GB2530736A

GB2530736A - Engine Cooling System

Info

Publication number: GB2530736A
Application number: GB1417210.0A
Authority: GB
Inventors: Andrew Pugh
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2014-09-30
Filing date: 2014-09-30
Publication date: 2016-04-06
Anticipated expiration: 2034-09-30
Also published as: RU2015139502A3; GB2530736B; DE102015116407A1; RU2701037C2; MX2015011551A; GB201417210D0; RU2015139502A

Abstract

The system comprises an engine 6 having an inlet to receive coolant into the engine and a return circuit that returns coolant to the inlet. The return circuit includes a radiator branch 8, a bypass branch 9 and a degas branch 11 connected to a degas tank 12. A flow controller is operable to open/close the degas branch to allow/prevent flow of coolant to the degas tank. Preferably the inlet comprises a pump 5, and a thermostat 7 distributes coolant from the engine to the radiator branch or bypass branch depending upon the temperature of the coolant. A heater branch leading to a heater module 10 for a passenger cabin may also be included. The flow controller may comprise a valve 20 or a degas branch line (23, figure 5) and may be opened/closed based upon a computer generated model of the current or anticipated gas volume within the coolant so that the system is de-aerated only when needed. A cooling system including a flow controller that operates independently of engine temperature is also claimed.

Description

ENGINE COOLING SYSTEM

The present invention relates to an engine cooling system and to a method of cooling an engine. More specifically, the present invention relates to an engine cooling system having a degas tank for eliminating gases from the coolant and to associated methods.

Background

It is usual for combustion engines to incorporate a cooling system for removing waste heat to thereby prevent overheating of engine pads. A typical cooling system utilises a fluid coolant which is circulated through the engine by means of e.g. a pump. The fluid may be water or a mixture of mixture of water and other chemicals. Alternatively, a cooling system may utilise a gaseous fluid.

Engine cooling systems typically include a radiator (heat exchanger) and a thermostat.

The thermostat is operable to sense engine temperature and to open or "switch" one or more branches of a return circuit in order to allow heated coolant to exit the engine and flow back to the pump. Specifically, the thermostat is operable to open a radiator branch of the cooling system in order to allow circulation of the heated coolant from the engine to the radiator when the engine reaches a minimum threshold temperature.

When the engine is cold, or is operating below a given threshold temperature, the thermostat is operable to close (or maintain closed) the radiator branch and to open (or maintain open) a bypass branch such that coolant does not circulate through the radiator and is instead circulated back to the coolant pump via the bypass branch. It is also common for a third branch to be provided for taking heated coolant from the engine via a heater module for supplying heat to the passenger compartment via a heater unit.

A combustion engine cooling system requires a means for eliminating gases from the coolant, The source of coolant gases, which increase coolant volume and decrease coolant effectiveness, is predominantly leakage of combustion gases past the cylinder head into the water jacket. This is usually achieved by the provision of a vent line from the engine which leads to a so-called degas tank to which heated coolant can flow and which allows the separation of gases from the heated coolant.

According to previously considered cooling system arrangements, the degas line is provided as part of an engine output circuit such that heated coolant flows to the degas tank and is then returned to an engine input circuit of the cooling system for reci rcu lation, However, according to the previously proposed combustion engine cooling systems, the vent line to the degas tank tends to be permanently open to the engine such that coolant will flow to the degas tank whenever the engine cooling system is in operation.

Thus, flow to the degas tank occurs even when the gas volume suspended in the coolant is low, and degas of the coolant is not required.

It will be appreciated that heated coolant which exits the engine will be replaced by cold coolant from elsewhere in the system. Thus, a problem with previously proposed combustion engine cooling systems is that the engine takes longer to warm up as a result of, potentially unnecessary, coolant flow to the degas tank. Furthermore, coolant flow to the degas tank can also be detrimental to heater performance. This is particularly a problem in cold climates.

It is therefore desirable to provide a cooling system for a combustion engine which seeks to alleviate the problems associated with the previously considered cooling system arrangements.

Statements of invention

According to a first aspect of the present invention there is provided a cooling system for an internal combustion engine comprising an input for receiving coolant into the engine and a return circuit for returning coolant from the engine to the input, wherein the return circuit comprises a radiator branch and a bypass branch and wherein the return circuit further comprises: i) a degas branch connected to a degas tank; and U) flow control means operable to separately open/close the degas branch to respectively allow/prevent the flow of coolant to the degas tank.

Thus, the cooling system comprises an output circuit for circulating heated coolant from the engine, typically via a thermostat, and returning it to the input. The output circuit comprises a number of branches including a radiator branch to allow heated coolant to flow from the engine to a radiator, or heat exchanger, of the system, and a bypass branch to allow heated coolant to flow back to the input.

The flow control means is arranged to switch the flow (i.e. turn on or off) in only the degas branch.

The ability to separately, or independently, open/close the degas branch of the return circuit allows coolant flow to the degas tank to be turned on/off without changing the state of flow-i.e. on/off state -in the other branches.

The ability to switch (on/off) the flow of coolant in the degas branch without changing the state of flow in the radiator or bypass branch, advantageously means that the degas branch can be opened/closed, as required, based on certain conditions being met and/or based on a determination as to whether or not degas is required or beneficial, and regardless of the state of flow in the other branches.

Thus, flow to the degas tank can be allowed, based on a determination that degas is required, or is desirable, and/or when certain conditions are met, without changing the state of flow in the other branches. For example, at operating temperatures above a certain temperature, or based on a determination result that degas is required, or is desirable (for example based on a determination of the current or expected gas volume suspended in the coolant), the degas branch line can be opened through operation of the flow control means without changing the on/off state of coolant flow in the other branches.

On the other hand, through operation of the flow control means, the degas branch can be closed, thereby preventing coolant flow to the degas tank, based on a determination that degas is not required, or is not desirable and/or when certain conditions are met.

For example, at operating temperatures below a given threshold, or based on a determination that the current or expected gas volume suspended in the coolant is sufficiently low so that degas is not required, it may be desirable to prevent coolant flow to the degas tank in order to allow for faster engine warm-up and/or to prioritise flow to the heater unit. Thus, at least within certain engine operating temperatures, the degas branch line can be advantageously closed as/when required through operation of the flow control means without changing the on/off state of coolant flow in the other branches.

Preferably, the return circuit comprises a heater unit which is arranged to receive heated coolant from the engine via a heater branch of the return circuit. The heater branch may be provided as a designated branch of the return circuit or may be provided as a part of the bypass branch. Thus, according to an embodiment of the first aspect, which facilitates separate control of the open/closed state of the degas branch, the flow of coolant to the degas tank can be prevented when demand on the heater unit is high and/or the heater branch is open. Thus, an advantage of this arrangement is that is possible for the engine cooling system to be operated such that flow of heated coolant to the heater unit is prioritised above coolant flow to the degas tank. This leads to an improvement in heater performance which is particularly desirable in cold climates.

Preferably, the return circuit comprises a thermostat operable to switch the flow of coolant between the radiator branch and the bypass branch.

The flow control means may be implemented in a number of alternative ways. For example, flow control means may optionally be implemented by means of a designated valve provided on the degas branch of the return circuit. Such a valve is operable to selectively block the flow of coolant through the degas branch. This arrangement is particularly suited to engine cooling systems which utilise a conventional thermostat operable to switch coolant flow between the bypass branch and the radiator branch.

Alternatively, a flow control means comprising a valve provided on the degas branch may be implemented in connection with an engine cooling system employing an electronically controlled thermostat, with the degas vent line being provided between the thermostat and the degas tank, or between the engine and the degas tank. An advantage of this arrangement is that flow to the degas tank can be controlled by the valve independently from the operation of the thermostat. This enables the flow of heated coolant to the degas tank to be controlled independently of temperature and the switching of the bypass/radiator branches for example, to allow degas to be actively controlled on the basis of conditions other than temperature, such as a determination of the current/expected gas production and/or a determination of the current/expected gas volume in the engine or suspended in the coolant.

Alternatively, the flow control means may be implemented by means of a thermostat and by providing a dedicated degas branch on the thermostat which facilitates an operating arrangement whereby flow through the degas branch can be switched on/off through operation of the thermostat. An advantage of this arrangement is that the active degas control can be implemented without the inclusion of any additional components, such as a valve, which would add cost to the system.

This arrangement is particularly suited to engine cooling systems which employ an electronically controlled (e.g. digital electronic) thermostat.

The electronically controlled thermostat may be operable to be activated sequentially -i.e. a sequenced" thermostat -or may be operable such that the various branches can be activated out of sequence. In the case of a sequenced thermostat, wherein the different branches of the return circuit exiting the thermostat are opened/closed in sequence at different temperatures as the measured temperature rises/falls, the position of the degas branch can be selected according to the priority given to the flow of heated coolant in the branches of the return circuit. Preferably, the degas branch is provided below the radiator branch. Thus, the degas branch can optionally be provided between the heater branch and the bypass branch. Alternatively, the degas branch can optionally be provided between the bypass branch and the radiator branch.

Optionally, according to embodiments of the present invention which utilise an electronically controlled thermostat in conjunction with a switched degas branch on the thermostat, it will be appreciated that the flow control means is operable to separately open/close the degas branch when the engine is operating within a certain temperature range, as defined by the activation temperatures assigned to the switching of the adjacent branches of the thermostat. In these circumstances, the flow control means is optionally operable, within that temperature range, to selectively control switching on/off of the degas branch line independently of temperature -e.g. based on a determination of current or expected coolant gas volume or engine needs. Thus, an electronically controlled thermostat can advantageously be operable to balance the requirements of both temperature control and gas removal with the degas branch being operably connected to the thermostat and being switched in dependence on a determination result rather than in dependence on temperature. The cooling system should preferably be designed so that the need for degas does not conflict with the need for cooling, as it is very likely that both functions will be needed at the same time.

There is, however, no penalty for having un-necessary degas when cooling is called for.

Thus, with the degas branch preferably positioned below the radiator branch, the engine will need to below the threshold temperature for turning on the radiator branch in order for degas line control to be available. However, as preferred embodiments seek to enhance engine warm-up through the provision of degas line control, this is not a problem.

It is envisaged that an engine control module will be operable to actively control the flow control means in order to control the degas process by selectively opening or closing the degas circuit.

Optionally, the flow control means may be operated based on a determination result which takes into account one or more factors including a determination of the current/expected gas volume suspended in the coolant, a determination of the gas production rate of the engine, a determination of the gas volume in the system, temperature or other engine requirements.

Optionally, the flow control means may be operable to open the degas circuit intermittently, for example at particular time intervals e.g. the cooling system may incorporate a timer such that the flow control means can be operable such that the degas circuit is open intermittently for a given time period. The determination of the frequency and duration of the time periods during which the degas circuit is open can be based on a determination of coolant gas volume e.g. a worst case gas volume.

The determination of coolant gas volume can be obtained in a number of ways. For example, it may be obtained by theoretical calculations which provide a worst or best-case gas production rate of the engine. A more preferred solution involves monitoring one or more live parameters e.g. engine speed, load and temperature, which may be utilised e.g. by entering into a computer program, -in order to generate a model of coolant gas volume, whereby the rate of combustion gas production is a function of cylinder pressure and engine speed. Optionally, the model will increment the modelled gas volume when the degas line is closed and decrement the modelled gas volume when the degas line is open for any reason (active degas or for when as a result of other engine requirements). Alternatively, a physical sensor operable to measure coolant gas content may be provided within the cooling system.

Thus, the switching of the degas branch may optionally be based on a computer generated model of the current or expected gas volume -i.e the volume of gas suspended in the coolant. For example, based on the model of gas volume in the system, the degas branch may be operated to open at certain time intervals, for a certain duration. Alternatively, based on the model of gas volume in the system, the degas branch may be opened as and when it is determined to be required, according to the model. By modelling the gas volume in the system/coolant, it is possible to allow/prevent the flow of coolant to the degas tank based on a more accurate assessment of whether or not degas is required so that detrimental heat loss arising as a result of coolant flow to the degas tank can be alleviated.

According to a preferred embodiment, an engine control module is operable to control the switching of the degas branch line of the thermostat based on a determination of the coolant gas volume.

According to a second aspect of the present invention there is provided a method of cooling a combustion engine comprising an input for receiving coolant into the engine and a return circuit for returning coolant from the engine to the input, wherein the return circuit comprises a radiator branch and a bypass branch, the method comprising operating flow control means in order to independently open/close a degas branch of the return circuit in order to allow/prevent the flow of coolant to a degas tank.

Optionally, the method of cooling a combustion engine involves operating the flow control means comprises obtaining a determination result based on consideration of one or more of: coolant gas volume, temperature and engine requirement& According to a third aspect of the present invention there is provided a cooling system for a combustion engine having electronic flow control means for separately/independently controlling the flow of coolant to a degas tank of the cooling system.

Optionally, the flow control means according to any of the above aspects, is operable to open/close the degas branch independently of engine temperature. Optionally, the flow control means is operable to open/close the degas branch based on a determination of the current or expected gas volume suspended in the coolant.

Brief Description of the Drawings

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: Figures 1A and lB schematically show a previously considered engine cooling system; Figures 2A, 23 and 2C schematically show another previously considered engine cooling system; Figure 3 schematically shows a combustion engine cooling system according to a first

preferred example;

Figure 4 shows a combustion engine cooling system according to a second preferred

example;

Figure 5 shows a combustion engine cooling system according to a third preferred

example; and

Figure 6 shows a combustion engine cooling system according to a fourth preferred

example.

Detailed Description

Throughout the Figures the same reference numerals will be used to denote same or similar parts.

Figures 1A and 13 schematically show an example of a previously considered engine cooling system. The system comprises a pump 5 operable to cause coolant to circulate through the engine 6. The engine is connected to a thermostat 7 which is operable to selectively control the flow of coolant either through a radiator branch 8 of the system or, alternatively, through a bypass branch 9. The radiator branch and the bypass branch form part of a return circuit of the cooling system. The system also comprises a heater module 10 connected to the engine output circuit such that heated coolant can be supplied to the heater module and harnessed for providing heat to the passenger compartment of a vehicle before being recirculated back to the pump 5 via the bypass branch 9. A vent line 11, which in this arrangement is connected directly to the thermostat and is in permanent fluid communication with the engine, allows the flow of heated coolant to the degas tank 12 where gases are able to separate from the heated coolant. The degas tank generally comprises a reservoir with a free air surface and a means of venting excess pressure.

Figure 1A shows the circulation of coolant through the system when the engine is cold, or is operating below a threshold temperature. In this state, the thermostat position prevents the flow of coolant through the radiator branch 8 and coolant instead flows directly back to the pump 5 via the bypass line 9 and, if required, via the heater module 10.

Figure 16 shows the circulation of coolant through the system when the engine is hot, or is operating above a threshold temperature. In this state, the thermostat position prevents the flow of coolant through the bypass branch 9 and heated coolant instead flows through the radiator branch 8 through a radiator 13 which serves to remove heat from the coolant before it is returned to the pump 5.

In both states, the vent line is open and heated coolant therefore flows to the degas tank 12 via the vent line 11. As such, coolant flows to the degas tank even when degas isn't necessarily required -e.g. when the volume of gas suspended in the coolant is low. Moreover, any heated coolant that flows to the degas tank will be replaced by cold coolant from elsewhere in the system. As a result, potentially unnecessary coolant flow through the degas tank slows engine warm-up and can be detrimental to heater performance.

Figures 2A, 2B, 2C and 2D schematically show another previously considered engine cooling system. The system comprises a pump 5 operable to cause coolant to circulate through the engine 6. The engine is provided with an electrical thermostat 17, which in this example is integral with the engine, and which is operable to selectively control the flow of coolant through the return branches of the cooling system, namely: a heater branch 14, a bypass branch 9 and a radiator branch 8. The heater branch is in fluid communication with a heater module 10 which allows the heat from heated coolant which exits the engine to be usefully harnessed for supplying heat to the passenger compartment of a vehicle before being recirculated back to the pump 5 via the bypass branch 9. ln this arrangement the vent fine 11 is connected in permanent fluid communication with the thermostat. As a result, coolant will flow to the degas tank even when, as shown in Figure 2A, the branch lines of the return circuit are all closed e.g. because the engine is cold or below a certain operating temperature.

Figures 2B, 20 and 2D show the operation of the thermostat 17 to selectively open the branches of the return circuit.

As shown in Figure 2B, which represents the engine cooling system opthating above a first threshold temperature which activates the opening of the heater branch line by the thermostat, heated coolant is able to flow to the heater module. It will be appreciated that the flow of coolant to the degas tank, which ultimately cause the replacement of heated coolant by cold coolant from elsewhere in the system, will undermine the performance of the heater module 10.

Figure 2C represents the engine cooling system operating above a second threshold temperature which activates the opening of the bypass line in addition to the heater line so that coolant can flow through both the bypass and the heater branches of the return circuit.

Figure 2D represents the engine cooling system operating when the engine is fully hot, e.g.is above a third threshold temperature which activates the opening of the radiator line branch by the thermostat so that heated coolant can flow via a heat exchanger, or radiator, before being returned to the pump 5. In these circumstances the thermostat also closes the bypass line 9. (It will be appreciated that the Figures are a 2D representation of a 3D apparatus and so the illustrated closing of the bypass line is represented schematically).

Figure 3 shows a combustion engine cooling system according to a first example of the present invention. The system comprises a pump 5 operable to cause coolant to circulate through the engine 6. The engine is connected to a thermostat 7 which operates in a manner similar to the thermostat shown in Figures 1A and 1 B. Thus, the thermostat is operable to selectively control the flow of coolant either through a radiator branch 8 of the system or, alternatively, through a bypass branch 9. The radiator branch and the bypass branch form part of a return circuit of the cooling system. The system also comprises a heater module 10 connected to the engine output circuit such that heated coolant can be suppfled to the heater module and harnessed for providing heat to the passenger compartment of a vehicle before being recirculated back to the pump 5 via the bypass branch 9. A degas branch 11 connects the thermostat to the degas tank and facilitates the flow of heated coolant from the engine to the degas tank 12 where gases are able to separate from the heated coolant.

The engine cooling system also comprises flow control means in the form of a valve 20. The valve is provided on the degas branch 11 and is operable to open/close the degas branch to allow/prevent coolant flow to the degas branch. The valve can be operated independently to the operation of the thermostat 7, which controls the switching of the bypass and radiator circuits, such that the flow of coolant to the degas tank can be separately controlled, independent of engine temperature, based on e.g. an instruction from a control module. The details pertaining to the factors which govern the control of the flow control means will be discussed in more detail below.

Figure 4 shows a combustion engine cooling system according to a second example of the present invention. The system comprises a pump 5 operable to cause coolant to circulate through the engine 6. The engine is provided with an electrical thermostat 17, which in this example is integral with the engine, and which is operable to selectively control the flow of coolant through the return branches of the cooling system, namely: a heater branch 14, a bypass branch 9 and a radiator branch 8. The heater branch is in fluid communication with a heater module 10 which allows the heat from heated coolant which exits the engine to be usefully harnessed for supplying heat to the passenger compartment of a vehicle before being recirculated back to the pump 5 via the bypass branch 9. In this arrangement a degas branch or vent line 11 is connected to the heater branch 14 of the return circuit and allows the flow of coolant to the degas tank 12.

The engine cooling system also comprises flow control means in the form of a valve 21. The valve is provided on the vent line 11 and is operable to open/close the degas branch to allow/prevent coolant flow to the degas branch. The valve can be operated independently to the operation of the thermostat 17 which controls the switching of the heater, bypass and radiator circuits, such that the flow of coolant to the degas tank can be separately controlled based on e.g. an instruction from a control module. The details pertaining to the factors which govern the control of the flow control means will be discussed in more detail below.

Figure 5 shows a combustion engine cooling system according to a third example of the present invention. The system comprises a pump 5 operable to cause coolant to circulate through the engine 6. The engine is provided with an integral, electrical thermostat 17, which is operable to control the opening and closing of the branches of the return circuit of the cooling system. According to the present example the return circuit of the cooling system comprises a heater branch 14, a bypass branch 9, a radiator branch 8 and a degas branch 23. The degas branch 23 is positioned between the bypass branch 9 and the radiator branch. In the present example, the thermostat 17 in conjunction with the switched degas branch line 23 which is operably connected to the thermostat 17, form the flow control means of the present invention.

The thermostat is operable to open/close the branch line 23 in order to allow/prevent the flow of coolant to the degas tank. Optionally, the switching of the degas branch line 23 may be temperature dependent, with the thermostat programmed to open the branch line at a threshold temperature between the threshold temperatures set for the switching of the bypass/radiator branches.

Alternatively, the switching of the degas branch line 23 may be based on a computer generated model of the current or expected gas volume -i.e the volume of gas suspended in the coolant. For example, based on the model of gas volume in the system, the degas branch may be operated to open at certain time intervals, for a certain duration. Alternatively, based on the model of gas volume in the system, the degas branch may be opened as and when it is determined to be required, according to the model. By modelling the gas volume in the system/coolant, it is possible to allow/prevent the flow of coolant to the degas tank based on a more accurate assessment of whether or not degas is required so that detrimental heat loss arising as a result of coolant flow to the degas tank can be alleviated.

The model of gas volume in the system may base may be based primarily on theoretical calculations. Alternatively, the modelling of coolant gas volume may be based on live monitoring of various parameters including engine speed, load and temperature which are then used, e.g. by a computer program, to model the gas production on the basis that the rate of gas production is a function of cylinder pressure and engine speed. Optionally, the model will increment the modelled gas volume when the degas line is closed and decrement the modelled gas volume when the degas line is open for any reason (active degas or for when as a result of other engine requirements).

Alternatively, the determination of current gas volume may be based on a physical measurement. For example, a physical sensor operable to measure coolant gas content may be provided within the cooling system Figure 6 shows a combustion engine cooling system according to a fourth example of the present invention. The system comprises a pump 5 operable to cause coolant to circulate through the engine 6. The engine is provided with an integral, electrical thermostat 17, which is operable to control the opening and closing of the branches of the return circuit of the cooling system. According to the present example the return circuit of the cooling system comprises a heater branch 14, a bypass branch 9, a radiator branch 8 and a degas branch 23. The degas branch 23 is positioned between the bypass branch 9 and the radiator branch. In the present example, the thermostat 17 in conjunction with the switched degas branch line 23 which is operably connected to the thermostat 17, form the flow control means of the present invention.

It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more examples, it is not limited to the disclosed examples and that alternative examples could be constructed without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS1. A cooling system for an internal combustion engine comprising an input for receiving coolant into the engine and a return circuit for returning coolant from the engine to the input, wherein the return circuit comprises a radiator branch and a bypass branch and wherein the return circuit further comprises: i) a degas branch connected to a degas tank; and U) flow control means operable to separately open/close the degas branch to respectively allow/prevent the flow of coolant to the degas tank.
2. A cooling system as claimed in claim 1 or 2, wherein the return circuit comprises a thermostat operable to switch the flow of coolant between the radiator branch and the bypass branch.
3. A cooling system as claimed in any preceding claim, wherein the flow control means comprise a valve provided on the degas branch of the output circuit.
4. A cooling system as claimed in any preceding claim, wherein the return circuit comprises a heater unit which is arranged to receive heated coolant from the engine via a heater branch of the return circuit.
5. A cooling system as claimed in claim 1, wherein the return circuit comprises a thermostat and wherein the degas branch is provided as a switched branch on the thermostat, wherein the thermostat and the switched degas branch form the flow control means.
6. A cooling system as claimed in claim 5, wherein the return circuit comprises a heater unit which is arranged to receive heated coolant from the engine via a heater branch of the return circuit and wherein the degas branch is provided between the heater branch and the bypass branch, or between the bypass branch and the radiator branch.
7. A cooling system as claimed in any preceding claim, wherein the flow control means is operable based on a determination result.
8. A cooling system as claimed in claim 7, wherein the determination result is based on consideration of one or more of: coolant gas volume, temperature and engine requirements.
9. A cooling system as claimed in claim 8, wherein the determination result is at least partly based on coolant gas volume, and wherein the coolant gas volume is obtained from one or more of: theoretical calculations; a computer-generated model of the gas production rate; a physical measure of the gas content of the coolant.
10. A cooling system as claimed in any preceding claim, wherein the flow control means is operable such that the degas branch opens intermittently.
11. A method of cooling a combustion engine comprising an input for receiving coolant into the engine and a return circuit for returning coolant from the engine to the input, wherein the return circuit comprises a radiator branch and a bypass branch, the method comprising operating flow control means in order to independently open/close a degas branch of the return circuit in order to allow/prevent the flow of coolant to a degas tank.
12. A method of cooling a combustion engine as claimed in claim 11, wherein the step of operating the flow control means comprises obtaining a determination result based on consideration of the current/expected coolant gas volume.
13. A cooling system fora combustion engine having, the cooling system comprising a degas branch connected to a degas tank, wherein the cooling system comprises flow control means operable to open/close the degas branch independently of engine temperature.
14. A cooling system or method substantially as herein before described with reference to the accompanying drawings.