1. Maintenance of Cooling Systems

1.2. Pressure Testing the Cooling System and Checking for Leaks

LO 11-08: Outline maintenance procedures and identify tools and methods used to perform maintenance on a diesel engine cooling system.

 

Pressure Testing the Cooling System and Checking for Leaks

Pressure test the cooling system, particularly if there is a complaint about the loss of coolant. Pressure testing the cooling system is an effective way to locate external and internal coolant leaks. High cooling system pressure causes coolant to leak out much more quickly from a crack, hole, leaking gasket, or seal, which makes leaks easier to locate. Adding dye to the engine coolant allows coolant leaking into heat exchangers to be more easily identified with a UV light. The dye must be added to and circulated in a warm engine before inspecting for leaks.

Loose hose clamps often cause cold leaks and can be detected more easily when the engine is off. Other leaks, such as head gasket leaks and those resulting from cracked or porous castings, may only be detected after the engine is operated under load at operating temperature. The cooling system pressure cap should also be tested because a defective or leaking cap will fail to pressurize the cooling system, resulting in coolant loss Figure 72. To pressure test the cooling system and check for leaks, follow the steps in Skill Drill 11-1.

 

  Technicians Tip  
  If you need to replace a pressure cap, use only a cap with the recommended pressure, not a cap with higher pressure. Diesel engines often use caps with lower pressure in order to protect the engine oil from overheating in the oil cooler. Caps with lower pressure will allow coolant to boil at a lower temperature, enabling the escaping steam to carry away excess heat.  
  Fig11_72

FIGURE 11-72: Pressure testing a radiator cap.

 

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