LO 11-8 Outline maintenance procedures and identify tools and methods used to perform maintenance on a diesel engine cooling system

Maintenance of Cooling Systems

This chapter on cooling systems is lengthy not only because of the wide range of technology used in cooling systems but also because of the disproportionate influence the cooling system has on potential engine failures and maintenance. Approximately 40% of all engine maintenance or breakdown is related directly or indirectly to cooling system maintenance, so technicians need to be familiar with common service practices and diagnostic procedures.

Service Tools

A properly trained and experienced technician will use special tools for diagnosing and servicing the engine cooling system. These tools include Figure 70:

A	B		FIGURE 11-71: A coolant refill tool draws a vacuum into the cooling system and uses the negative pressure to refill the cooling system without forming any air pockets.
FIGURE 11-70: Common tools needed to service cooling systems: A. Pressure tester. B. Refractometer.

• Coolant system pressure tester: A pressure tester is used to apply pressure to the cooling system in order to identify the source of external coolant leaks. Under pressure, coolant may also leak internally to the combustion chamber, intake or exhaust system, air compressors, and EGR coolers and also into liquid air charge coolers or lubricating oil.
• Hydrometer: A hydrometer is used to measure coolant density in order to determine its freeze protection. When measuring the specific gravity of the coolant, use a purpose-made hydrometer designed specifically for the type of antifreeze base.
• Refractometer: A refractometer is used to measure coolant concentration and freeze protection by evaluating the fluid’s refractive index (ability to bend light). This refractometer can be used with ethylene glycol– and propylene glycol–types of coolant.
• Coolant test strips: These strips are used to quickly evaluate a number of variables, such as the coolant pH, percentage of nitrite or nitrate, presence of corrosion inhibitors, and even freeze protection. The capabilities of the strips are price sensitive, with more features making the tests proportionately more expensive.
• Coolant tracing dye: To identify coolant leaks, tracing dye is sometimes added to the coolant. Using an ultraviolet (UV) light source (black light), the location of a leak is easily identified because the dye becomes fluorescent under the black light.
• Infrared thermometer: This is a noncontact thermometer used to measure the actual surface temperatures of various components throughout the cooling system. It is helpful to quickly identify under- or overcooled components in order to pinpoint the location of system flow restrictions.
• Thermometer: A thermometer is used to measure the temperature of air exiting the heating ducts.
• Voltmeter: A voltmeter is used to identify electrical problems in various areas, such as cooling system sensors and fan control circuits.
• Belt-tension gauge: This gauge is used to check belt tension in older V-belt drive systems. Loose belts slip and prevent proper circulation of coolant.
• Serpentine belt-wear gauge: These gauges are used to check whether the serpentine belt grooves are excessively worn, which allows the belts driving the water pump or fan to slip.
• Alkaline cleaning agents: These agents are used to clean cooling systems of oil and fuel contamination. They are generally more effective than powdered nonfoaming detergents. Use of any particular cooling system cleaners must be checked to verify that they are safe for aluminum radiator and heater cores. These types of cleaners are also capable of removing silicate deposits.
• Mild, acid-based cleaning agents: These agents are used to safely remove rust, corrosion, scale, and solder particles without disassembling the cooling system.
• Electronic service tools (ESTs) : Commonly called a scan tool or used with a laptop running OEM or other software, these tools activate the cooling fan through bidirectional communication. Fan timers are used to control minimum fan run-time speeds to reduce on/off fan clutch wear and are adjusted using OEM software. Diagnostic trouble codes (DTCs) related to the cooling system are read and cleared using OEM software
• Coolant refill/air purge tool: This tool is used to refill a cooling system after it has been drained. Many of these tools are universal, using a venturi and compressed air to pull a vacuum into the entire cooling system. When evacuated, the negative cooling system pressure draws in coolant from a container and does not permit air to enter the system. This method ensures that no air pockets are left in the cooling system as a result of refilling. Use of these tools is mandated by some OEMs in order to prevent coolant voids in places like the EGR or oil cooler and potential for the absence of coolant to create hot spots that burn and damage those components after start-up Figure 71.