A thermostat includes: a thermostat housing having an inlet and an outlet; an internal housing having a main valve hole and a fail-safe hole, wherein the internal housing is disposed within the thermostat housing and internal housing and has a main chamber communicating with the inlet of the thermostat housing; a wax housing disposed within the internal housing and having a first wax and a second wax; a first valve selectively opening or closing the main valve hole according to expansion or shrink of the first wax; and a second valve selectively opening or closing the fail-safe hole according to expansion or shrink of the second wax.

Fluid temperature regulator includes a unitarily-formed housing having an inlet, outlet, bypass outlet, and plurality of valve chamber openings, in line with respective valve chambers. Valve holders are removably disposed within valve chamber openings to position thermostatic valves within the valve chambers. Each valve holder includes at least one wall having at least one holder outlet opening and holder bypass outlet opening. First and second regulator flowpaths through the regulator are defined through the regulator inlet to either the regulator bypass outlet or regulator outlet depending upon whether the thermostatic valves is disposed in a first or second configuration, respectively.

A valve device with fail-safe mechanism capable of improved production efficiency includes a valve element, a valve element housing, a third communication port provided in the valve element housing, and a fail-safe mechanism. The fail-safe mechanism includes a thermo-element and an element housing that houses the thermo-element. The element housing has a large-diameter housing, a small-diameter housing portion that accommodates the thermo-element, and a step. A valve element communicating portion communicating with the valve element housing is provided to the small-diameter housing portion. The fail-safe mechanism includes a valve plate member for closing the step and a coil spring that biases the valve plate member. A third adapter provided to the third communication port is provided with a through-hole that enables the large-diameter housing portion and the third communication port to communicate with each other.

A failure diagnosis method of a coolant temperature sensor for a vehicle, may include determining, by a controller, whether or not it is in a flow stop state that stagnates the flow of coolant by a flow control valve; obtaining, by the controller, an engine outlet coolant model temperature when it is in the flow stop state; and diagnosing, by the controller, as a failure of an engine outlet-side outlet water temperature sensor when the coolant model temperature is equal to or greater than a reference temperature and the flow stop state is maintained by the flow control valve.

Methods and systems are provided for a cooling system valve comprising a fusible insert and a heating element coupled to the insert. In one example, in response to an increase in coolant temperature to above a first threshold temperature, a movable element of the cooling system valve may be actuated to a fully open position and in response to an increase in coolant temperature to above a second threshold temperature with the movable element in a fully open position, electric current may be routed through the heating element to heat and melt the fusible insert. By melting the fusible portion, coolant may flow through an opening created in the movable element.

A cooling control device for an internal combustion engine has an internal coolant passage formed in the internal combustion engine, external coolant passages formed outside the internal combustion engine and connected to the internal coolant passage, the cooling control device performing coolant passage switching in which the internal coolant passage and a certain one of the external coolant passages are connected to or disconnected from each other by a circuit switching mechanism, a branching passage that sends coolant in the internal coolant passage to one of the external coolant passages which passes through a radiator, when the circuit switching mechanism has a failure and fails in circuit switching of connecting the internal coolant passage and the external coolant passage passing through the radiator to each other, and a wax-type thermostat provided in the branching passage that opens the branching passage when the internal combustion engine is excessively heated.

Systems and methods are disclosed for determining a temperature of a coolant in a cooling system for an engine and diagnosing a thermostat in the engine responsive to the determined temperature. A system includes a liquid cooling system including a thermostat, the liquid cooling system structured to circulate a coolant, and a controller coupled to the liquid cooling system and the EGR system. The controller is structured to: receive engine heat data indicative of a first amount of heat introduced into an engine; receive heat loss data indicative of an amount of heat loss experienced by the coolant; determine a temperature of the coolant based on the first amount of heat and the amount of heat loss; compare the determined temperature of the coolant to a sensed temperature of the coolant; and determine a status of the thermostat responsive to the comparison.

Systems and methods are disclosed for determining a temperature of a coolant in a cooling system for an engine and diagnosing a thermostat in the engine responsive to the determined temperature. The system and method includes interpreting engine heat data indicative of a first amount of heat introduced into the internal combustion engine; interpreting exhaust gas recirculation (EGR) heat data indicative of a second amount of heat introduced into the internal combustion engine via the amount of exhaust gas provided to the intake manifold; interpreting heat loss data indicative of an amount of heat loss experienced by the coolant; determining a temperature of the coolant based on the first amount of heat, the second amount of heat, and the amount of heat loss; comparing the determined temperature of the coolant to a sensed temperature of the coolant; and determining a status of the thermostat responsive to the comparison.

Provided is a thermostat monitor (36) comprising a thermostat open failure detecting part (38) for detecting an open failure of a thermostat when a condition is such that a radiator heat radiation amount (14) radiated from a radiator on a radiator-side cooling water channel is larger than a heater core heat radiation amount (12) radiated from a heater core on a heater core-side cooling water channel, and that a difference between the radiator heat radiation amount and the heater core heat radiation amount is equal to or more than a predetermined value A. Based on a temperature of engine cooling water detected by a temperature sensor positioned in the vicinity of an outlet of an in-engine cooling water channel, it is possible to detect the open failure of the thermostat relatively easily with certainty.

A control method of a coolant control valve unit that rotates a cam using torque of a motor and allowing a profile formed on the cam to push a rod to allow the valve formed on the rod to open/close a coolant passage, including steps of: rotating the cam by operating the motor; detecting a rotation position of the cam; determining a stuck state in which the cam or the motor is not rotated while the motor is operated; and performing an escape mode in which if it is determined that the cam or the motor is in the stuck state, the motor outputs a predetermined torque to the cam side in a predetermined rotation direction to escape the cam from the stuck state.