Thermostat
Fits AUDI A4 B9 (8W2, 8WC) 40 TDI
(2015)

What is a engine thermostat?

An engine thermostat is a valve like device responsible for the control of the water / coolant when the engine reaches a specific temperature. A correctly functioning thermostat is important for the engine to reach its optimum operating temperature which improves efficiency and reduces engine wear.

There are different types of engine thermostat. These are:

• Conventional thermostat

• Electrically heated thermostats

• Electrically actuated thermostats

What comes with a thermostat?

Engine thermostats are available with a number of different additional parts included however these vary depending on the aftermarket maker and the requirements of the vehicle.

The parts that come with a thermostat are normally shown in the stock image or are listed in the parts notes. Items that can be included are:

• Gasket or seal

• Housing or flange

• Sensor or switch

How do I choose the correct thermostat?

There are different temperature ratings for engine thermostats. These rating show the temperature that the thermostat operates. Often the temperature ratings are different depending on the climate of the country the car is destined for. The temperature rating is often noted on the thermostat itself which can be useful when selecting a replacement. There can be different thermostats listed as compatible and unless you compare the original part number it can be unclear which is the correct one.

Here are some factors to consider:

• Manual or automatic transmission

• Temperature rating (°C)

• Vehicle manufacture date (this is not the date the vehicle was registered but the date it was made

• Engine number sequence (up to or after as specific number/letter

• VIN (chassis number) sequence (up to or after as specific number/letter

What brand of thermostat should I choose?

There are many aftermarket makers of thermostats so there are plenty of options. Makers such as Valeo, Sachs and Bosch make parts for the original vehicle manufacturers so these would be classed as premium. Aftermarket brands such as Gates, Febi, Blue Print and Quinton Hazell offer long warranties which is a great indicator of quality. The choice is largely down to your budget and the brand you are comfortable with.

How can I tell my thermostat needs replacing?

A faulty engine thermostat will cause problems with how your engine heats up. If you are not sure if you have a faulty thermostat we’d advise that you speak to a qualified mechanics however here are some symptoms of a faulty or failing thermostat:

• Engine overheating

• Engine takes a long time to warm up

• Heater takes a long time to produce heat

• Erratic engine temperatures

• Coolant leaking