Check the fluid level and, if necessary, add fluid after the thermostat opens.
For models «525», «528», whose cooling system includes an expansion tank, the system is filled through the radiator filler neck.
Open the heater tap and start the engine. After the engine has warmed up, bleed the air from the system by loosening the bleed screw. Add fluid to the expansion tank until it flows out without bubbles, then tighten the bleed screw.
Stop the engine, relieve pressure in the cooling system by unscrewing the radiator cap to the first detent position, and add fluid to the normal level.
Checking the tightness of the cooling system
Remove the radiator cap and replace it with a hand pump with a pressure gauge. Create a pressure of up to 1 kg / cm2 with a pump, which should not decrease within 1-2 minutes.
A safety valve is built into the radiator cap, which must open when the pressure indicated on the cap is reached.
Thermostat
Check the opening temperature of the main thermostat valve, which should be 80±1.5°C for models «518», «520» or 84°C for models «525», «528».