The block and cylinder head do not require maintenance, except for cleaning from dust and dirt and tightening threaded connections

Over time, the cylinder head gasket is crumpled, so loosening of the head fastening nuts, burning of the gasket and breakthrough of gases to the outside is possible, therefore, during operation, every 20,000 km of the car’s run, it is necessary to tighten the cylinder head.

The cylinder head stud nuts are tightened from the middle of the head to the ends (front and rear).

Cylinder head nut tightening sequence

Tightening and checking torques should be done on a cold engine.

If this operation is performed on a hot engine, then after it cools down, the tightening of the nuts will be incomplete due to the large difference in the coefficients of linear expansion of the material of the head, block and studs.

For a uniform and tight fit of the head to the block, tightening should be done in two steps: first - with a small effort and finally - with a specified torque of 83-90 Nm (83-9.0 kgcm).

Rock cover bolt tightening sequence

It should be borne in mind that tightening the nuts causes a change in the gaps in the gas distribution mechanism. Therefore, after each such operation, it is necessary to check the gaps between the rocker arms and valve stems.

If necessary, the thermal clearances must be adjusted. to ensure a tight and uniform fit of the rocker cover gasket to the cylinder head, tighten the rocker cover bolts in the sequence shown in the figure.

During the operation of the engine, especially a worn one, the rings of which pass a lot of oil, a layer of soot is deposited on the walls of the combustion chamber and the bottoms of the pistons.

Deposit impairs heat transfer through the walls into the coolant, resulting in local overheating, detonation and glow ignition phenomena, engine power decreases, and fuel consumption increases.

When such signs appear, remove the head and clean the combustion chamber and piston crown from carbon deposits.

Before cleaning, soot should be moistened with kerosene. This prevents soot from spraying and prevents poisonous dust from entering the respiratory tract.

Deposit is also formed during long-term operation at low loads of a serviceable, unworn engine.

In this case, the carbon burns out during prolonged movement at high speed.

When removing the cylinder head, it is recommended to grind the valves.

During operation, every 20,000 km of the cars run, it is necessary to check and adjust the clearance between the valves and rocker arms. this should be done on a cold engine (+20 ° C) with tightened nuts for fastening the cylinder head and nuts for fastening the racks of the rocker axis.

The thermal gap between rocker arms and valves should be within 035-045 mm.

With increased clearances, valve knocking occurs, and with reduced clearances, the valve may not fit snugly to the seat and the valve will burn out, therefore, the above clearance values ​​u200bu200bshould not be reduced even if there is some knocking, which, although unpleasant to the ear, does not cause disruption of normal operation engine.

It is recommended to check and adjust thermal gaps in the following sequence:

  • - set the piston of the 1st cylinder to the TDC of the compression stroke. to do this, turning the crankshaft with a special key, combine the third mark on the damper part of the crankshaft pulley with the pointer rib on the timing gear cover.

During the compression stroke, both rocker arms of the 1st cylinder should swing freely on the axles, i.e. both valves are closed.

Check the gap between the rocker arm and the valve with a feeler gauge.

If the gap is incorrect, unscrew the nut of the adjusting screw with a wrench and, turning the adjusting screw with a screwdriver, set the gap using the feeler gauge.

Supporting the adjusting screw with a screwdriver, lock it with a nut and check the clearance is correct;

  • - turn the crankshaft half a turn, adjust the clearances for the 2nd cylinder;
  • - turn the crankshaft another half turn, adjust the clearances for the 4th cylinder;
  • - turn the crankshaft another half turn, adjust the clearances for the 3rd cylinder.

During the operation of the car, the oil level in the crankcase and the tightness of the lubrication system should be checked daily.

After every 10,000 km of the cars run, the oil in the lubrication system and the oil filter element should be changed in a timely manner flush the lubrication system and eliminate leaks that appear in the joints of parts.

The oil level is checked with the engine off by the marks on the pointer rod.

It is recommended to keep the oil level near the "P" mark.

Increasing the level above the “P” mark is undesirable, as the crank heads of the connecting rods will be immersed in oil and spray it, causing excessive oil mist to form in the crankcase.

This causes splashing of spark plugs, intense carbon deposits on the piston crowns and combustion chamber walls, ring coking, engine smoke and increased oil consumption.

Lowering the oil level below the min mark is dangerous, as this stops the oil supply to the system and the bearings may melt.

The oil level should be checked a few minutes after filling or stopping the engine.

After changing the oil, start the engine and let it run for a few minutes.

After a while, check the oil level as above.

Drain oil for replacement only when the engine is hot. In this case, the oil has a lower viscosity and flows well.

When changing the oil, you should also drain the sediment from the oil filter, clean the inside of the housing and the rod, and change the filter element.

The filter element must be impregnated with clean engine oil before installation. to ensure a snug fit of the filter cover, it is recommended to put it together with the gasket in the same position as it occupied before removal.

Do not overtighten the cover bolt, as this may cause deformation of the cover.

The tightness of the cover is checked after starting the engine.

To prevent unfiltered oil from entering the engine, the rubber o-rings of the filter element must be resilient and not deformed.

When transferring engine operation to another brand of oil, it is necessary to flush the lubrication system with fresh oil of the brand that will be used to lubricate the engine.

To do this, it is necessary to drain the old oil from the crankcase of a warm engine, fill in flushing oil 2-4 mm above the min mark on the oil level indicator, start the engine and run for 15 minutes.

In idling mode at low speed, stop the engine, drain the oil from the crankcase, replace the filter element and fill in fresh oil.

During operation, top up the oil only of the brand that is filled in the engine.

To service the crankcase ventilation system, you must:

  • - remove the air filter, crankcase ventilation hoses;
  • - remove rocker cover and carburetor;
  • - rinse with kerosene and blow air through the rocker cover and hoses;

Scheme of carburetors K-151, K-151d

  • - clean the calibrated hole 50 in the body of the mixing chambers with a copper wire with a diameter of 1.5 mm;
  • - ensure the tightness of all connections during assembly.

During operation, work should not be allowed with an open oil filler neck: this leads to unclean air entering the engine and causes increased wear of engine parts.

To check the correct assembly and normal operation of the crankcase ventilation system, it is necessary to pinch the hose that supplies crankcase gases to the carburetor with the engine running at minimum idle speed.

If the engine speed drops sharply or the engine stalls, the system is working properly.

Care of the cooling system - consists in daily checking the coolant level in the expansion tank.

The fluid level on a cold engine must be at least the MIN mark.

The MIN mark is on the side of the expansion tank.

If necessary, add coolant to the expansion tank. In cases of frequent topping up, check the tightness of the cooling system.

When servicing the cooling system, it should be borne in mind that the coolants "Tosol-A 40M", Lena, Thermosol are poisonous and flammable, as they contain ethylene glycol in their composition.

By analogy with the latter, liquids have a poisonous and narcotic effect and the ability to penetrate the body through the skin.

When it enters the body through the mouth, the coolant causes chronic poisoning with damage to the vital organs of a person (affects blood vessels, kidneys, nervous system).

Therefore, the following precautions must be observed when using coolant:

  • —do not suck liquid with your mouth when transfusing it;
  • —do not smoke or eat while working with coolant;
  • - in cases where splashing of coolant is possible during operation, use safety glasses;
  • - open Clean areas of skin that have come into contact with coolant should be washed with soap and water.

After every 10,000 km, it is necessary to adjust the tension of the auxiliary drive belts, as well as check the tightness of all connections in the cooling system.

If drops or slight moisture are detected, the clamps of the connections should be tightened.

In case of significant leaks of liquid, the use of water is allowed in exceptional cases to restore the level.

However, this will inevitably reduce the density of the mixture and increase its freezing point. Therefore, at the first opportunity, the mixture should be replaced with a new coolant.

When adding water to the cooling system, the level in the expansion tank should be 7-10 cm above the MIN mark.

Before starting winter operation, check the density of the liquid in the cooling system, which should be in the range of 1078-1085 g / cm3 at 20 ° C.

After every three years, it is necessary to flush the cooling system and fill in new coolant, and it is also recommended to check the operation of the thermostat and the expansion tank plug valve block.

Replace the coolant in the following order:

  • - place the car on a horizontal platform;
  • - make sure that the heater tap is open, for which turn on the ignition, turn the knob 4 of the air temperature regulator, turn off the ignition;
  • - remove the plug of the expansion tank;

Heater radiator connection diagram with tap and electric pump

  • — drain the coolant from the engine and radiator through tap 1 and plug 13;
  • - disconnect the drain hose of the heating system from the fitting on the engine (on the right side) and the supply hose from the lower pipe of the heater radiator;
  • - on GAZ-2705 "Combi" cars and on buses, remove the protective cover of the heater hoses on the floor in the cab and disconnect the hoses from the radiator 4 of the additional heater, having previously installed a liquid container under the lower radiator tube;
  • - after draining the liquid from the heating system, install the removed hoses in their places.

Rinse the cooling system, for which:

  • - turn on tap 1 and radiator cap 13;
  • - fill the engine cooling system with clean water through the filler neck of the expansion tank to a normal level and tighten the tank cap;
  • - start the engine, warm it up at medium speed to 80-90 ° C and run for 3-5 minutes;
  • -stop the engine and drain the water as above.

Fill the cooling system, for which:

  • - turn on the cock on the engine block and the radiator cap. The plug of the tee 8 (see) must be turned out 2-3 turns;
  • - slowly pour liquid into the expansion tank. If the liquid does not leave the tank, then vigorously press the radiator outlet hose 1-2 times to remove accumulated air;
  • - when liquid appears from under the plug of the tee, wrap the plug.

After refueling, start the engine and, idling, warm it up until the main thermostat valve opens. At the same time, it is necessary to turn on the electric pump on GAZ-2705 Combi cars and on buses.

Let the engine run for 3-5 minutes. (cycles) at different speeds of the crankshaft: 3000 min1 - 0.5 min.; 1500 min1 - 0.5 min; minimum idle speed - 0.5 min.

Check the cooling system for leaks. After the engine has cooled down, check the fluid level in the expansion tank and top up if necessary.

Checking the operation of the thermostat consists in checking the temperature at which the main valve opens, the value and time of its full opening.

To do this, the thermostat is removed from the engine and placed in a tank with a coolant with a volume of at least 3 liters and fixed on the bracket so that the entire thermal force element is washed by the flows of the agitated liquid.

The intensity of liquid heating after 55°C should be no higher than 1°C per minute.

The temperature at which the valve stroke is 0.1 mm is taken as the temperature at which the main valve opens. This temperature should be 80°C.

At a temperature that is 15°C higher than the temperature at which the main valve opens, the full opening of the valve must be at least 8.5 mm.

The time of full opening of the main valve is determined from the moment the thermoforce element is immersed in liquid at a temperature of about 100 ° C. This time should not exceed 80 s.

During operation, the following parameter deviations are allowed thermostat values ​​relative to nominal values:

  • temperature of the beginning of opening of the main valve - by 3 ° С;
  • Loss of valve travel by 20%.

The simplest thermostat test can be done by touch directly on the car.

After starting a cold engine with a working thermostat, the hose connecting the thermostat pipe to the right (in the direction of the car) radiator tank should heat up when the coolant temperature reaches 80-90 ° C.

In this case, the arrow of the coolant temperature gauge should be set on the green zone of the instrument scale.

It is necessary to maintain the correct tension of the accessory drive belts.

The deflection of the fan drive belt should be within 7-9 mm, the deflection of the drive belt for the coolant pump and the generator should be within 8-10 mm with a load of 40 N (4 kgf) on each of them.

Check with a dynamometer 7870-8679 as follows:

Dynamometer 7870-8679 for checking tension of accessory drive belts

  • - install the dynamometer with bar 5 alternately on the pulleys of the fan and tension roller, coolant pump and generator;
  • - press the handle 1 with your hand until the collar 3 touches the rod with the bushing 4 and determine the belt tension force on the scale 2;

Accessory Drive Belts

  • - if necessary, adjust the tension of the fan drive belt by changing the position of the tension roller 2 (see), the generator drive belt and the coolant pump - by changing the position of the generator.

If the belt tension is too low, the belts slip, which leads to defective operation of the fan, coolant pump and alternator, as well as to strong heating and delamination of the belts.

Over-tensioning the belts causes rapid wear on the fan bearing, coolant pump, alternator and idler pulley, as well as pulling and breaking the belts themselves.

Caring for the power system. A prerequisite for the reliable operation of the power supply system is the cleanliness of its devices and components.

It is necessary to pour only clean gasoline into the tank, and periodically drain the sediment and water from the tank.

It is necessary to carefully check the tightness of the connections of the fuel lines and other components of the system in good light, at an engine speed corresponding to idling.

Fuel leaking creates a fire hazard. Leaky connections are eliminated by tightening nuts, fittings and clamps.

Caring for the throttle and air damper drive consists in replacing parts that have failed.

Throttle and choke actuator

The installation of the throttle actuator (see) must be carried out as follows:

  • - install the tips with glands 5 and 18 in the front panel of the cab and the bracket 7 of the carburetor;
  • —pass the cable through the holes of the tips 5 and 18 from the cabin side;
  • —insert the ends of the inner tube of the shell 3 into the sockets of the tips 5 and 18, and put the ends of the outer tube on the ends of the tips;
  • - put the end of the cable with a tip into the socket of the coupling 6 and fasten it with a pin with a cotter pin on the pedal lever with the slot up;
  • — keeping pedal 11 pressed against the floor mat, and sector 13 in the fully open throttle position, fasten cable 16 to sector 13 using bracket 12;
  • - if necessary, adjust the cable tension as accurately as possible by moving the tip 18 in the bracket 1 and using the nuts 17 (to ensure full opening and closing of the throttle valves);
  • - having completed the adjustment, set sector 13 to the position of fully closed throttle valves (pedal in the upper position) and fix the lever limiter 8 in the position of contact with the bracket 9.

When installing a flexible rod, avoid sharp bends in the cable, since if there is a bend in the cable, it may jam in the sheath, as well as premature breakage of the cable and wear of plastic tubes.

Care of the air filter consists in the periodic replacement of the filter element.

To do this, unfasten five latches and remove the filter cover.

When assembling the filter, it is necessary to pay attention to the correct location of the seals between the filter housing and the filter element, the filter cover, and as well as connecting the body to the carburetor.

When repairing the filter, the failed parts are replaced.

Caring for the fuel filter-sump consists in periodically draining the sludge (every 20,000 km) through the drain plug, washing the filter housing and its filter element seasonally, once a year.

Fuel sediment filter

To remove the filter element, it is necessary to unscrew the two bolts securing the bracket 8 (see) of the sump to the frame, unscrew the bolts 1, remove the housing with the bracket 8, remove the washer 12 and the spring 11.

Rinse the filter element and filter housing with clean unleaded gasoline.

When assembling the sediment filter, it is necessary to monitor the correct installation of gaskets 2 and 6.

Caring for the fine fuel filter consists in periodically cleaning the sump from dirt and sediment after 20,000 km, washing the mesh filter element or replacing the paper filter element (for engines manufactured before 2001), replacing the filter assembly (for engines release since 2001).

Care of the fuel pump consists in periodically removing dirt from the head and washing the strainer.

There are two ways to check the pressure developed by the pump.

First way

The check is carried out directly on the car with the engine running at the minimum stable speed.

The fuel pump is disconnected from the carburetor (the engine is powered by gravity) and connected to a pressure gauge with a scale of up to 100 kPa (1 kgf / cm2).

For a serviceable pump, the pressure should be within 23-32 kPa (023-032 kgf/cm2).

You can check the pump pressure, but less accurately, without disconnecting it from the carburetor, but by connecting a pressure gauge through a tee screwed in at the fuel outlet of the pump.

After checking the pressure, stop the engine. Pressure readings on the pressure gauge scale must be maintained for at least 10 seconds.

A faster pressure drop indicates a pump failure.

Fuel pump tester schematic

Second method

  • The pump is checked on a special device, which must provide a suction and discharge height of 500 mm.
    When checking on this device, the fuel pump must meet the following requirements: at a camshaft speed of the device 120 minˉ¹the pump must provide:
    - zero flow pressure 23—32 kPa (023—032 kgf/cm2);
  • - the minimum vacuum in the suction line is not less than 48.5 kPa (365 mm Hg). the pressure and vacuum created by the pump must be maintained with the drive turned off for at least 10 seconds;
  • —pump flow rate at 1800 min1 of the camshaft of the device must be at least 145 l/h.

Carburetor care includes:

  • - inspection and removal of dust and dirt and checking the tightness of all connections, plugs and plugs;
  • - checking and adjusting the fuel level in the float chamber;
  • - checking the adjustment of the idle system;
  • - cleaning and flushing the channels and dosing elements of the carburetor.

Float adjustment

The fuel level in the float chamber is checked once a year with the vehicle on level ground, with the engine off and the carburetor cap removed.

The fuel level must be within the size ((A)) (20-23 mm from the plane of the float chamber connector).

The level is adjusted by bending the tongue 4 of the float lever 1. In this case, the float must be in a horizontal position, and the stroke of valve 3 must be 20-2.3 mm.

The stroke of the valve is adjusted by bending the tongue 2 of the drive lever.

When adjusting the float mechanism, care must be taken not to damage the sealing washer 5.

If the adjustment does not give the desired result, it is necessary to check the carburetor float mechanism.

Typically, high or low fuel levels in the float chamber are caused by a leaky float, an incorrect weight, or a leaky fuel valve.

The tightness of the float is checked by immersing it in hot water with a temperature of at least 80 ° C and a holding time of at least half a minute.

If the float is leaking, as indicated by the release of air bubbles, the float must be soldered, after removing gasoline from it.

After soldering, it is necessary to check its tightness and weight again. Weight the float assembly with the lever should be no more than 12.5 g.

If the fuel valve is leaking, replace sealing washer 5.

After checking and troubleshooting the float mechanism, check the fuel level in the float chamber again and, if necessary, adjust it as described above.

The adjustment of the minimum speed of the engine crankshaft, the content of carbon monoxide (CO) and hydrocarbons (CH) in the exhaust gases at idle is carried out according to the method of GOST at special posts in car fleets or at car service stations ( STO).

The content of CO and CH in the exhaust gases should not exceed:

  • - 3.5% CO and 1200 ppm—1 CH at minimum idle speed
    - 20% CO and 600 ppm—1 CH at increased idle speed

The check should be carried out with the engine warmed up to a coolant temperature of 80-90 ° C, and with the carburetor air damper fully open.

The order of checking is as follows:

  • - let the engine run for 15 seconds. at an increased crankshaft speed;
  • - reduce the crankshaft speed to the minimum idle speed;
  • - after 20 sec. at the established minimum crankshaft speed, check the content of CO and CH in the exhaust gases.

Sudden transitions from one mode to another are not allowed.

Before adjusting, it is necessary to make sure that the ignition system is working, paying special attention to the condition of the spark plugs and the correct gaps between the electrodes, as well as for the ZMZ-4025, ZMZ-4026 and UMP engines, check and, if necessary, adjust the ignition timing at the minimum frequency idle speed and gaps between the rocker arms and valves of the gas distribution mechanism.

The adjustment is made on the engine, warmed up to a coolant temperature of 80-90 ° C.

The order of adjustment is as follows:

Carburetor Adjustment Screws

  • - remove the restrictive cap from screw 2 of the mixture composition (quality screw).
  • - turn screw 2 and screw 3 for operational adjustment of the idle speed (quantity screw) to the stop, but not too tight, then unscrew screw 3 by 5-6 turns, and screw 2 by 2-3 turns.
  • - start the engine and use screw 3 to set the crankshaft speed (60050)min1
  • - adjust the content of carbon monoxide and hydrocarbons in the exhaust gases by screwing in screw 2 and maintaining the specified speed with screw 3, to achieve stable engine operation.

In order to ensure optimal engine operation, the plant recommends setting the CO content within 0.5 h 15% and the CH content - no more than 800 ppm—1.

  • - increase the engine speed to (270050) min1 and check the content of carbon monoxide and hydrocarbons. In accordance with GOST, it should not exceed 2% and 600 ppm—1, respectively.

Exceeding the limits indicates a malfunction of the carburetor.

  • - to check the correctness of the adjustment, press the accelerator pedal and release it sharply.

If the engine stalls, then by slightly unscrewing the screw 3, increase the crankshaft speed, but not more than (60050)min-1.

  • - after the end of the adjustment, put a restrictive cap on screw 2.

Its color should be different from the color of the cap installed by the manufacturer.

During operation, screws 2 and 3 can only be used to adjust the factory settings to obtain the most stable engine operation at the minimum idle speed.

In this case, screwing in screw 2 is allowed only at an angle limited by moving the flag of the restrictive cap from stop to stop (approximately 270 °).

Attempting to rotate the restrictor cap to a greater angle will cause it to break.

Cleaning and flushing of the carburetor must be carried out on a clean, specially equipped workbench. to perform these works, the carburetor must be completely disassembled, then thoroughly rinse the outer and inner surfaces of the cover, carburetor body, diffusers, throttle body, clean of resinous deposits and rinse the fuel, air and emulsion jets, as well as the channels in the carburetor body.

Use unleaded gasoline for flushing.

The carburetor and its parts must be blown out with compressed air after washing.

Flushing the carburetor with solvents and wiping the parts with a wipe other ends are not allowed.

It is strictly forbidden to clean the calibrated holes with metal objects.

When disassembling and assembling, it is necessary to use only serviceable tools in order to avoid breaking the splines and crushing the nuts.

Tightening the carburetor fasteners should be done evenly, avoiding warping of the flanges.

Caring for the recirculation system consists in cleaning the holes in the intake pipe with a wire with a diameter of 4 mm and blowing them out with the recirculation valve removed after 60,000 km of the car.

Caring for the exhaust system consists in periodically tightening all fasteners, especially the muffler, resonator and exhaust pipe connections. The failed muffler, resonator and mounting parts are replaced with new ones.

Care of the engine mount consists in periodic (every 20,000 km) checking of its condition, tightening the brackets and rubber pads.

To increase the durability of the pillows, it is necessary to ensure that oil does not get on them. Defective pillows must be replaced.