Replacing the cylinder head gasket for the ZMZ-405, 406 GAZ-2705 engine
The cylinder head gasket is replaced if it is damaged
The main signs of damage to the head gasket:
—insufficient compression — below 1 MPa (10 kgf/cm2) 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, stratification of oil drained from the crankcase, especially noticeable in a transparent container);
- oil ingress into the cooling system (oil film on the surface of the liquid in the expansion tank).
Removing the cylinder head
The head of the block can be removed with the receiver and exhaust manifold.
If the head of the block is removed from the engine installed on the car, you must first perform the following operations:
Disconnect the fuel supply and return lines.
Remove the battery.
Remove the hood.
Remove the six bolts 1 and remove the front mudguard 2 of the engine.
Drain the engine cooling system.
Remove the ignition coils.
Disconnect the phase sensor plug from the wiring harness.
Remove the screws and disconnect the wires from the sensors for oil pressure indicator 1 and emergency oil pressure 2.
Disconnect plug connectors from engine temperature sensors 5, coolant temperature gauge 4, coolant overheat indicator 3.
Loosen the clamp and remove the hose to the expansion tank from fitting 6 of the thermostat.
Loosen clamp 1 and remove hose 2 from the fitting to the non-return valve of the brake booster.
Disconnect connector 3 from 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 accelerator cable 3 out of the air throttle actuator sector.
Disconnect from the wiring harness plug 2, located between the engine intake pipes, the speed sensor and the crankshaft synchronization, installed near the crankshaft pulley ring gear.
Slide the cable gland 3 from the threaded lug 2 of the cable sheath, unscrew the nut 1 securing the cable lug and pull the lug 2 out of the bracket fixed to the engine intake pipe by sliding it back.
Then pull the accelerator cable upwards out of the bracket.
Pull back 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 controller.
Unscrew nut 2 and remove the ground wires from the stud at the rear end of the receiver.
Disconnect plug 1 from air temperature sensor.
Loosen clamp 2 and remove the coolant supply hose from the heater tap fitting
Disconnect connectors 1 from the injectors. Unbend holders 2 of the wiring harness and remove the harness from the holders.
Move the wiring harness away from the engine.
Then, disconnect the exhaust pipe from the exhaust manifold, disconnect the hose from the throttle body, remove the radiator supply pipe, remove the generator.
Further, the procedure for removing the head of the block from the engine removed from the car and from the one installed on the car is the same.
Remove the camshafts.
Loosen clamps 1 and remove hoses 2 and 3 from throttle body fittings.
Remove thermostat with housing.
Remove the spark plugs.
Remove the bolts 1 securing the block head. Remove screws 1 and washers.
Remove the cylinder head and head gasket.
Do not drive a screwdriver 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.
Install the block head in the reverse order of removal.
The order of tightening the block head bolts is shown in the figure.
Tighten the block head bolts in two steps:
- - 1st stage - 40–60 N m (4.0–6.0 kgf m);
- - 2nd stage - 130–145 N m (13.0–14.5 kgf m).