Coolant loss in a Paccar MX-13 engine can be a frustrating issue. One potential culprit is the air compressor introducing air into the cooling system, leading to excess pressure and leaks. This guide outlines a step-by-step diagnostic process to pinpoint the source of the problem, focusing on potential air compressor issues and other related failures.
Identifying the Source of Coolant Loss
The first step is to determine if combustion gases are present in the coolant. This is done using a combustion leak tester, also known as a “block tester.” The tester uses a fluid that changes color (typically from blue to green) when exposed to combustion gases. If the test is positive, the issue lies within the engine itself. If the test is negative, the air compressor may be the source.
To check the air compressor, disconnect its discharge line. This isolates the compressor and prevents it from pressurizing the cooling system. If air bubbles and pressure in the coolant decrease significantly after disconnecting the line, an internal air compressor failure is likely the cause. Continued bubbling indicates the problem lies elsewhere.
Other Potential Culprits: A Systematic Approach
If the air compressor isn’t the issue, or if combustion gases are present, a systematic elimination process is necessary. The following components should be investigated in this order:
1. EGR Cooler Leaks
The Exhaust Gas Recirculation (EGR) cooler can develop internal leaks. To test it, perform a pressure test both cold and after submerging it in hot water to simulate operating temperatures. Consult the service information for the correct procedure and tooling. Leaks are often more apparent when the metal expands due to heat.
2. Leaking Injector Sleeves
If the EGR cooler tests good, with all six injectors removed, pressurize the cooling system. Inspect the area around the top of each injector sleeve for coolant leaks. Use a borescope or flashlight to examine the cylinders for coolant dripping onto the pistons. Leaking injector sleeves require cylinder head replacement, as they are not serviceable.
Note: If cylinder head replacement or further troubleshooting is required, consulting an authorized OEM Service Center is strongly recommended. Their specific instructions will supersede these guidelines.
3. Cylinder Head Gasket Failure
If no injector sleeve leaks are found, remove the cylinder head. Inspect the engine block, cylinder head, and head gasket for corrosion, scorching, or discoloration. Discoloration on the head gasket and liner flange, where coolant and combustion gases mix, indicates a head gasket failure. Measure and record the liner heights, referencing the “Height Cylinder Liner, STD (Basic Assembly)” section in the service information and comparing them to specifications.
4. Cylinder Head Cracks
Inspect the removed cylinder head for cracks, particularly between the valves. These can be difficult to see, so using a liquid penetrant like Magnaflux is highly recommended. Photograph any detected cracks. Cracked cylinder heads are not serviceable and require replacement. Refer to “Check Cylinder Head, Engine (Basic Assembly)” for detailed inspection and pressure testing procedures.
5. Cylinder Liner Cracks
Visually inspect the inside of the cylinder liners for cracks, preferably with the pistons at bottom dead center. Magnaflux can also be used here.
Utilizing Diagnostic Software
Paccar Davie 4 diagnostic software is the factory-recommended tool for in-depth diagnostics and troubleshooting. It provides comprehensive information and functionalities beyond the scope of this guide.
Seeking Expert Assistance
Document all findings, including pictures and measurements. This information, combined with OEM software updates, allows your Volvo/Mack Service Center and RESM (Regional Service Manager) to provide the most accurate diagnosis and optimal repair strategy for your specific situation.
