Coolant​ ​thermostat:​ ​common​ ​defects​ ​and​ ​their​ ​signs

1. Jamming.
   • Engine temperature increases.
   • Fuel consumption increases.
   • Unstable engine thermal condition during driving.
2. Soiling, corrosion.
   • The engine cannot warm up to working temperature.
   • The heating system functions inefficiently.
   • Constant engine overheating.

How to replace coolant thermostat?

Generally, it is recommended to replace the coolant thermostat every 2 years or every 80,000–100,000 operational kilometres. A broken thermostat cannot be repaired and requires replacement.

When choosing a new component take into account vehicle technical documentation. The thermostat should have matching response temperature and fit the engine type.

You can replace component on your own since the procedure is rather simple. The order differs a little for cars of different models; generally to replace the component you need to do the following:

1. Drain cooling liquid into the prepared tank.
2. Unscrew nuts on the thermostat housing cover.
3. Remove the housing cover. Remove the thermostat and then its sealing ring.
4. Install a new thermostat with a new sealing ring.
5. Mount the housing cover, treat it with sealing compound, screw connections and pour cooling liquid inside.
6. Start the engine and make sure there’s no antifreeze leakage.

Thermostat replacement is performed only after cooling down of a car engine.

It is important to follow safety regulations during unsupervised replacement of the cooling system thermostat.
Before starting thermostat diagnostics or replacement, you should wait until full cooldown of cooling liquid.
When installing a new thermostat, replacing its gasket is a must. If operational lifetime of cooling liquid is ending (its lifetime limit is 4 years) then it is to be replaced as well.
Average operational lifetime: 4 years or 100 000 km.

Types:

1. By presence of a housing:
   • with a housing;
   • uncased.
2. By presence of a heating resistor.
   • with a heating resistor;
   • without a heating resistor.