Contents: Replacing the thermostat - 1.1/1.3 l…↓ Replacement - 1.5/1.6/1.8 l engines ↓ Checking the Thermostat ↓
If a faulty thermostat gets stuck in the closed position, it will cause the engine to overheat; if the thermostat is constantly open, the engine will take too long to warm up. The thermostat cannot be repaired; if it is defective, it should be replaced. Make sure that the new thermostat has the correct markings, which are usually located on its base.
Please note that since August 1978, thermostats with a higher opening temperature have been installed than on previous engines.
Replacing the thermostat - 1.1/1.3 l engines
The thermostat is located in the water outlet pipe at the rear end of the cylinder head.
Disconnect the lower radiator hose and drain the cooling system until the level is below the thermostat.
Disconnect the upper hose from the cylinder head. Unscrew the thermostat pipe mounting bolts and remove the thermostat (figure E:5).
Clean the thermostat housing seat and install a new thermostat. It is important to install the thermostat in the correct position - if the thermostat is installed incorrectly, the engine will overheat. Install the thermostat hose with a new sealing ring.
Secure the hoses and add coolant to the system.
Start the engine, warm it up to operating temperature and check the thermostat operation. Check the system for leaks. Check the coolant level again on a cold engine.
Replacement - 1.5/1.6/1.8 l engines
Replace the thermostat as described above. The thermostat is located under the lower hose of the cooling pump (Fig. E:4).
When replacing the thermostat, install a new O-ring on the hose. Make sure the thermostat is positioned correctly when installing.
Checking the Thermostat
If you have any doubts about the thermostat's functionality, remove it from the engine. The thermostat's functionality can be checked (for the thermostat opening temperature, see the section "Technical data").
(The original text is available on the portal: VWMANUAL)
If the thermostat, removed from a cold engine, is open at room temperature, it is faulty - replace it.
1. If the thermostat is closed, hang it in a glass filled with water so that it does not touch the walls or bottom (figure E:6).
2. Heat the water gradually, checking its temperature with an accurate thermometer.
3. If the thermostat does not open when the required temperature is reached, does not open completely, or does not open at all, replace it.
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