Hot weather is just around the corner and along with the hot weather will come overheating problems with vehicle engines and in the passenger compartments. Stop and think about the two different cooling systems and how much alike each system is to each other in what they do. Now stop and think about how different each system is in the way they perform their task.
The one thing that is common between an engine cooling and an air conditioning system is they both move heat from a heat source to a place away from the heat source. When working with heat transfer, heat always flows from a hot place to a cooler place, where the heat can be removed from the system. Any time a cooling system doesn’t work properly, there are only two basic things that went wrong; either the heat source is producing more heat than the system was designed to handle, or there is a malfunction in the system. Please keep in mind that the art of the diagnostic process is to get the problem to come to you.
Over the years I have analyzed a lot of cooling system problems and used a lot of different methods to find the problem, but guessing — which leads to tossing parts at a problem — is not a good method to find these kinds of problems. Some of the tools used have been mechanical thermometers, flow meters, scan tools, non-contact thermometers and latex gloves. The main point of using diagnostic tools is to have the ability to gather a lot of accurate information in a short time. This allows the diagnostic technician the ability to come to an accurate resolution of the problem with little time spent.
1999 Nissan Quest
The odometer shows 199,000 miles. The powertrain consists of the 3.3 V6 engine with an automatic transmission.
Now let’s move our discussion of diagnostic tooling technology up a step to using thermal imaging. In years past, the equipment used to capture thermal images has been quite expensive, which prohibited its use in an automotive repair shop. Today this technology is available at a low cost and uses your smart phone camera to provide the thermal photographs (Figure 1). Since the technology is here and quite affordable, how do we apply the tooling to the problem at hand?
A cooling system is designed to move heat from one location to another, so obviously one of the parts must be hotter than the other. In the case of an engine, the engine must be hotter than the lower part of the radiator. To make this easier to understand, I think we need to use an illustration to better understand the concept. Figure 2 shows a schematic of a basic A/C system. By following the colors (red = hot and blue = cold), it is easy to follow the path the heat takes as it is moved from the passenger compartment to the condenser that is mounted in the front of the vehicle.