Engine — design features (Renault Sandero 1)

Renault/Dacia Sandero cars are equipped with transversely mounted four-stroke four-cylinder petrol injection engines: 8-valve with a working volume of 1.4 l model K7J and 1.6 l model K7M (both engines are SOHC type), and also the 16-valve 1.6-liter K4M model (DOHC).

Note. The operation of a piston internal combustion engine is based on the use of the work of thermal expansion of heated gases during the movement of the piston from top dead center (TDC) to bottom dead center (BDC). Heating of gases at TDC is achieved as a result of combustion of fuel mixed with air in the cylinder. This increases the temperature of the gases and the pressure. Since the pressure under the piston is equal to atmospheric pressure, and in the cylinder it is much greater, the piston will move downwards under the action of the pressure difference, and the gases will expand, performing useful work. In order for the engine to constantly generate mechanical energy, a mixture of air and fuel must be periodically supplied to the cylinder through the intake valve. The combustion products of the fuel after their expansion are removed from the cylinder through the exhaust valve. These tasks are performed by the valve timing mechanism, which controls the opening and closing of the valves, and the fuel supply system. The working cycle of an engine is a periodically repeating series of sequential processes occurring in each cylinder of the engine and causing the conversion of thermal energy into mechanical work. Automobile engines generally operate on a four-stroke cycle, which is completed in two revolutions of the crankshaft or four strokes of the piston and consists of intake, compression, and expansion strokes (working stroke) and release.

The K7J and K7M engines are almost identical in design, but differ in displacement. Moreover, the displacement of the K7M engine is increased compared to the K7J engine due to the increase in piston stroke, which is achieved by increasing the crankshaft crank radius with the same cylinder diameter. This entailed an increase in the height of the K7M engine cylinder block.

Note: Engine displacement (liter capacity) is one of the most important design parameters (characteristics) internal combustion engine (ICE), expressed in liters (l) or cubic centimeters (cm³).

The engine's working volume largely determines its power and other operating parameters. It is equal to the sum of the working volumes of all engine cylinders. In turn, the working volume of a cylinder is defined as the product of the cross-sectional area of the cylinder and the length of the piston's working stroke (from BDC to TDC). According to this parameter, a distinction is made between long-stroke engines with a piston stroke length exceeding the cylinder diameter, and short-stroke engines with a piston stroke less than the cylinder diameter.

In addition, due to the increased diameter of the clutch, aggregated with the K7M engine, the diameter of the flywheel is also increased, which, in turn, caused a change in the shape of the clutch housing. That is why the location of the threaded holes for fastening the gearbox in the cylinder blocks of these engines is also different. The design of the engines is shown in Fig. 5.1 and 5.2.



The K7J and K7M engines with an overhead camshaft with one five-bearing camshaft have two valves per cylinder. The camshaft of the engines is driven by a reinforced toothed belt. The valves of the K7J and K7M engines are driven from the camshaft by rocker arms, which rest on one shoulder on the camshaft cams and have bolts on the other shoulder for adjusting the clearances in the valve mechanism with locknuts, acting on the ends of the valve stems.

Cylinder head 15 (see fig. 5.1) the engines are made of aluminum alloy with a transverse cylinder scavenging scheme (the inlet and outlet ports are located on opposite sides of the head). The head is pressed with seats and guide bushings 15 (see fig. 5.2) valves. The inlet 7 and outlet 16 valves are each equipped with one spring 14, fixed through a plate 13 by two crackers.





On the upper surface of the K7J and K7M engine block head, the axis 11 of the rocker arms 8 and 12 of the inlet and outlet valves, respectively, is bolted. Bolts 9, secured with locknuts 10, are installed in the holes made in the rocker arms to adjust the clearances in the valve drive mechanism, resting on the ends of the valve stems.

The plane of the joint between the head and the cylinder block is sealed with a gasket, which is a plate molded from thin sheet metal.

Note: Compression ratio is the ratio of the volume of the above-piston space of the cylinder when the piston is at BDC to the volume of the above-piston space of the cylinder when the piston is at TDC, i.e. to the volume of the combustion chamber.

Increasing the compression ratio requires the use of fuel with a higher octane number (for gasoline internal combustion engines) to avoid detonation. Increasing the compression ratio generally increases its power, and also increases the engine efficiency, i.e. helps reduce fuel consumption.

In the 1950s and 1960s, one of the trends in engine building was to increase the compression ratio, which by the early 1970s often reached 11-13:1. However, this required the appropriate gasoline with a high octane number, which in those years could only be obtained by adding poisonous tetraethyl lead (leaded gasoline). The introduction of environmental standards in most countries in the early 1970s led to a halt in the growth and even a reduction in the compression ratio in production engines.



The term "compression ratio" should not be confused with the term "compression", which means (at a certain structurally determined degree of compression) maximum pressure created in the cylinder when the piston moves from BDC to TDC (for example, compression ratio is 10:1, compression is 14 atm).

Camshaft engines 14 (see fig. 5.1) installed in bearing beds made in the head body and fixed against axial movement by thrust flanges.

Cylinder blocks 16 (see Fig. 5. The engines being added are identical and are a single casting that forms the cylinders, cooling jacket, upper part of the crankcase and five crankshaft supports made in the form of crankcase partitions. The cylinder block is made of special high-strength cast iron with cylinders bored directly in the block body. The 2 main bearing caps are machined together with the block and are not interchangeable. The cylinder block has special bosses, flanges and holes for fastening parts, units and assemblies, as well as channels for the main oil line.

Crankshaft 1 rotates in main bearings having thin-walled steel liners 20 and 21 with an antifriction layer. The axial movement of the crankshaft is limited by two thrust half rings installed in the grooves of the bed of the middle main bearing.

Flywheel 17, cast from cast iron, is installed on the rear end of the crankshaft and secured with seven bolts. A toothed rim for starting the engine with a starter is pressed onto the flywheel. In addition to it, a toothed crown is made on the flywheel, ensuring the operation of the top dead center sensor of the engine management system.



Pistons (Fig. 5.3) are made of aluminum alloy. On the cylindrical surface of the piston head there are annular grooves for the oil scraper and two compression rings.

Piston pins 3 (see fig. 5.2) they are installed in the piston bosses with a gap and are pressed with tension into the upper heads of the connecting rods, which are connected with their lower heads to the connecting rod journals of the crankshaft through thin-walled liners, similar in design to the main ones.

Connecting rods2 steel, forged, with I-section rod.

Lubrication system combined (for more details see. "Lubrication system").

Crankcase ventilation system closed type does not communicate directly with the atmosphere, therefore, simultaneously with the suction of gases in the crankcase, a vacuum is formed in all engine operating modes, which increases the reliability of various engine seals and reduces the emission of toxic substances into the atmosphere.

The system consists of two branches, large and small.

When the engine is idling and operating at low loads, when the vacuum in the intake manifold is high, crankcase gases are sucked in by the intake manifold through the small branch of the system.

At full load conditions, when the throttle valve is open at a large angle, the vacuum in the intake pipe decreases, and in the air supply hose it increases, and crankcase gases through the large branch hose connected to the fitting on the cylinder head cover mainly enter the air supply hose, and then through the throttle assembly into the intake pipe and engine cylinders.



Cooling system engines, hermetically sealed, with an expansion tank, consists of a cooling jacket made in casting and surrounding the cylinders in the block, combustion chambers and gas channels in the cylinder head. Forced circulation of the coolant is provided by a centrifugal water pump 7 (see fig. 5.1) with a crankshaft drive by a toothed timing belt. To maintain the normal operating temperature of the coolant, a thermostat is installed in the cooling system, which closes the large circle of the system when the engine is not warmed up and the coolant temperature is low.

Power supply system engines consists of an electric fuel pump installed in the fuel tank, a throttle assembly, a fine fuel filter, a fuel pressure regulator located in the fuel pump module, injectors and fuel lines, and also includes an air filter.

Ignition system engines microprocessor, consists of an ignition module, high-voltage wires and spark plugs. The ignition module is controlled by an electronic unit of the engine management system. The ignition system does not require maintenance or adjustment during operation.

The main difference between the K4M engine (Fig. 5.4) and the K7J and K7M engines is the presence of a cylinder head with two camshafts (separate intake and exhaust valves).

The camshafts are driven by a reinforced toothed belt. Sixteen valves of the K4M engine are driven by camshafts using roller rocker arms (rockers) and hydraulic tappets. The hydraulic tappets automatically ensure gap-free contact of the camshaft cam with the valve. The cylinder block, crankshaft, flywheel, pistons, piston pins, connecting rods of the K4M and K7M engines are identical. The lubrication, cooling, and power supply systems are also similar in design.



Each cylinder of the K4M engine is equipped with four ignition coils, which are directly controlled by the electronic control unit (ECU) of the engine. Moreover, there are no high-voltage wires, and the ignition coils are mounted directly on the spark plugs.

Power unit (engine with gearbox, clutch and final drive) mounted on three supports with elastic rubber elements: two upper side (right and left), bearing the main mass of the power unit, and the rear, compensating for the torque from the transmission and the loads that arise when the car starts moving, accelerates and brakes.

Helpful tips:

• With a certain amount of skill and attentiveness, many engine and system faults can be determined quite accurately by the color of the smoke coming out of the exhaust pipe. Blue smoke indicates that oil is getting into the combustion chambers, and constant smoking is a sign of severe wear of the cylinder-piston group parts. The appearance of smoke during revving, after prolonged cranking by the starter, after long idling or immediately after engine braking usually indicates wear of the valve stem seals. Black smoke is a sign of too rich a mixture due to a faulty engine management system or injectors. Gray or thick white smoke with an admixture of moisture (especially after the engine overheats) means that the coolant has burst into the combustion chamber through a damaged cylinder head gasket. If this gasket is severely damaged, the liquid sometimes gets into the oil pan, the oil level rises sharply, and the oil itself turns into a cloudy whitish emulsion. White smoke (steam) with an unheated engine in damp or cold weather is normal.
• Quite often you can see a car standing in the middle of a city traffic jam with the hood open, emitting clouds of steam. Overheating. Of course, it is better not to allow this, looking at the temperature gauge more often. But no one is insured against the fact that the thermostat, electric fan may suddenly fail, or the coolant may simply leak. If you missed the moment of overheating, do not panic and do not aggravate the situation. Overheating is not as scary as its possible consequences. Never turn off the engine immediately - it will get a heat stroke and, perhaps, after cooling down, will refuse to start at all. After stopping, let it run at idle speed, while the circulation of liquid in the system will remain. Turn on the heater to maximum power and open the hood. If possible, pour cold water on the radiator. Only after achieving a decrease in temperature, stop the engine. But never immediately open the cap of the expansion tank: on an overheated engine, a geyser from under the open cap is guaranteed. Take your time, let everything cool down, and you will preserve the health of the car and your own health. Almost all car manuals recommend that you always depress the clutch when starting the engine. This recommendation is justified only in the case of starting in severe frost, so as not to waste battery energy on turning the shafts and gears of the gearbox in thickened oil. In other cases, this measure is aimed only at preventing the car from moving if a gear is engaged due to forgetfulness. Such a technique is harmful to the engine, since significant force is transmitted to the crankshaft thrust bearing through the squeezed clutch, and when starting (especially cold) lubrication does not reach it for a long time. The bearing wears out quickly, the crankshaft gets axial play, and starting from a standstill begins to be accompanied by strong vibration. In order not to damage the engine, get into the habit of checking the position of the gearshift lever before starting and starting the engine with the parking brake on, without squeezing the clutch unless absolutely necessary.

Possible engine malfunctions, their causes and solutions

Cause of malfunction	Method of elimination
The engine won't start
No fuel pressure in the rail:
fuel lines are clogged	Flush and blow out the fuel tank and fuel lines
the fuel pump is faulty	Replace the pump
the fuel filter is clogged	Replace the filter
the fuel pressure regulator is faulty	Check the regulator, replace the faulty one
The ignition system pump is faulty	Cm. "Engine management system"
Engine runs rough or stalls at idle
Insufficient pressure in the fuel rail	See the fault "Engine does not start"
The idle speed control valve is faulty	Replace the idle air control valve
The throttle position sensor is faulty or the throttle assembly is dirty	Replace the sensor or clean the throttle valve
Air leakage through the engine crankcase ventilation hoses and the hose connecting the intake pipe to the brake booster	Tighten the mounting clamps, replace damaged hoses
The ignition system is faulty	Cm. "Engine management system"
The variable valve timing system is faulty	Contact the service for diagnostics and repair of the system
The engine does not develop full power and is not responsive enough
Incomplete throttle opening	Adjust the throttle actuator
Throttle position sensor is faulty	Replace the sensor
Insufficient pressure in the fuel rail	See the fault "Engine does not start"
The air filter is dirty	Replace the filter element
The ignition system is faulty	Cm. "Engine management system"
Clearances in the valve drive mechanism of K7J and K7M engines are damaged	Adjust the valve clearances
Wear of hydraulic valve compensators of the K4M engine	Replace hydraulic lifters
Insufficient compression - below 1 MPa (10 kgf/cm²):
the cylinder head gasket is blown	Replace the gasket
burnt pistons, broken or stuck piston rings	Clean the rings and piston grooves from carbon deposits, replace damaged rings and pistons
poor valve seating	Replace damaged valves, polish seats
excessive wear of cylinders and piston rings	Replace pistons, bore and hone cylinders
The variable valve timing system is faulty	Contact the service for diagnostics and repair of the system
Insufficient oil pressure in a warm engine
Using the wrong grade of oil	Replace the oil with the recommended one
Dilution or foaming of oil due to penetration of fuel or coolant into the oil pan	Eliminate causes of fuel or coolant leakage, change oil
Contamination of the working cavity or wear of the oil pump parts	Flush or replace the oil pump
Clogged oil filter	Replace the oil filter
Excessive reduction in clearance between the oil receiver and the bottom of the oil pan or damage to the oil receiver caused by impact with a road obstacle	Straighten the deformed oil pan, replace the damaged oil receiver if necessary
Increased clearance between main and connecting rod bearing shells and crankshaft journals	Grind the journals and replace the bearings
Cracks, pores in the walls of the cylinder block oil channels or clogged oil lines	Repair the cylinder block. If the defect cannot be eliminated, replace the block.

Cause of malfunction	Method of elimination
Knocking of crankshaft main bearings
Usually a dull, metallic knock. It is detected when the throttle valve is opened sharply at idle. Its frequency increases with increasing crankshaft speed. Excessive axial clearance of the crankshaft causes a sharper knock, with uneven intervals, especially noticeable with a smooth increase or decrease in crankshaft speed.
Insufficient oil pressure	See fault "Insufficient oil pressure in warm engine"
The flywheel mounting bolts are loose	Tighten the bolts to the recommended torque
Increased clearance between journals and main bearing shells	Grind the journals and replace the bearings
Increased clearance in the crankshaft thrust bearing	Replace the center main bearing shells, check the clearance
Knocking of connecting rod bearings
Usually the knock of connecting rod bearings is sharper than the knock of main bearings. It can be heard at idle speed when the throttle valve is opened sharply. The place of knocking can be easily determined by disconnecting the spark plugs one by one (ignition coils on the K4M engine).
Insufficient oil pressure	See the fault "Insufficient oil pressure in a warm engine".
Excessive clearance between the crankshaft journals and the bearings	Replace the bearings and grind the journals
Knocking of pistons
The knock is usually soft, muffled, and is caused by the piston "beating" in the cylinder. It is best heard at low crankshaft speeds and under load.
Increased clearance between pistons and cylinders	Replace pistons, bore and hone cylinders
Excessive clearance between piston rings and piston grooves	Replace rings or pistons with rings
Increased noise from the valve timing mechanism
Low oil pressure in the lubrication system	See fault "Insufficient oil pressure on warm engine"
Increased clearances in the valve drive mechanism of K7J and K7M engines	Adjust the valve clearances
Wear of hydraulic valve compensators of the K4M engine	Replace hydraulic lifters
Valve spring failure	Replace the spring
Excessive clearance between the valve stem and the guide bushing caused by wear	Replace the valve and guide bushing
Camshaft cam wear	Replace the camshaft
A knock on a cold engine, audible for two to three minutes after starting and increasing in intensity as the crankshaft speed increases
Increased clearance between pistons and cylinders	Piston knocking that disappears after the engine warms up is not a sign of a malfunction. If the knocking is constant, replace the pistons, bore and hone the cylinders
Loose crankshaft pulley fastening	Tighten the fastening
Brief knocking sounds immediately after starting the engine
Using the wrong grade of oil (with reduced viscosity)	Replace the oil with the one recommended by the vehicle manufacturer
Increased crankshaft axial clearance	Replace the thrust half rings of the middle main bearing
Increased clearance in the front main bearing	Replace the main bearing shells
Knocking noises on a warm engine in idle mode
Loose or worn accessory drive belt	Adjust the belt tension or replace it
Noise from the valve timing mechanism parts	See fault "Increased noise of the valve timing mechanism"
Using the wrong grade of oil	Replace the oil with the one recommended by the vehicle manufacturer
Increased clearances between piston pins and piston boss holes	Replace pistons and pins
Increased clearances between the crankshaft journals and the bearings	Replace the bearings and grind the journals
The axes of the upper and lower connecting rod heads are not parallel	Replace the connecting rod

Cause of malfunction	Method of elimination
Loud knocking in a warm engine when the crankshaft speed increases
Crankshaft pulley hub failure	Replace damaged parts
Excessive tension of the accessory drive belt or the appearance of cracks and breaks on it	Adjust the belt tension, replace the damaged belt
The flywheel mount is loose	Tighten the flywheel mounting bolts to the specified torque
Excessive increase in clearances between the connecting rod and main bearing shells of the crankshaft	Regrind the journals to the repair size and replace the liners
Increased engine vibration
Crankshaft imbalance	Remove and balance the crankshaft
Pistons of different weights are installed	Disassemble the connecting rod and piston group, select pistons by weight
Unequal clearances in the valve drive mechanism of K7J and K7M engines	Adjust the valve clearances
Wear of hydraulic valve compensators of the K4M engine	Replace hydraulic lifters
Uneven compression values in cylinders	cm. "Checking the compression in the cylinders"
The powertrain suspension mounts are badly worn or hardened	Replace the supports
Engine detonation knocks
Using low octane gasoline	Fill with gasoline of the appropriate octane rating
The electronic engine control unit is faulty	Replace the block
The knock sensor is faulty	Replace the sensor
Increased oil consumption
Oil leaking through engine seals	Tighten the fasteners or replace the gaskets and seals
The crankcase ventilation system is clogged	Flush the crankcase ventilation system components
Wear of piston rings or engine cylinders	Rebore cylinders, replace pistons and rings

Cause of malfunction	Method of elimination
Broken piston rings	Replace the rings
Coking of oil scraper rings or grooves in piston grooves due to the use of non-recommended oil	Clean the rings and grooves from carbon deposits, replace the engine oil with the recommended one
Worn or damaged valve stem seals	Replace the valve stem seals
Increased wear of valve stems or guide bushings	Replace valves, repair cylinder head
Engine overheating
Insufficient amount of fluid in the cooling system	Add coolant to the cooling system
The outer surface of the radiator is heavily contaminated	Clean the outer surface of the radiator with a jet of water
Thermostat is faulty	Replace Thermostat
The electric fan of the cooling system is faulty	Check the fan motor and its relay, replace faulty components
The expansion tank cap valve is faulty (is constantly open, which is why the system is under atmospheric pressure)	Replace the expansion tank cap
Using low octane gasoline	Fill with gasoline of the appropriate octane rating
Rapid drop in fluid level in expansion tank	Rapid drop in fluid level in expansion tank
The radiator is damaged	Repair or replace the radiator
Damage to hoses or gaskets in pipeline connections, loose clamps	Replace damaged hoses or gaskets, tighten hose clamps
Fluid leaking through water pump seal	Replace the water pump
The cylinder head gasket is damaged	Replace the gasket
Fluid leakage through microcracks in the block or cylinder head	Check the tightness of the block and cylinder head; if cracks are found, replace damaged parts