Practical Automotive Maintenance: Thermostats
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Thermostats
07.18
| 00:00 | Automotive thermostats serve as the primary regulator of engine temperature. |
| 00:05 | These function as temperature controlled valves positioned between the engine block and the radiator, determining when and how much coolant flows through the cooling system. |
| 00:14 | When starting a cold engine, the thermostat remains closed, blocking coolant flow through the radiator and directing it either partially or entirely through the engine's water jackets. |
| 00:25 | This closed position accelerates the warming process, reducing the time needed for the engine to reach its ideal operating temperature. |
| 00:32 | As engine temperature increases, the thermostat gradually opens, allowing some coolant to flow through the radiator. |
| 00:39 | This regulated circulation creates a balance that prevents both overheating, which can cause catastrophic engine damage, and running too cold, which leads to increased fuel consumption and excessive emissions. |
| 00:51 | Through this continuous modulation of coolant circulation, thermostats ensure that the engines maintain their ideal operating temperature, regardless of the external conditions or engine load. |
| 01:02 | The ideal operating temperature changes for different applications, but is typically between 80 to 95 degrees Celsius. |
| 01:10 | When an engine is cold, fuel doesn't vaporise as effectively, leading to higher emissions and increased fuel consumption. |
| 01:17 | To counter this, OEMs use thermostats to bring the engine up to temperature as quickly as possible by limiting coolant flow to the radiator. |
| 01:25 | And once the engine is up to its ideal temperature, we focus on maintaining these ideal operating conditions, resulting in cleaner emissions output. |
| 01:33 | While this may or may not be relevant to us in the aftermarket or in motorsport applications, emissions output is high on the priority list and is often the primary concern when making design and development decisions. |
| 01:45 | If you'd like to dive deeper into the emissions world, make sure you check out our new emissions course which is linked below this module. |
| 01:52 | Automotive thermostats employ several distinct designs, with what's known as a wax pallet thermostat being the most prevalent. |
| 02:00 | This design uses a brass or copper cylinder filled with a paraffin wax that undergoes a phase change from solid to liquid as the temperature increases. |
| 02:09 | The temperature at which the thermostat starts to open is a case-by-case situation, but it's typical for most thermostats to start opening when the coolant temperature reaches approximately 80 degrees celsius. |
| 02:20 | When this happens, the wax in the thermostat begins melting and expanding. |
| 02:24 | The expanding wax then pushes against the piston or rod connected to the thermostat valve. |
| 02:30 | As the piston extends, it opens the valve allowing the coolant to float through the radiator. |
| 02:35 | When the engine cools, the wax solidifies and contracts and a return spring closes the valve, limiting or stopping flow again. |
| 02:42 | The temperature specified on a thermostat is usually the temperature at which it begins to open at, and it won't be fully open until a higher temperature. |
| 02:51 | For example, an 80 degree rated thermostat will begin opening at the 80 degree mark, but it may not become fully open allowing maximum flow until 95 degrees. |
| 03:01 | Alternative thermostat designs include bimetallic types that use a temperature responsive metal strip, and more advanced electronic thermostats that incorporate heating elements that are pulse width modulated and controlled by the vehicle's engine control unit. |
| 03:16 | These electronically controlled thermostats offer enhanced precision and can adjust opening temperatures based on the driving conditions, rather than responding solely to the coolant temperature, providing additional efficiency benefits in modern vehicles. |
| 03:30 | In motorsport settings, the decision to use a thermostat often depends on the specific racing conditions, engine design and cooling requirements. |
| 03:38 | Many race cars operate without thermostats to remove a potential failure point and maximize coolant flow during high stress competition. |
| 03:46 | This approach allows for an immediate cooling response when engines generate extreme heat under full throttle conditions, and also removes a potential failure point from the engine. |
| 03:57 | Drivers and teams typically develop specific warm-up routines to ensure the engines reach appropriate temperatures before competition, despite the absence of a thermostat, and often modify components of their cooling system to suit, including the addition of different radiator blanking plates to match varying ambient conditions. |
| 04:15 | Removing the thermostat without any other modification could potentially create unexpected challenges, like extended warm-up times or an unrestricted coolant flow that can result in a loss of system pressure and laminar flow, preventing effective heat transfer. |
| 04:31 | Usually, when the thermostat is removed, either a restrictor plate will be used in its place to prevent this, or the stock thermostat will be modified to remove the thermostat component, essentially turning it into a restrictor plate. |
| 04:44 | This explains why some high performance applications retain thermostats, but use lower temperature variants to begin opening sooner than standard units. |
| 04:53 | For example, Nismo has developed thermostats for OEM applications that open 10 degrees colder than the stock Nissan variant. |
| 05:01 | This means our thermostat can open earlier and keep us in a temperature range better suited to motorsport use. |
| 05:07 | For motorsport and racing use, there can be some benefits in running the engine a little cooler than stock as it can make the engine less prone to an abnormal type of combustion called knock or detonation. |
| 05:19 | This can quickly destroy an engine, so anything we can do to reduce the chance of it happening is a benefit. |
| 05:25 | It's worth noting that this is often coupled with an aftermarket radiator that has different flow characteristics and typically a much better heat dissipation capacity. |
| 05:34 | Dealing with motorsport applications requires careful monitoring of the engine temperatures and a full understanding of each component of our cooling system to detect any cooling system irregularities before jumping the gun and simply removing the thermostat as a bandaid. |
| 05:49 | There's no one answer for all situations and applications and some vehicles will benefit while others won't, so it's important to understand the installed components in our cooling system as well as its intended use to make informed decisions. |
| 06:03 | Let's summarise what we've covered in this module. |
| 06:06 | Automotive thermostats are vital to a vehicle's cooling system regulating engine temperature by controlling coolant flow between the engine and radiator. |
| 06:14 | These temperature sensitive valves often hold an intermediate position to fine tune circulation. |
| 06:20 | When the engine is cold, the thermostat stays closed to increase the warm up and then gradually opens as temperatures rise, allowing coolant to flow and preventing overheating or underheating. |
| 06:31 | This also helps reduce emissions by reaching optimal operating temperatures quickly. |
| 06:36 | Most thermostats use a wax pallet design where melted wax expands and pushes a piston to open the valve. |
| 06:42 | Other types include bimetallic and electronically controlled thermostats managed by the ECU. |
| 06:48 | In motorsport, thermostat uses vary by setup. |
| 06:52 | Some race cars omit them for maximum coolant flow, but this can lead to longer warm ups or inefficient heat transfer due to the coolant moving too quickly. |
| 07:01 | High performance builds may use lower temperature thermostats often paired with aftermarket radiators for improved cooling. |
| 07:09 | Proper system understanding and temperature monitoring are key when adjusting thermostat strategies and racing environments. |
