Thermostat setting diagnostics for internal combustion engine

Apparatus for measuring the operation of the thermostat mounted in an engine cooling system with the engine running, comprising:

• pressure sensor means adapted to be disposed to sense the pressure of the coolant of the cooling system, and providing a pressure signal in response thereto;
• temperature sensor means adapted to be disposed to sense the temperature of the coolant in said cooling system and provide a temperature signal in response thereto;
• speed sensor means, including means adapted to be disposed to sense rotation of the engine, for providing a speed signal indicative of the speed of rotation of the engine;
• signal responsive means for providing in response to signals applied thereto a manifestation of thermostat operation;
• and
• processing apparatus comprising means operative in response to said pressure signal, said temperature signal and to said speed signal with all of said sensor means disposed as described hereinbefore for successively sampling all of said signals in an interspersed fashion, for continuously comparing successively sampled values of said pressure signals and of said temperature signals, respectively, and in response to variation in either of them by an amount sufficient to indicate thermostat operation, providing signals to said signal responsive means to cause it to provide a manifestation of thermostat operation, and for continuously comparing successively sampled values of said speed signal and in response thereto terminating said interspersed sampling in response to said speed signal values indicating an excessive variation in the speed of said engine.

Apparatus for measuring the operation of the thermostat mounted in an engine cooling system having a thermostat bypass with the engine running, comprising:

• sensor means adapted to be disposed for response to parameters of the coolant of the cooling system which are indicative of thermostat operation and indicative of the temperature of coolant circulating in the cooling system through the bypass, and for providing signals indicative thereof;
• signal responsive means for providing in response to signals applied thereto a manifestation of thermostat operation;
• and
• processing apparatus comprising means operative in response to the signals of said sensor means with said sensor means disposed as described hereinbefore for successively sampling signals of said sensor means, for comparing values of said signals indicative of thermostat operation and in response to a significant variation therein providing signals to said signal responsive means to cause it to provide a manifestation of the operation of said thermostat, and for comparing values of said signals indicative of temperature of the coolant circulating in the cooling system through the bypass and terminating said successive samplings in response to indications that the thermostat is stuck in one position.

Apparatus for measuring the operation of the thermostat mounted in an engine cooling system having a thermostat bypass with the engine running, comprising:

• sensor means adapted to be disposed for response to the temperature of coolant circulating in the cooling system through the bypass and providing a temperature signal indicative thereof;
• pressure sensor means adapted to be disposed for response to the pressure of the coolant circulating in the cooling system with the thermostat closed and providing a pressure signal indicative thereof;
• and
• processing apparatus operative in a repetitive process in response to said sensor means with said sensors disposed for response as described hereinbefore, for successively sampling all of said signals, for comparing successively sampled values of said signals, for providing, in response to sensing either a variation in said temperature signal values or a variation in said pressure signal values indicative of thermostat operation, a manifestation of thermostat operation and terminating said process, and for otherwise terminating said process in response to successively samples values of said temperature indicating a failure of said temperature to maintain a given temperature rise per unit of time, said temperature exceeding the rated temperature of the thermostat by on the order of several degrees, or said process having continued over a period of time of on the order of several minutes after said temperature first reaches a given temperature which is a substantial fraction of the rated temperature of the thermostat.

In the method of measuring the operation of the thermostat mounted in the cooling system of an engine, the steps of:

• operating the engine so that the temperature of the coolant in the cooling system will increase from a temperature below the rated thermostat temperature;
• monitoring parameters of the coolant in the cooling system including temperature and pressure;
• and
• providing, in response to a change in one of said parameters sufficient to indicate thermostat operation, an indication of one of said parameters.