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Volvo Diesel Engine Cooling Tests

Jun. 26, 2018

Cooling Tests, General



A number of terms are used to define cooling system capacity. Maximum ambient temperature. The maximum ambient temperature the machine may be used in without exceeding the permissible water temperature.

Volvo Diesel Engine Cooling Tests.jpg

Δt water (delta t) - the temperature differential between radiator inlet and outlet


Δt air - the temperature differential between radiator inlet and outlet air.

Cooling capacity

A cooling system installation's cooling capacity is often measured using a reference temperature for coolant boiling point called ATB (Air To Boil). The ATB temperature is defined as the ambient temperature at which the coolant attains its maximum permissible coolant temperature. AOT (Air On Temperature) refers to the maximum permissible coolant temperature after the Volvo engine. It is defined as the temperature of the cooling air entering the charge air cooler. The difference between AOT and ATB temperatures is that the input cooling air temperature is used instead of the ambient temperature.

The maximum permissible temperatures for each engine type are given in Technical data, in Sales Support Tool, Partner Network This concerns unpressurized cooling systems. If the system is fitted with a pressure cap or pressure valve the boiling point will rise according to the pressure setting value.



Cooling Test Preparation

Before the application is prepared for a cooling test it is extremely important to ensure that the installation in general is satisfactory. If any adjustments are necessary as a consequence of the tests, and which may affect cooling in particular, such changes must be made at this stage. It is also extremely important to have accurate and reliable instruments available, as well as other equipment and aids recommended for performing the cooling tests. Sometimes all the recommended equipment may not be available, but remember that the main objective is to ensure that the application is tested under a load cycle that corresponds to the most difficult conditions the application can be exposed to during use.


If there is any uncertainty about how difficult the conditions the application will be exposed to will be, we recommend always to attempt maximum output at rated rpm. Measuring instruments must be installed at the recommended locations. All tests must be performed with a fixed open thermostat. A short test run must be made to check that all parts with temperature probes attached are functioning correctly. The test must be carried out in dry conditions with a wind speed that does not exceed 7 m/s (23 ft./s) and preferably with an ambient temperature above +5 °C (+41 °F). Before the cooling test is carried out, exhaust back pressure must be determined at rated rpm under full load.


Air filter resistance must be determined with the engine at maximum rated rpm and load. Regardless of the type of application being tested, the maximum load condition expected during application use must be determined. One practical method of determining maximum load conditions is to check exhaust gas temperature. When the maximum load condition has been determined, the application must be run continually at this load until temperatures have stabilized. This usually takes 50 to 60 minutes. The installation checks must be concluded with a technical report that includes all test results, a detailed description of the installation and a conclusion.



For More Volvo Engine workshop information, please visit:

Volvo Engine Compressed Air Filter

Volvo Engine Appraisal and Testing





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