Usage:
Coolant loss can occur in various ways in installations of 3406B Truck Engines. Needless replacement of expensive components can occur when trying to troubleshoot a loss of coolant complaint. Consider the following components as you troubleshoot a loss of coolant complaint.
OEM's (Original Equipment Manufacturer's) Installation Of Radiator Shunt Line
Reference: Know Your Cooling System SEBD0518, Page 22, "Check for Air, Gases, and Steam in the Cooling System. " Truck Engine Application and Installation Guide LEBT8121, Page 28.
Reference: Truck Engine News, February 1990, Page 2, "New Water Temperature Regulator Used. "
The line from the upper chamber of the radiator (or expansion tank) to the SUCTION SIDE of the water pump can be installed incorrectly. See Illustration 2 of the Reference Article, for correct location of shunt line. In the following illustration of a 3406B water lines group, Plug (1) is recommended for the shunt line. Plug (2) will work but is normally used for the heater return hose. The shunt line needs to have a continuous slope down from the expansion tank to the water pump housing.
NOTE: The cooling system requires at least a 6% expansion volume above the system "Full" mark.
Plugs in water lines group for installation of shunt line.
OEM's (Original Equipment Manufacturer's) Installation Of Head Vent Line
Reference: Truck Engine News, February 1990, Page 2, "New Water Temperature Regulator Used. "
The vent from the front of the cylinder head to the radiator top tank or expansion tank must have a 4.8 mm (.19 ") restriction (or be fitted with an 8N9071 Check Valve) to prevent excessive coolant flow and possible engine overcooling. Flow from the engine to the expansion tank can give the FALSE impression of combustion leakage to the cooling system.
Head Gasket
Reference: Threaded Fasteners SEBV0545, Page 6.
Reference: Truck Engine News, August 1989, Page 1, "Improved Head Gasket Used; Summary of Earlier Gaskets and Service Tips. "
Combustion gas can leak across a fire ring WITHOUT leaving visual damage. This leakage can lead to liner seat erosion, block erosion or failure of a water ferrule (failure that may or may NOT cause coolant leakage from the spacer plate joint). Head bolt shanks that are damaged by combustion should be polished with a Scotch-Brite ® wheel to remove any surface carbon or corrosion. Do NOT reuse head bolts with "serious" surface damage as per the Reference.
Cylinder Head
Truck Engine News, July 1987, Page 7, "High Alloy Cylinder Head Improved. "
This IS NOT usually the cause of coolant leakage on 3406B ATAAC Truck Engines. The 7W0006 Cylinder Head used on this engine has a VERY LOW, if any, incidence of "unseen" inlet port cracking. (This is not the case with the former 7W2200 Cylinder Head that was used on most 3406B Truck Engines with jacket water aftercooling). Verify suspected leakage by looking for coolant deposits in the inlet port or inlet valves, OR conduct a leakage test on the cooling system AFTER replacement of the head gasket.