door. Her room mates have the furniture covered.
06-17-2007, 11:37 PM
#7
Captain Obvious
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Yes it is a neat too to have. I've used it to find a non running cylinder. Just point to the exhaust ports and the one with the low temp is the non running cylinder.
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06-18-2007, 06:25 PM
#8
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Harvey, when I suggested that I was thinking of watching temps as the car heats up. From cold, you can tell when the thermostat opens, where the warm water flows to and how fast various parts of the rad heat up. This gives some insight to how that various tubes in the rad are flowing. What you did gives some valuable info, but watching how fast parts of the rad heat up can be very instructive.
In my case, the entire passenger end tank heated up relatively quickly, as did the upper tubes, but the lower tubes heated very slowly. Once the car had been running a while the temp difference between upper and lower tubes was smaller.
As Bob says, contact thermometers/thermocouples/etc are much better at low temps. The IR thermometer gets confused easily at low temps, because what it measures is infrared radiation. If something is a lot colder than its environment then it is mostly absorbing rather than radiating IR.
In my case, the entire passenger end tank heated up relatively quickly, as did the upper tubes, but the lower tubes heated very slowly. Once the car had been running a while the temp difference between upper and lower tubes was smaller.
As Bob says, contact thermometers/thermocouples/etc are much better at low temps. The IR thermometer gets confused easily at low temps, because what it measures is infrared radiation. If something is a lot colder than its environment then it is mostly absorbing rather than radiating IR.
