brought to you by Marine Parts Express
Adapted from the Volvo Penta Diesel Service Training Manual
Table of Contents
The engine has two cylinder heads each covering three cylinders. Each cylinder head is attached to the cylinder block with 20 bolts (M11)
The cylinder head material is special alloy cast iron. The cylinder head gasket is made of solid steel.
The cylinder head face has sealing grooves formed by two concentrical wide grooves sunk into the cylinder head face directly above the cylinder liner collar. These grooves adjust the sealing surface area so that the required sealing pressure is obtained without the need for height tightening torques with the risk of deforming the cylinder liner recess in the block. There is also a groove for the cylinder liner’s flame barrier.
The cylinder head bolts are tightened by a combination of torque and angle tightening.
The cylinder block is a one piece casting of special-alloy cast iron. The combustion pressure force in the cylinder head bolts is transferred via reinforced sections in the cylinder block walls direct to the main bearings.
The camshaft bearings are line-bored to the correct dimension after assembly.
The pistons are made of light-alloy. The upper compression ring, which distributes most of the heat conducted via the piston rings is located in a special-alloy cast-iron ring carrier, integrally cast into the piston. This gives the piston ring groove a long life, despite the heat stresses.
The piston ring grooves for other piston rings are machined directly in the piston.
The engine combustion chambers are contained completely in the piston crown. Piston and liner are supplied as parts only as a complete kit.
The cylinder liners are replaceable and of the “wet” type. They are made of cast iron and centrifugally cast. The cylinder liners are fitted with a so called “flame barrier”. The flame barrier, which locates into a groove in the cylinder head, reduces the stresses on the cylinder head gasket.
The cylinder liner’s external sealing is done by four rubber O-rings. The three lower rings are located in machined grooves in the cylinder block. These rings are made of different materials. The lower sealing ring (violet) is made of fluoric rubber (FPM). Both upper sealing rings in the lower liner seal are similar and made of Ethylene Propylene Diene Monomer rubber (EPDM).
The camshaft is journalled in seven bearings. The axial clearance is determined by the camshaft gear, the shoulder on the front bearing journal and the thrust washer bolted to the front surface of the block.
The drive gear assembly consists of cylindrical gears with helically cut teeth.
The injection pump and camshaft are driven by the crankshaft via an intermediate gear. The engine’s lubricating oil pump is also driven by the crankshaft via an intermediate drive gear.
Apart from the camshaft, the camshaft gear also drives the sea-water pump drive gear (marine engines), as well as air compressor, if fitted (optional equipment) is also driven by the camshaft gear.
The crankshaft is journaled in seven main bearings. The axial bearing consists of thrust washers located at the centre main bearing. The crankshaft is balanced both statically and dynamically. The front end of the crankshaft has a polygon profile and the rear end has a flange to which the flywheel is bolted.
The crankshaft is nitro-carbureted. Provided that the shaft does not need to be straightened before grinding, grinding to max. 2nd undersize can be done without a renewed nitro-carburetion.
The main and big –end bearings consist of indium-plated lead-bronze lined, steel shells. These bearings are precision manufactured and are ready for fitting. Five over-sizes are available as parts. The thrust washers for the crankshaft axial bearing are available in three over-sizes.
The connecting rods have an l-profile and are drilled for pressure lubrication of the gudgeon pin. Since the connecting rods have diagonally split bearing recesses, the rods can be removed through the cylinder liners when the engine is being disassembled.
The gudgeon pin bushes are of steel with a bronze alloy facing.
The connecting rods for the 71 series have trapezoidal gudgeon pin end to obtain larger effective bearing surface against the gudgeon pin.
The vibration damper consists of a hermetically sealed housing in which there is a mass made of steel with a rectangular cross section. This mass (the damper ring) is carried in the centre on a bushing and is surrounded on all other sides by a viscous liquid (silicone).
The flywheel is bolted to a flange at the rear end of the crankshaft. It is statically balanced and completely machined. The starter ring gear is shrunk onto the flywheel.
The engines are equipped with a force-feed lubrication system with oil filters of the full-flow type and an oil cooler.
The oil pump is situated at the front of the oil sump and is driven by the crankshaft via an intermediate gear.
All bearings and gudgeon pins as well as the valve mechanism and the timing gears bearings are pressure lubricated.
The timing gears are intermittently lubricated from the intermediate gear bearing journal which is connected to the main oil gallery.
The fuel injection pump and turbocharger are pressure lubricated. The air compressor, if fitted, is also connected to the engine’s pressure lubrication system.
The lubricating oil pump is of the gear type. The pump sucks oil through the strainer and suction pipe into the pump’s suction side.
The lubricating oil strainer, which is a steel gauze strainer, prevents large particles which may be present in the oil from entering the pump.
Oil is fed from the delivery side of the pump, partly through the lubricating oil filter and out to the different oilways, and partly through the oil cooler (and further to the piston cooling nozzles on those engines with piston cooling) and back to the oil sump.
The lubricating oil pressure is limited by a relief valve. The valve is located in the lubricating system immediately before the oil filter and is fitted in the filter bracket on the cylinder block’s right hand side. The valve opens at an excessively high pressure and feeds oil back into the sump.
The cooling function of the lubricating oil is used for TD71, TID71, and for TAMD61 and TAMD71 as the pistons are cooled by the oil.
This cooling gives a marked reduction in the piston temperature, which in turn helps to provide a longer life for the piston rings and liners, less risk of carbon build-up on the cylinder surface and lower oil consumption.
From the oil pump, oil is supplied both via the lubricating oil filter to the engine’s different lubricating points and also via a spring-loaded valve (piston cooling valve) through the oil cooler and out to fixed nozzles, one for each cylinder. From the nozzles, oil is injected up against the underside of the pistons, where the oil spray for each piston is guided into a drilling at the bottom of the piston when the piston is near the bottom dead centre. Through the channel in the piston, the oil is sprayed up to a cooling loop in the piston’s/ upper section. After the oil has circulated round the top of the piston. After the oil has circulated round the top of the piston, it leaves through the drain channels carrying away heat.
The oil cooling valve (TD61, TID61) and the piston cooling valve (other engines) control the oil flow to the oil cooler and further to the piston cooling nozzles on engines with piston cooling. The valve shuts off the oil supply at low engine speeds allowing all the oil to be used for lubricating the engine when starting or running at low idle.
The valve is located in the filter bracket on the cylinder block’s right hand side.
The lubricating oil carries away heat from the engine’s most heated parts and evens out, by its circulation, the temperature differences within the engine. The heat is removed from the lubricating oil in the oil cooler.
On marine engines the engine’s oil cooler is connected to the fresh-water system.
The oil filter is of the full-flow type, which means that all oil is filtered before reaching the bearing points. The oil for the oil cooler (and further to the piston cooling on certain engines) does, however, not pass the filter. The filter is fitted on the right hand side of the cylinder block (industrial engines) or at the front of the engine (marine engines). The filter element consists of folded filter paper.
A relief valve is located in the bracket on the right hand side of the cylinder block. The valve opens and allows the oil to flow past the filter paper should the filter become clogged.
To prevent excess pressure and remove fuel fumes, water vapour and other gaseous combustion products the engine is fitted with a ventilation device, mounted on the rear inspection cover at the valve lifter housing.
On marine engines (later versions) the crankcase gases pass through a replaceable paper filter which separates any oil ;mist before the gases are led out. The filter holder also has a pressure valve which opens if the pressure in the crankcase becomes too high due to a clogged filter. The filter is placed on the right hand side of the engine in connection to the air filter.
Fuel is sucked by the feed pump from the fuel tank and then pumped through the fine filters to the infection pump. Surplus fuel is returned via the relief, located on the injection pump. The injection pump then pumps the amount of fuel, corresponding to the output required, at high pressure through the deliver pipes to the injectors. The injectors atomize the pressurized fuel into the engine’s combustion chambers. Return fuel from the injectors is led back through the fuel leak-off line via the relief valve and return line back to the tank.
The injection pump is located on the left hand side of the engine and is driven from the timing gears. On the TD61 and TID61 models the pump is flange mounted.
The pump is of the piston type and operates with a constant stroke. A control rod rotates the pump plunders during running and thereby controls the amount of fuel injected by the pump. The injection pump is provided with a centrifugal governor.
The injection pump is pressure lubricated by the engine oil system.
The governors are mechanical and work by means of speed-sensitive governor flyweights. The speed is regulated throughout the entire speed range of the engine, from low idling to high idling (variable speed type).
Fuel must be supplied at a certain pressure if the injection pump is to function. This function is performed by the feed pump, which is of the piston type.
The pump shaft eccentric presses down the feed pump plunger by means of the plunger rod. Thus a predetermined quantity of fuel is transferred from the plunger’s suction side via the non-return valve to its deliver side, at the same time as the plunger spring is tensioned.
After the eccentric cam has performed its stroke, the plunger with non-return valve and plunger rod are pressed upwards by the plunger spring. Thus a quantity of fuel is pumped out via the non-return valve in the outlet connection through the filters to the injection pump, at the same time as new fuel is sucked into the plunger’s suction side in the feed pump from the fuel tank.
The valve both limits the feed pressure and provides continuous venting of the fuel system. When the feed pressure is too high the valve opens and fuel passes through the return line back to the tank.
The relief valve is located on the injection pump. This means that the return fuel flushes through the injection pump before it is fed back to the tank. The fuel flow thereby cools the fuel in the pump’s fuel chamber, at the same time equalizing the temperature and thus the viscosity of the fuel. The quantities of fuel delivered to each cylinder is, in this way, more evenly distributed.
Each injector comprises a nozzle holder and a nozzle (jet).
When the fuel pressure reaches the set value (opening pressure) the nozzle needle which is pressed against its seat by a pressure spring lifts and finely atomized fuel is injected into the engine through accurately calibrated holes in the nozzle body.
The tension of the pressure spring, which determines the opening pressure of the injector, is adjusted by means of shims.
The fuel system is fitted with two fuel filters which are connected in parallel and have the same cover. The fuel filters are of the disposable type and the filter element consists of a spiral-wound filter.
The disposable air filter is of the dry type with a filter element of folded paper. Industrial engines are fitted with a pressure drop indicator which shows a red indicator when the filter is clogged and needs replacing.
The engines are water cooled and equipped with a closed cooling system. On marine engines the cooling system is divided into two separate systems, a fresh-water system and a sea water system.
The coolant circulation in the engine (fresh-water system on marine engines) is taken care of by a centrifugal pump driven by the timing gears.
The coolant is pumped by the coolant pump (circulation pump) into a distribution channel in the cylinder blaock and led round the cylinder liners and further up through the cylinder heads.
The coolant is carried from each cylinder head and from the engine’s oil cooler up to the thermostat housing where a thermostat controls the coolant temperature. As long as the coolant is cold the thermostat shuts off the coolant flow to the radiator/heat exchanger. Instead the coolant passes through a by-pass line under the thermostat directly back to the pump’s suction side. When the coolant temperature has reached a certain value, the thermostat opens and releases coolant to the radiator/heat exchanger, at the same time as the by-pass line is closed.
In the radiator/heat exchanger, the heat is transferred from the coolant to the air or sea water before the coolant is sucked into the coolant pump again.
Large quantities of heat are also carried away by the lubricating oil which removes heat via the oil cooler. The lubricating oil is also used on certain engines to remove heat from the pistons.
The cooling system can operate with a certain overpressure, thus reducing the risk of boiling if the temperature gets too high. Should the pressure rise above normal, a pressure valve in the filler cap opens.
The flow through the sea water system (marine engines) is provided by an impeller-type, gear driven pump fitted at the front of engine. The sea water passes through the engine’s heat exchanger, aftercooler and the reverse gear’s oil cooler. For protection from galvanic corrosion, a zinc electrode is built into the reverse gear’s oil cooler.
The engines are fitted with a piston thermostat. Its sensor contains wax. When the engine is cold the thermostat keeps the passage to the radiator/heat exchanger completely closed. Coolant is then fed through a by-pass line directly back to the engine. As the engine gets warm, the wax expands and the thermostat gradually opens the passage to the radiator/heat exchanger at the same time as the by-pass line closes.
The coolant should be a mixture of anti-corrosion additive and water or, if there is a risk of freezing, anti-freeze and water.
The coolant should be changed and the system flushed clean once a year. At the same time check all hoses and connections and cure any leakage. Replace all loose, swollen or otherwise damaged hoses.
All engines are fitted with turbocharger. The turbo units run on floating bearings and consist of an exhaust turbine, bearing housing, and compressor.
By placing a turbine rotor in the exhaust flow and letting it drive a compressor rotor on the inlet side, the inlet air is compressed so that the excess air to the engine increases. This surplus air means that the amount of fuel injected can be increased, at the same times as combustion efficiency is improved. The result is higher output, lower specific fuel consumption and cleaner exhaust gases.
The turbocharger is lubricated and cooled by the engine lubricating oil. The oil is circulated through the outer pipe line connections. On marine engines the turbine housing is fresh-water cooled to reduce heat radiation to the engine room.
TD61AW and TD71AW have turbocharger with wastegate valve (relief valve). Thus a smaller turbocharger can be used. A small turbo gets sufficient amount of exhausts to five a high turbo speed/boost pressure already at low engine speeds, i.e. the engine gets a much improved low speed torque, at the same time as it reacts quicker to load changes. A wastegate valve is fitted to prevent the smaller turbo from overspeeding at high engine speeds. It is controlled by an actuator with a spring-loaded membrane which is affected by the boost pressure through a hose from the compressor housing. The wastegate valve opens at a certain boost pressure and leads part of the exhaust gases past the turbine rotor direct into the exhaust pipe.
The engines are equipped with a 2-pole electrical system with alternator. The system voltage is 24V for industrial engines. As regards marine engines, TAMD61 has 12V (24V as option) and TAMD71 has 24V (12V as option).
All engines are fitted with an electrical pre-heater.
Industrial engines are fitted with one and the marine engines with two semi-automatic fuses of 8A. Industrial engines also have a 5A melt fuse. The fuses are located in the connecter box on the right hand side of the engine (industrial engines) or at the front end of the engine (marine engines). The semi-automatic fuses can be re-set by pressing the button on the fuse. The button is accessible from the outside of the connector box on industrial engines of earlier versions and on marine engines. On later version industrial engines the cover to the connector box must first be removed.
The stop solenoid can either be live when the engine is running or live when the engine is stopped. When stopping the engine, in the first case the current is disconnected and in the second case it is connected. The solenoid is optional equipment for certain industrial engines.