automotive diagnostics: measuring coolant temperature in car with temperature gun eT650D

Using an Automotive Infrared Thermometer for Diagnostics

Pole Position in Automotive Diagnostics

One of the most exciting and useful applications of a dual laser temperature gun, such as the ennoLogic eT650D, is as an automotive infrared thermometer. Use the temperature gun to troubleshoot, diagnose and perform routine spot checking of car system performance for everything from brakes to radiators, HVAC system, and engine timing.

As Mark Warren writes in Motor magazine “Squeezing the trigger of a quality infrared thermometer can save hours of frustrating diagnostic time on many vehicle systems. Ready, aim, grab some data!”

EnnoLogic Automotive Infrared Thermometer Special

Easily diagnose, troubleshoot, and perform routine spot checking of your car’s performance.

10% OFF the eT650D IR Thermometer with Coupon Code AUTOMOTIVE10

Quick Summary of Uses

Before we get into the details, here’s a quick summary of how you can use an infrared thermometer for automotive diagnostics:

  • Measure coolant temperatures at the close end of the return line
  • Test for blockages in a radiator
  • Measure belt and pulley temperatures
  • Diagnose cylinder misfires by scanning the exhaust manifold
  • Test your HVAC system by measuring temperatures of inlets, outlets, and supply lines, output vents and condenser
  • Detect excessive heat in brake components
  • Evaluate the heat dispersal dynamics of your brake system
  • Monitor tire temperature on long trips to avoid blowouts

Coolant Temperatures

Measure coolant temperatures at the close end of the return line just before it enters the radiator. Remember that surface temperature will vary slightly from internal temperatures – some 10 to 15 degrees. Pick a spot with small thermal mass, like the top radiator hose connection.

Worried about a blockage in the radiator? These are a little trickier to diagnose. This is because the radiator’s design is to move heat out evenly across the entire radiator by conduction. That is what the design of the radiator core is all about. So you’ll have to move fast. You want to get the coolant and air flow up to their maximum. Then test all the suspected blockage points as soon as you shut the system down. It will only be a matter of moments before the entire radiator is back to a uniform temperature. The cool spots you’re looking for will disappear again.

Cylinders, Misfires, and Engine Performance

When checking overall engine performance or looking to identify ‘hot spots,’ use the dual laser thermometer to read belt and pulley temperatures. This is a much better option than using burns and blisters on your hands as heat indicators!

Engine design, exhaust manifold material and direction of exhaust flow (and therefore, heat) all play a role in how successfully using an automotive infrared thermometer can be.

When diagnosing cylinder misfires, the primary factor will be the design of the exhaust manifold and its relative position with the cylinders.

Cast iron exhaust manifolds distribute heat evenly across the entire area. Due to this, it is nearly impossible to measure individual cylinder temperatures accurately. The newer thin-walled exhaust manifolds produce better temperature gun measurements of nearby cylinders and components of the electrical system.

Heating and Cooling Systems

The dual laser thermometer can test an HVAC system (heating-ventilation-air conditioning) through the inlet and outlet points and all along the supply lines. The laser thermometer can also monitor the re-charging of the air conditioning system to avoid over-charging.

Use the scan feature of the eT650D to watch for a sudden rise in the output to find the moment of full charge of the system.

Use the IR thermometer to test at the output vents, along all lines and at the condenser for a complete diagnosis of the entire system. You can also use it to identify if heating system failures are due to coolant circulation problems or blend door issues.

Brake Systems

The ennoLogic eT6500D can provide invaluable data when it comes to measuring the brake system.

Remember that temperature readings should always be taken for all four wheels. This will provide enough data to know that brakes are operating efficiently side-to-side. Additionally, it can provide information on both the front and rear braking systems.

Excessive heat can indicate excessively worn pads, disks and/or misalignment of these components.

The entire braking system is designed to convert movement into heat.  Conversion starts by applying friction and then works to dissipate that heat. The kinetic energy of the brake’s stopping power is expressed as heat. So, it is simple to identify a non-performing brake with the temperature gun.

You can also study the dynamics of heat dispersal of the brake system. This is done by testing the rate at which the temperature drops after a braking event. You can use the eT650D’s log feature to manual store readings at fixed intervals (e.g., every minute). You can recall those values later when you have time to analyze them.

A lack of heat might indicate that a brake line is either snapped, disconnected or sufficiently blocked. The brake is inoperable in these instances.

EnnoLogic Automotive Infrared Thermometer Special

Easily diagnose, troubleshoot, and perform routine spot checking of your car’s performance.

10% OFF the eT650D IR Thermometer with Coupon Code AUTOMOTIVE10


More Applications of an Automotive Infrared Thermometer

automotive infrared thermometer: measuring truck tire temperature with eT650D temperature gun

These are just a few advantages of using a laser thermometer for automotive systems diagnosis, and there are lots more. Catalytic converter performance, intake air regulation, tires and wheel alignment, testing of the rear differential, and defrost systems are just part of a long list of automotive infrared thermometer applications you can use it with.

When you use an infrared thermometer for diagnosing your car, make sure it is a quality instrument. It should be something that you can rely on and have confidence in. A quality thermometer has features for scanning, minimum, maximum and average temperature tracking, and dual lasers for precise targeting of the measurement area. Your device should also allow you to adjust the emissivity to enable more accurate measurements of metal surfaces, such as brake discs, engine blocks, or catalytic converter components.

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