Replacing the cylinder head gasket of the ZMZ-405, -406 GAZ-2705 engine
The cylinder head gasket is replaced if it is damaged
Main signs of head gasket damage:
- - insufficient compression - below 1 MPa (10 kgf/cm 2) in one or more cylinders;
- - breakthrough of gases into the cooling system (seething, foaming of liquid in the radiator, rapid drop in the liquid level in the expansion tank in the absence of external leaks);
- - ingress of coolant into the lubrication system (emulsion on the oil level indicator, separation of oil drained from the crankcase, especially noticeable in a transparent container);
- - oil getting into the cooling system (oil film on the surface of the liquid in the expansion tank).
Removing the cylinder head
The cylinder head can be removed with the receiver and exhaust manifold.
If the cylinder head is removed from an engine installed on a car, you must first perform the following operations:
Disconnect the fuel supply and drain lines.
Remove the battery.
Remove the hood.
Unscrew the six bolts 1 and remove the front engine mudguard 2.
Drain the engine cooling system.
Remove the ignition coils.
Disconnect the phase sensor connector from the wiring harness.
Unscrew the screws and disconnect the wires from the oil pressure indicator 1 and emergency oil pressure 2 sensors.
Disconnect the connectors from the engine temperature sensors 5, coolant temperature indicator 4, coolant overheat indicator 3.
Loosen the clamp and remove the hose to the expansion tank from fitting 6 of the thermostat.
Loosen the tightening of clamp 1 and remove hose 2 from the fitting to the check valve of the vacuum brake booster.
Disconnect connector 3 from the throttle position sensor.
Unscrew nut 1 and remove the blue ground wire from the stud at the front end of the receiver.
Unscrew nut 4 and pull out accelerator cable 3 from the air throttle valve drive sector.
Disconnect plug 2 from the wiring harness, located between the engine intake pipes, the speed sensor and the crankshaft synchronization sensor installed near the ring gear of the crankshaft pulley.
Move the cable gland 3 from the threaded end 2 of the cable shell, unscrew the nut 1 securing the cable end and pull out the end 2 from the bracket fixed to the engine intake pipe, sliding it back.
Then remove the accelerator cable from the bracket upwards.
Bend the accelerator cable holder and remove the cable from it. Move the accelerator cable away from the engine.
Disconnect the wires from the generator.
Disconnect connector 1 from the idle speed control.
Unscrew nut 2 and remove the ground wires from the stud at the rear end receiver.
Disconnect connector 1 from the air temperature sensor.
Loosen clamp 2 and remove the coolant supply hose from the heater tap fitting
Disconnect connectors 1 from the injectors. Unbend the holders of 2 wire harnesses and remove the harness from the holders.
Place the wiring harness away from the engine.
Then disconnect the muffler intake pipe from the exhaust manifold, disconnect the hose from the throttle body, remove the radiator supply pipe, remove the generator.
Then the procedure for removing the cylinder head from an engine removed from a car and from one installed on a car is the same.
Remove the camshafts.
Loosen the tightening of clamps 1 and remove hoses 2 and 3 from the throttle body fittings.
Remove the thermostat with the housing.
Remove the spark plugs.
Unscrew bolts 1 securing the cylinder head. Remove bolts 1 and washers.
Remove the cylinder head and head gasket.
Do not drive screwdrivers or any other tool between the cylinder head and the cylinder block, as this may damage the surface of the cylinder head adjacent to the cylinder block.
Installation
Install the block head in the reverse order of removal.
The procedure for tightening the cylinder head bolts is shown in the figure.
Tighten the cylinder head mounting bolts in two stages:
- - 1st stage - 40–60 N m (4.0-6.0 kgf m);
- - 2nd stage - 130-145 N m (13.0-14.5 kgf m).
