838666 Volvo.Penta Leak-off line

Illustration 1 g00567675
(1) Solenoid valve (2) Spring (3) Control valve (4) High pressure oil passage (5) Slave piston adjustment screw (6) Master piston (7) Spring (8) Rocker arm adjustment screw (9) Rocker arm (10) Slave piston (11) Exhaust pushrod (12) Exhaust valves (13) Ball check valve (14) Control switch (15) Low pressure oil passage (16) Electrical connectionThe compression brake operates with engine oil which is supplied from the rocker arm shafts. Solenoid valve (1) controls the oil flow in the compression brake housing.When the solenoid is activated, valve (1) moves downward. When valve (1) moves downward the valve closes the oil drain passage. This passage goes to the oil pan. At the same time, valve (1) opens low pressure oil passage (15) to three control valves (3). When low pressure passage (15) is filled with engine oil, control valves (3) are pushed up in the chamber. At this position, a groove in control valve (3) is in alignment with high pressure oil passage (4). The slave piston (10) and master piston (6) are supplied by the high pressure oil passage. Engine oil pressure will now lift ball check valve (13). High pressure oil passage (4) and the chambers behind the slave pistons and behind the master pistons will be filled with engine oil pressure. This pressure moves the master piston downward until contact is made with the engine valve mechanism. The oil pressure is now the same pressure in all the oil passages. This causes ball check valve (13) to seat. The system is completely charged and ready for operation. When the solenoid is activated, the compression brake is ready to operate in approximately 1/5 of a second.
Illustration 2 g00318164
Oil passage Schematic for front Housing (1) Solenoid valve (3) Control valves. (4) High pressure oil passage (6) Master piston (10) Slave pistons (15) Low pressure oil passageWhen the push rod (11) for the exhaust valves begins to move up on the normal exhaust stroke, the rocker arm (9) and the adjustment screw (8) move the master piston (6) upward. As the master piston (6) begins to move upward, the oil pressure increases in passage (4). This causes the ball check valve (13) to close. Since there is a constant increase in pressure with the rocker arm movement, the slave piston (10) is forced down with enough force to open exhaust valves (12) .This master-slave circuit is designed so that the master piston (6) is only moved by the exhaust rocker arm for a cylinder that is on the exhaust stroke. The slave piston (10) opens only the exhaust valves of a cylinder that is on the compression stroke. The valves are opened just before the piston reaches the top center position. The order is shown in the following table:
Table 1
Master Piston-Slave Piston Relationship    
Location of Master Piston     Activates Slave Piston For    
No. 1 exhaust pushrod     No. 3 exhaust valve    
No. 5 exhaust pushrod     No. 6 exhaust valve    
No. 3 exhaust pushrod     No. 2 exhaust valve    
No. 6 exhaust pushrod     No. 4 exhaust valve    
No. 2 exhaust pushrod     No. 1 exhaust valve    
No. 4 exhaust pushrod     No. 5 exhaust valve    When solenoid valve (1) is in the off position, the engine oil supply passage is closed, and the oil passage to the oil pan is opened. This allows the oil that is under the control valve (3) to drain. Spring (2) pushes the control valve (3) to the bottom of the chamber. This position allows the oil from the high pressure oil passage (4) to drain into the chamber above the control piston. Spring (7) now moves master piston (6) up to the master piston's neutral position that is away from rocker arm adjustment screw (8). The time that is necessary for the system to stop operation is approximately 1/10 of a second. The compression brake will not be able to operate now until the solenoid is activated again. Components of the Compression Brake
Illustration 3 g00534221
Compression Brake (Typical example) (1) Rear Housing (2) Front Housing (3) Stud (4) Support bracketThe compression brake consists of two different housings. A housing is installed in each of the valve mechanism compartments above the rocker arm and the rocker arm shaft. Each housing is positioned over three cylinders. The housing is mounted on support bracket (4). Special exhaust rocker arm adjusting screws and exhaust valve bridges are necessary.Note: Only the exhaust valve mechanisms are used in the operation of the compression brake. A spacer is used on top of the valve cover base to permit installation of the valve cover. The compression brake increases the height of the engine. The height increase is 90 mm (4 inch).Both the front and rear compression brake housings consist of the following parts:
three master pistons
three slave pistons
three control valves
one solenoid valve