AVDS-1790-2CA Engine

NSN Lookup provides servicing, maintenance, repair, overhaul and remanufacturing of the AVDS-1790-2CA engine. The state of the art facilities provide for high-volume engine rebuild and comnputerized dyno testing of the AVDS-1790-2CA Engine. The dynamometer testing of the engine provides engine break-in and performance testing to ensue that the engine is ready to run when installed into the vehicle. After warm-up the engine may immediately be used at up to full power in all scenarios. This is most commonly termed a "Battle-Ready Engine". The extensive testing (over 17 hours) ensures zero infant mortality and an extended life expectancy.

The AVDS-1790-2C Engine was upgraded with the addition of the "Clean-Air Package" with the introduction of the AVDS-1790-2CA Engine. The "A" in the model number indicated the clean-air package upgrade.

The Clean-Air Package operates by employing an air pressure differential switch on each turbocharger. When foreign object debris (FOD) enters the engine air intake system such as dust, water spray or insects, the air pressure differential within the intake housing of the turbocharger (cold housing) changes and is sensed by a switch. When the air pressure differential switch is activated, a solenoid is operated to eject a significant volume of the incoming air with the principle that the FOD will be ejected into the exhaust through a baffling horn before entering the engine. This system is best employed in dusty desert conditions and can be quite successful in its operation, especially at higher power load conditions. The clean-air upgrade has been so prolific that it is now accepted practice for non-upgraded engines in the M48/M60/M88 Series to fit replacement turbos made for clean-air to the non-clean-air engines with pipe plugs fitted in the turbo cold housing air flow sensor hose taps to minimize spare parts inventories.

The Clean-Air Package upgrade kit consists of many items, including:

• Replacement Exhaust Outlet Elbows
• Replacement Turbochargers
• Ejection Plumbing
• Pressure Sensitive Switches and Hoses
• Mounting Brackets and Hardware
• Replacement Engine Wiring Harnesses

When the AVDS-1790-2CA Engine and supporting systems are maintained with precise detail to the PMCS (Preventative Maintenance Checks and Services), an engine can be expected to last in regular service for 1000s of Hours.

The primary cause of failure in the AVDS-1790-2CA Engine is thermal damage (overheating). Thermal damage inevitably begins with a fluid leak in the engine compartment of the vehicle. This fluid leak can be lubricating oil, fuel or Hydraulic Fluid. The interior of the engine bay is painted white so that leaks can be identified quickly. Oil Leaks from the engine occur from two sources, seal and hose failure or impregnation of lubricating oil from inside the combustion cylinders which leaches into the aluminum cooling fins of the cylinders. The failure mode is when fluid contaminates the cooling surfaces of the cylinder heads. The cylinder heads are air-cooled and the substantial un-filtered air flow over them carries debris which builds up on contaminated surfaces. The contamination reduces the thermal efficiency of the cylinders until the maximum operating temperatures are exceeded. When thermal failure occurs, it generally manifests itself as cylinder seizing which promptly breaks a connecting rod with the remaining "stub" rod penetrating the crankcase. The primary mode of elimination of this failure mode is to regularly clean the engine with hot pressurized water and detergent.

The second most prominent failure mode of the AVDS-1790-2CA engine is loss of lubrication causing bearing damage and piston seizing. The lubrication system of the AVDS-1790-2CA is quite substantial with four lubrication oil pumps, baffled multi-compartment oil pan, oversized oil filters, filter bypass valves, thermostatic flow control to the oil coolers and an oversized oil pressure regulator scroll valve. When servicing the AVDS-1790-2CA lubricating oil filters, a drain valve must be opened on the oil filter housing. After service, this drain valve must be re-tightened to a specific torque for the correct operation of the engine. A common mistake is to not tightened this valve or over-tighten the valve crushing the internal sealing surfaces and causing an internal leak. When this valve is not functional, low engine lubrication oil pressure may occur, or worse, normal engine oil pressure but reduced lubrication volume. A reduced lubrication circuit volume is rarely noticeable by the operator as the oil pressure would be normal. The oil pumps are working to maintain pressure by over-pumping yet up to 60% of the oil can be flowing through the bypass in the oil filter housing rather than flowing through the normal lubrication circuit. This causes bearing and cylinder failure very quickly without obvious visual clues to the failure. NSN Lookup sells replacement oil filter housing decals with the servicing instructions to help prevent this failure, click here for details:

AVDS-1790 Oil Filter Service Instructions Decal