- Engine:
- G3606 (S/N: 3XF1-UP; 4ZS1-UP)
- G3608 (S/N: 4WF1-UP; BEN1-UP)
- G3612 (S/N: BKE1-UP; 1YG1-UP)
- G3616 (S/N: BLB1-UP; 4CG1-UP)
Coolant leaks around the precombustion chamber's gasket will cause misfire and/or erratic combustion burn times. Inspection is required in order to determine whether the area is leaking. Cleaning of the seat for the gasket is required in order to prevent coolant leaks into the precombustion chamber and into the cylinder.
If a coolant leak is suspected, follow these guidelines.
Detecting a Coolant Leak
A coolant leak will affect the combustion burn time. The combustion burn time may be shorter than the time that is desired or longer than the time that is desired. There is no direct correlation between the severity of a coolant leak and the combustion burn time. Different types of misfire can be identified by the combustion burn time.
- Full misfire has a combustion burn time that is usually greater than 8 ms to 10 ms.
- Erratic misfire has a combustion burn time that is between 3.5 ms and 15 ms.
- A very fast misfire has a combustion burn time that is less than 3.0 ms to 3.5 ms.
Inspecting the Components
To determine the cause of the misfire, perform the following inspections:
Fuel Supply for the Precombustion Chamber
Problems with the fuel supply for the precombustion chamber can also cause misfire. Inspect the fuel lines and the needle valves. Check the needle valves for proper operation and for proper adjustment.
Components for the Combustion Feedback System
False misfire can be created by the components of the combustion feedback system. Inspect the wiring, the electrical connections, the cylinder combustion probe, the cable, the combustion buffer (if equipped), and the integrated combustion sensing module (if equipped). Make repairs or replace components, if necessary.
Ignition System Components
Inspect the components for the ignition system. Make repairs or replace components, if necessary.
Cooling Insert
Use a borescope in order to inspect the cooling insert. Remove the cylinder combustion probe and insert the borescope into the hole for the probe. Look for areas with moisture that can be caused by a coolant leak.
Precombustion Chamber
Use a borescope in order to inspect the precombustion chamber. Remove the spark plug for the suspect cylinder. Insert the borescope into the hole for the spark plug. Look for areas with moisture that can be caused by a coolant leak.
A coolant leak can be caused by problems with the seat or with the gasket. If a coolant leak is strongly suspected, the engine coolant must be drained to a level that is below the cylinder head. Remove the precombustion chamber and the ignition body by following the instructions in the applicable Disassembly and Assembly manual. Closely inspect the sealing surface for the gasket.
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| Illustration 1 | g01010690 |
Surface with heavy deposits | |
Illustration 1 shows a surface with heavy deposits.
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| Illustration 2 | g01010691 |
Gasket with damage | |
Use a new gasket whenever the precombustion chamber is removed from the cylinder. Closely inspect the new gasket before you install the gasket. Illustration 2 shows a gasket that is damaged.
Initial Cleaning of the Seat for the Precombustion Chamber
To help eliminate coolant leaks, proper cleaning of the seat for the precombustion chamber is a critical requirement. Two tool groups are used to clean the surface. The tool group that is used depends on the amount of deposits that must be removed from the surface.
9U-5156 Cleaning Tool Gp
Use the 9U-5156 Cleaning Tool Gp to clean light deposits and medium deposits from the surface. During cleaning, the tool may be rotated by hand. A ratchet, a hand drill, or a similar tool may also be used to rotate the tool. The use of a hand drill is recommended. If a hand drill is used, set the speed between 300 rpm and 400 rpm. Apply a steady downward pressure for a minimum of ten seconds.
The 9U-5156 Cleaning Tool Gp contains several 150-5483 Discs. Change the disc after cleaning the surfaces on approximately seven cylinder heads. Replace the disc more often if the surfaces have significant deposits.
187-6273 Machining Tool Gp
Use the 187-6273 Machining Tool Gp to clean debris and heavy deposits from the surface. The tool will also remove minor pitting. Use the tool according to the Operating Manual, NEHS0790. Experience has shown that a hand drill provides the speed that is required to properly clean the surface. Apply steady pressure to the surface, especially if the surface contains heavy deposits or minor pitting.
Note: After cleaning the surface, carefully inspect the surface. Verify that the cleaning procedure did not generate tool chatter marks. Tool chatter marks appear as radial lines across the surface. Tool chatter marks can cause coolant leaks. If there are tool chatter marks, perform the cleaning procedure again.
Final Cleaning of the Seat for the Precombustion Chamber
Perform a final cleaning of the gasket surface after you have completed the initial cleaning.
- Soak a clean towel with a component cleaner that does not leave any residue. The 138-8440 Component Cleaner is acceptable for such use. Isopropyl alcohol is an acceptable alternative if the 138-8440 Component Cleaner is not available.
- Wrap the towel around a clean 150-5483 Disc .
- Place the disc against the surface and rotate the disc until the surface is completely free of deposits.
Installation of the Prechamber Assembly
Install the prechamber assembly's gasket and the ignition body immediately after the final cleaning in order to help prevent contamination of the surfaces. After installation of the prechamber assembly, tighten the hold-down bolts according to the most recent guidelines. Improper tightening of the hold-down bolts may result in coolant leaks into the combustion chamber.