Audi A3 - Heat output too low | HELLA



Model years 1997 to 2003

All engines with cast-iron cylinder block

Heat output too low

If a customer complains about the above error, this could be caused by contaminated engine coolant.

Such contamination (rust, metal particles from the cast-iron block) blocks the small openings in the heat exchanger preventing flow.

In this case, proceed as follows:

- Drain the coolant from the engine.

- Remove the thermostat housing, remove the thermostat and refit the housing.

- Fill the cooling system with fresh water and HELLA cleaning agent for cooling systems 8PE 351 225-841.

- Vent the cooling system.

- Warm up the engine. Set the heating to maximum and then let the engine idle for 10 minutes.

- Turn off the engine and leave it to cool.

- Drain the fluid from the system.

- Refill the system with clear water and vent the system.

- Warm up the engine.

Check heat output. If output has not improved, the heat exchanger must be replaced.

- Drain off the fluid again.

- Refit the thermostat. In such cases, it is recommended that the thermostat is also replaced.

- Fill the cooling system as per manufacturer’s instructions (correct coolant and correct mixing ratio).


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The following technical information and tips for practical use have been set up by HELLA in order to offer professional support to automotive workshops in their daily work. The information available here on this website is only to be used by appropriately trained specialist staff.

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