Coolant replacement (every 2 years) (Audi A4 B5)

Drying the cooling system

Warning: Allow the engine to cool before beginning this procedure. Avoid contact with skin or painted surfaces. If contact occurs, rinse immediately with plenty of water. Never leave drained fluid in an open container. Small children and animals may be attracted by the sweet smell of the fluid, and ingestion of the fluid may be fatal.

1. Before draining, unscrew and remove the expansion tank cap. If the engine has not yet completely cooled down, cover the cap with a thick cloth to avoid scalding and slowly unscrew the cap to relieve pressure (usually a whistling sound is heard).

2. If necessary, remove the protective cover of the power unit from under the car. Place a basin under the lower radiator hose. Loosen the clamp of the lower hose, pull it off the radiator nipple and let the liquid drain into the basin. If the hose has not been removed for a long time, shake it with rotational movements on the radiator pipe - do not apply excessive force so as not to damage the radiator. The radiator is equipped with a drain plug, but access to it is possible only after removing the front bumper.

3. If necessary, unscrew the drain plug under the water pump. Remove the old plug seal and replace with a new one.

4. If the coolant is not drained with a chain of its replacement with fresh clean, it can be used again. Manufacturers recommend changing the fluid every two years.



5. Attach the radiator hose to the lower fitting and screw the drain plug back into place (with new seal) under the water pump, tighten it to the specified torque.

Flushing the system

6. If the fluid has not been replaced in a timely manner, or its density has been lost, or it has become cloudy, the efficiency of the cooling system is reduced, since the system channels become clogged with rust and other harmful deposits. The efficiency of the cooling system can be restored by flushing.

7. The radiator is flushed separately from the system so as not to clog its fine channels with dirt washed out of the engine cooling jacket. (The same must be done with the heater radiator).

Radiator flushing

8. To flush the radiator, disconnect its upper and lower hoses - see chapter 3.

9. Insert a garden hose into the upper radiator hose. Direct a stream of clean water into the radiator and flush it until a stream of clean water flows out of the lower hose.

10. If after a reasonable period of time the water does not clear up, you will have to use a cleaning additive, of which there are many in auto shops. Carefully follow the manufacturer's instructions for the additive. If the radiator is quite dirty, remove it and insert a garden hose into the lower branch pipe to flush the radiator in the opposite direction.

Engine flush

11. To flush the engine, first remove the thermostat as described in chapter 3. Temporarily install the thermostat cover.

12. After disconnecting both hoses from the radiator, insert the watering hose into the upper radiator flange and flush the engine with a stream of water until clean water comes out of the lower hose.



13. After flushing is complete, set the thermostat as described in chapter 3 and connect the hoses to the radiator.

Filling the cooling system

14. Before adding fluid to the system, make sure that all hoses and clamps are in good condition and that the clamps are securely tightened. A mixture of antifreeze and water should be used as a coolant all year round to prevent corrosion of engine components (see next paragraph).

15. Loosen the clamp and slide the heater hose onto the engine shield fitting until a bleed hole appears: do not remove the hose completely.

16. Loosen the mounting screws and remove the expansion tank from the engine compartment. Raise the tank approximately 10 cm above the engine and support it with a wooden block or tie it to the hood.

17. Unscrew and remove the expansion tank cap. Slowly fill the system with liquid, without creating bubbles.

18. If the fluid is being replaced, first add a couple of liters of water, then the required amount of antifreeze and add the remaining water.

19. Fill the fluid until it flows out of the bleed hole in the nipple on the engine shield. As soon as the fluid flows out, pull the hose onto the nipple and tighten the clamp.

20. As soon as the level in the expansion tank starts to rise, squeeze the upper and lower radiator hoses several times to help release air locks. Fill the liquid to the MAX mark. Screw the tank cap back on and secure it in place.

21. Start the engine (not exceeding 1500 min⁻¹) and let it warm up for about three minutes. Let the engine idle until the lower radiator hose becomes hot.



22. Check for leaks, especially around the disturbed components. Check the fluid level in the expansion tank and top up if necessary. Note that the engine must be cold when checking the level. If you open the expansion tank cap on a hot engine, cover it with a thick rag and unscrew it slowly to relieve pressure (a whistling sound is usually heard) Wait until the pressure is completely released before unscrewing the plug completely. Never unscrew the plug directly on a hot engine.

Mixing Antifreeze

Warning: models produced before June 1996 were filled with antifreeze catalog number VAG G011A8C (green color). Models produced after July 1996 are filled with antifreeze, VAG catalog number G012A8D (red color). DO NOT MIX these antifreezes in any proportions - you can seriously damage the engine. If there is brown antifreeze in the expansion tank, it means that the system has been filled (refilled) antifreeze of the wrong type. If you are not completely convinced that you know the type of antifreeze that has been filled in, or there is a suspicion that foreign antifreeze has entered the system, the best solution is to drain this compote, rinse the system and fill it with the prescribed type of antifreeze.

23. Antifreeze should always be replaced at the prescribed replacement intervals. This is necessary not only from the point of view of maintaining the antifreeze properties of the liquid, but also because modern anti-corrosion additives lose their properties and a change of liquid is required to prevent engine corrosion.



24. Always use non-ethylene glycol based antifreeze, which is most suitable for systems with mixed metal components. The percentage composition of the antifreeze and water mixture and the freezing point are given in Specifications.

25. Before adding antifreeze, the cooling system must be drained, flushed if possible, and its condition checked all hoses.

26. After filling the coolant, a tag indicating the concentration of antifreeze and the date of filling must be attached to the expansion tank. All subsequent toppings must be performed using antifreeze of the same brand and concentration.

27. Do not use antifreeze in the washer system, as it may damage the paintwork of the body. Other liquids are intended for filling the washer system.