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

Visual Inspection

A visual inspection of the cooling system is performed first to identify obvious system defects.

1. Verify that the belts, hoses, hose clamps, radiator caps, surge tanks, fan clutch, fan, fan shroud, and other system components are all present and functioning.

• Inspect the radiator for damage, the cooling fins for obstructions, and the core for translucence. If the radiator core is not too thick, a light shined through the radiator should be easily seen on the opposite side.
• Squeeze hoses to verify that they are not hardened or cracking. Electrolytic action can cause hoses to deteriorate from the inside out. Unusually soft hoses indicate internal deterioration.
• Inspect the accessory drive pulley and belt tensioners for correct operation and alignment.
• Inspect the operation of the heater to verify that warm air blows from the ventilation ducts when placed in heater mode.
• Check for the smell of coolant when the heater is blowing.
• Inspect the heating, ventilation, and air-conditioning (HVAC) module drain tube for leaking coolant.
• Retrieve fault codes.

2. Inspect the level and quality of the coolant in the surge tank and radiator.

• Observe and record the color and condition of the coolant while inspecting the level and quality in order to determine whether the correct type of coolant is in use and whether it is contaminated with oil, fuel, or silicate.
• Measure the freeze protection of the coolant with an appropriate refractometer or hydrometer to match the coolant-type base (ethylene glycol, propylene glycol, or glycerin).
• Using a test strip, measure the additive levels in the cooling system. In anything but NOAT coolant, nitrite/nitrate should be present.
• Verify that the correct level of coolant additives are present. Note that the test strips may be temperature sensitive. Do not use test strips in hot coolant. Allow the coolant to cool in a container for several minutes before testing.

3. Examine the engine for external coolant leaks.

• Inspect the engine oil level and the color of the engine oil to verify that there is no coolant contamination. Sample engine oil and have an oil analysis performed if no identifiable external leaks are detected to account for coolant loss.
• Drain the air tank reservoirs to inspect for coolant leakage into the air compressor.
• Inspect the water pump weep hole for a leakage or dried coolant track.
• Reinspect hoses and clamps for any collapsed hoses, deterioration, leaks, or chaff.
• After pressure testing the engine, pressure test the radiator cap. It should release pressure at no more than plus or minus 2 psi.
• Pressure test the vacuum valve and inspect both the cap’s pressure and the vacuum seals to verify that they are in good condition. Any damage to the seals requires cap replacement.

4. Operate the engine and observe the exhaust smoke color.

• Verify that the coolant reaches operating temperature within an acceptable amount of time.
• White exhaust smoke may indicate coolant leaks into the combustion chamber through a defective head gasket, cracked cylinder head, or leaking EGR cooler.
• With the radiator cap removed or with it on, if possible, inspect the coolant vent lines entering the surge tank to determine whether gas bubbles of excessive size or number are entering the surge tank. Some vaporized steam bubbles should be present from the vent lines connecting the tank to the engine, but excessive bubbling may indicate a cavitated liner or block or a cracked cylinder head.
• Air-operated switches and valves connected to the cooling system, such as water control valves for the cab and bunk heaters, may give a false positive for an internal engine leak. A cracked air compressor casting may give the same indication. Open the air reservoir drain valves while running the engine to eliminate the likelihood of a defective air compressor pressurizing the cooling system. The gaskets and seals on the radiator cap should be inspected for any cracks or damage.