Cooling system for engine

A transversely disposed water cooled internal combustion engine for a motor vehicle that cooperates with a heat exchanger that is disposed transversely to the engine compartment and in parallel relationship with the engine. A cooling pump and thermostat assembly is mounted on the side of the engine between its ends and facing the heat exchanger for communicating the heat exchanger with the engine cooling jacket. Coolant is delivered first to the cylinder head and then through the cylinder head to the cylinder block cooling jacket. The coolant pump is driven off to an intermediate shaft driven by the timing mechanism for driving the camshafts of the engine.

BACKGROUND OF THE INVENTION 
This invention relates to a cooling system for an engine and more 
particularly to an improved cooling system of the type wherein the 
cylinders of the engine are parallel with the associated heat exchanger 
for the engine. 
In many types of motor vehicles, the engine is placed transversely in the 
engine compartment and closely adjacent the axles which it drives. 
Normally this means that the cylinders are parallel with the associated 
heat exchanger which may be positioned either ahead of or to the rear of 
the engine within the engine compartment. Conventionally engines are 
provided with a cooling system wherein water is introduced to the engine 
at one end of the engine and discharged from the opposite end of the 
engine. This tends to give rise to uneven temperatures in the engine from 
one end to the other. That is, the cylinders disposed closer to the water 
inlet will operate at a lower temperature than those disposed remotely 
from the water inlet and adjacent the water outlet. Also, in conjunction 
with transverse placement of the engine, there are certain difficulties in 
connection with transferring the coolant between the engine and the heat 
exchanger. 
It is, therefore, a principal object of this invention to provide an 
improved cooling system for an engine wherein the temperature of the 
cylinders will be more uniform. 
It is a further object of this invention to provide an improved cooling 
system arrangement for an engine which is disposed so that it extends 
parallel to the associated heat exchanger. 
It is a further object of this invention to provide an improved cooling 
system for an engine wherein the engine has its water delivery and water 
exit ports between the ends of the engine. 
In many forms of engine cooling systems, the coolant is delivered to the 
engine first to the cylinder block and then to the cylinder head. Of 
course, the cylinder head is the more highly heated area. This type of 
arrangement may not provide adequate cooling for the cylinder head. Also, 
it is the normal practice to mount: the water pump relatively low in the 
cylinder block and this further makes it difficult to introduce coolant 
first to the cylinder head rather than to the cylinder block. 
It is, therefore, a still further object of this invention to provide an 
improved cooling system for an engine wherein the water pump can be 
positioned more closely to the cylinder head so as to facilitate delivery 
of the cooling water to the cylinder head before the cylinder block. 
SUMMARY OF THE INVENTION 
A first feature of this invention is adapted to be embodied in a cooling 
system for an internal combustion engine having a plurality of aligned 
cylinders. A heat exchanger is disposed in parallel relationship to the 
engine. The engine has a cooling jacket and a water pump is disposed 
between the ends of the engine and on the side adjacent the heat exchanger 
for circulating coolant through the engine cooling jacket and through the 
heat exchanger. 
Another feature of the invention is also adapted to be embodied in a 
cooling system for an internal combustion engine that has a plurality of 
aligned cylinders and a heat exchanger disposed parallel to the engine. A 
cooling jacket is provided for the engine and a thermostatic valve is 
provided in conduitry that connects the cooling jacket with the heat 
exchanger for controlling the temperature of the cooling jacket. In 
accordance with this feature of the invention, the thermostat is 
positioned between the ends of the engine and on the side adjacent the 
heat exchanger. 
Yet another feature of this invention is adapted to be embodied in a 
cooling system for an internal combustion engine having a cylinder block, 
a cylinder head and an overhead camshaft mounted in the cylinder head. A 
camshaft drive arrangement is provided for driving the camshaft from the 
engine output shaft. This includes a plurality of shafts that are 
journaled for rotation about axes parallel to the engine output shaft axis 
and the camshaft axis. In accordance with this feature of the invention, a 
water pump for circulating coolant through the engine cooling jacket is 
driven from one of these intermediate shafts which intermediate shaft is 
disposed in proximity to the cylinder head and above the lower end of the 
cylinder block.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
Referring first in detail to FIGS. 1 and 2, a motor vehicle powered by an 
engine construction in accordance with an embodiment of the invention is 
shown primarily in phantom and is identified generally by the reference 
numeral 11. Only the portion of the motor vehicle 11 associated with the 
engine compartment has been illustrated because the invention deals with 
the engine construction and its placement in this engine compartment and 
the cooling system therefor. 
In the illustrated embodiment, the vehicle 11 is of the front engine 
transversely disposed front wheel drive type and has an engine compartment 
12 that extends transversely across the front of the motor vehicle 11 and 
which is positioned rearwardly of an air inlet opening 13 which is formed 
in the body of the vehicle forwardly of the engine compartment 12. A pair 
front wheels 14 are suspended by the chassis of the vehicle 11 in a known 
manner and have associated with them axle shafts 15 which are driven in a 
manner to be described. 
A power unit, indicated generally by the reference numeral 16 and which is 
comprised of an internal combustion engine, a change speed transmission, 
and a final drive, is positioned transversely in the engine compartment 12 
for driving the axle shafts 15. Basically, the power unit 16 has a 
construction as described in the copending application entitled "Engine 
Unit For Vehicle", Ser. No. 270,357, filed Nov. 14, 1988, and assigned to 
the Assignee hereof, and specifically the embodiment of FIGS. 6 through 8 
thereof. Because of the basic similarity of the engine of this embodiment 
to that embodiment of Ser. No. 270,357, certain components have not been 
illustrated fully, nor will they be described in full detail. Where that 
is the case, reference may be had to the aforenoted copending application, 
the disclosure of which is incorporated herein by reference. 
A radiator 17 of the cross flow type is positioned transversely in the 
engine compartment 12 directly behind the air inlet opening 13. As a cross 
flow radiator, the radiator 17 has header tanks 18 and 19 disposed at its 
opposite sides which receive coolant from the power unit 16 through a hose 
21 and which return coolant to the power unit 16 through a hose 22. Other 
components of the cooling system will be described hereinafter. 
The engine portion of the power unit 16 includes a cylinder block 23 that 
is provided with a plurality of aligned cylinder bores in which pistons 24 
reciprocate. The cylinder bores in which the pistons 24 reciprocate are 
inclined from the vertical rearwardly away from the engine compartment air 
inlet opening 13 along a line L1 as best seen in FIG. 5. In the 
illustrated embodiment, the engine has six cylinders although is to be 
understood that the invention can be practiced with engines having other 
numbers of cylinders. The pistons 24 are connected by means of connecting 
rods 25 for driving a crankshaft 26 that is rotatable about an axis that 
lies on the line L1 and which is disposed at the lower ends of the 
cylinders. The crankshaft 26 is rotatably journaled in a known manner. 
A first crankcase portion 27 is affixed to the cylinder block 23 at its 
lower end. However, because of the angular disposition of the cylinder 
block 23, the crankcase portion 27 extends generally vertically along a 
line that is disposed at an acute angle to the vertical but which extends 
forwardly of a vertically extending plane from the line L1. This plane is 
generally designated by the line L2 and lies at an acute angle to the 
plane L2. A further crankcase portion 28 is affixed to the portion 27 and 
also extends vertically upward and is disposed forwardly of the crankcase 
portion 27. The portions 27 and 28 and the cylinder block 23 define a 
crankcase chamber 29 in which the crankshaft 26 rotates. 
As may be seen in FIGS. 7 and 8, one of the cheeks of the crankshaft 26 is 
formed with an integral gear portion 29 which is enmeshed with a gear 31 
that is affixed to or associated with an accessory or output shaft 32. The 
accessory or output shaft 32 is supported for rotation by the cylinder 
block 23 and crankcase portion 27 for rotation about an axis that is 
disposed parallel to the axis of rotation of the crankshaft 26 and the 
axle shafts 15, but which lies on the line L2. The line L2 is disposed at 
an acute angle, as aforenoted, to a vertically extending plane and at an 
acute angle .alpha. relative to the plane L1. This acute angle 
relationship permits a very compact engine, accessory and final drive 
assembly, as will become apparent. 
With the prior art type of constructions and specifically that shown in 
aforenoted application Ser. No. 270,257, the output shaft axis 32 is 
disposed forwardly and at least at a right angle to the cylinder bore axis 
defined by the line L1. As a result, this axis is disposed at a relatively 
low height from the vertical and forwardly of the crankshaft axis. 
However, by disposing the output shaft angle 32 at an acute angle to the 
plane L1, the height is raised but the horizontal length of the engine is 
substantially reduced. As a result and as will be described, this permits 
a more compact assembly. 
A flywheel, indicated generally by the reference numeral 33 and having a 
starter gear 34 is affixed for rotation with the output shaft 32. The 
flywheel 33 is associated with a clutch (not shown) as described in 
aforenoted application Ser. No. 270,357 for driving a primary shaft of a 
change speed transmission, indicated generally by the reference numeral 
35. The change speed transmission 35 includes a secondary shaft 36 and a 
plurality of intermeshing gear sets. 
The gear sets are contained on the transmission primary shaft and secondary 
shaft 36 for driving the secondary shaft 36 from the primary shaft at 
selected speed ratios. The secondary shaft 36 drives an input gear 37 of a 
differential assembly for driving the axle shafts 15 in a well known 
manner. 
It should be noted that the acute angle between the lines L1 and L2 and the 
close positioning of the transmission secondary shaft 36 to the line L1 
permits a very compact final drive assembly and keeps the distance between 
the primary shaft of the transmission 35 and the axis of rotation of the 
axle shafts 15 very close to each other. The close positioning of the 
output shaft axis and the axles 15 also makes it possible to use smaller 
diameter gears for the final drive and this further adds to the 
compactness of the assembly. A transmission casing cover 38 encloses the 
portion of the transmission which has been described for driving the axle 
shafts 15. This cover 38 is affixed to the cylinder block 23 and crankcase 
portions 27 and 28 in a suitable manner. 
A cylinder head 39 is affixed in a known manner to the upper end of the 
cylinder block 23 and closes the cylinder bores in which the pistons 24 
reciprocate. Overhead mounted intake and exhaust valves, as described in 
copending application Ser. No. 270,357, are mounted in the cylinder head 
39 for controlling the admission of an intake charge and the exhaust of 
the burnt charge. These valves are operated by means of an intake camshaft 
41 and an exhaust camshaft 42 that are journaled on the cylinder head 
assembly 39 and which are enclosed within a cam chamber closed by a cam 
cover 43. The camshafts 41 and 42 have respective cam lobes 44 and 45 for 
operating the intake and exhaust valves in the manner described in the 
aforenoted copending patent application. 
A camshaft drive sprocket 46 (FIGS. 5, 7 and 8) is formed integrally on the 
accessory or output shaft 32 and drives a first timing chain 47. The first 
timing chain 47, in turn, drives a sprocket 48 that is affixed to an 
intermediate cam drive shaft 49. The cam drive shaft 49 is journaled in an 
appropriate manner on the cylinder head 39 and, in turn, drives a second 
sprocket 51. A second chain 52 drives a pair of driven sprockets 53 and 54 
that are affixed to the camshafts 41 and 42 respectively for driving these 
camshafts. As noted in the aforenoted copending application, the two to 
one speed reduction between the crankshaft 26 and camshafts 41 and 42 may 
be achieved in stages through the camshaft drive mechanism as 
aforedescribed. Because this mechanism is described in more detail in the 
copending application, further description of it in this application is 
not believed to be necessary. 
The intake valves, as aforedescribed,.are associated with an air induction 
system that includes a plenum chamber 55 that extends transversely across 
the engine compartment 12 forwardly of the cylinder head and cylinder 
block 23. The plenum chamber 55 is provided with an air inlet portion 56 
in which a throttle valve 57 (FIGS. 1 through 4) is positioned for 
controlling the engine speed. Air is delivered to the inlet section 56 
from a remotely positioned air cleaner and silencer assembly (not shown). 
The plenum chamber 55 has either affixed to it or formed integrally with it 
a plurality of runners 58 that cooperate with manifold pipes 59 which 
serve the individual cylinders of the engine and specifically the intake 
ports 60 of the cylinder head 39 in a known manner. 
Spark plugs 61 (FIG. 13) are contained within spark plug pockets 61 formed 
in the cam cover 43 and are in turn threaded into the cylinder head 39 for 
firing the charge admitted to the combustion chambers of the engine. The 
ignition system for firing these spark plugs may be of any known type. The 
burnt exhaust gases are then discharged through the exhaust ports 70 of 
the cylinder head 39 to an exhaust manifold, shown partially and indicated 
by the reference numeral 62. 
The engine is provided with a dry sump lubrication system that includes a 
dry sump lubricant reservoir 62 that is supported from the crankcase 
member 28 and which extends forwardly of the engine and vertically 
upwardly in the area to the rear of the air inlet opening 13 to the engine 
compartment 12. The top of the reservoir 62 has a filler neck 63 to which 
a detachable cap 64 is attached. The tank 62 has a large internal volume 
65 and the filler neck 63 and a portion of the volume 65 extends upwardly 
beyond the axis of rotation of the engine output shaft 32. As a result, 
the tank 62 has a large surface area that will be exposed to the cooling 
air flow. This will insure that the lubricant is well cooled. The greater 
height and larger volume for the dry sump lubricant reservoir 62 is made 
possible because of the acute angle relationship between the planes L1 and 
L2 which has been previously discussed. This permits the tank 62 to be 
positioned rearwardly in the engine compartment and can have a significant 
height without adversely effecting the hood line of the vehicle. 
A lubricant pressure pump 7I (FIGS. 5 through 7) of the tricodal type is 
driven by the accessory shaft 32 and draws oil from the lower portion of 
the tank 62 through a strainer inlet 66. A conduit 67 extends from the 
strainer inlet 66 to the inlet side of the pressure pump 71. Lubricant is 
then delivered from the pressure pump 71 to an oil filter 68 that is 
mounted on the front of the crankcase casing 28 with an oil cooler 69 
being interposed between it and the crankcase member 28. The oil cooler 69 
receives coolant from the cooling system including the radiator 17 in a 
manner to be described. The lubricant is then delivered to the various 
components of the engine for their lubrication in a suitable manner with a 
portion of the flow path being shown by the arrows in FIG. 6. 
The lubricant will then return to the crankcase chamber 29 by gravity flow 
and specifically to an area 72 positioned below a baffle plate 73. The 
baffle plate 73 is juxtaposed to the crankshaft 26 so as to control the 
oil flow in this area. The oil will then drain to a well 74 formed below a 
screen 75. This oil is then picked u by the inlet 76 of a scavenge line 77 
that is formed in the crankcase portion 28 for delivery to a pair of 
scavenge pump assemblies 78. The scavenge pump assemblies 78 are driven 
from the accessory shaft 32 and are also of the tricodal type. The 
scavenged oil is then returned to the dry sump tank 62 through a return 
conduit 79. The dry sump tank 62 is provided with a baffled breather 
system (not shown) for venting purposes. 
An accessory drive pulley 81 is affixed to the end of the accessory or 
output shaft 32 opposite to the flywheel 33 and drives a belt 82. The belt 
82 drives a plurality of accessories such as an alternator 83, power 
steering pump 84 and air conditioning compressor 85. As may be seen from 
FIG. 7, the accessory drive pulley 81 is affixed to the accessory drive 
shaft 32 at a point that is inwardly of the adjacent bearing end 86 of the 
crankshaft 26 which bearing end is supported in a boss 87 of the cylinder 
block 23 and crankcase. 
There is provided a recess 88 adjacent this area so as to permit the 
accessory drive shaft 32 to rotate about an axis that is disposed at a 
very close distance to the axis of rotation of the crankshaft 26. This 
arrangement also insures that the engine will have a short overall length 
and that the accessories which are mounted externally of the engine are 
disposed between its ends to provide a compact assembly. However, due to 
the angular disposition of the cylinder block 23 and the bores therein, 
these accessories are readily available for servicing. 
It should be noted that the portion of the output or accessory shaft 32 
that is driven by the crankshaft 26 and which drives the camshaft 
mechanism is disposed internally of the body of the engine and 
specifically of the cylinder block 23. However, the portion of the shaft 
32 which drives the pulley 81 and pumps 71 and 78 is external of this 
body. 
In conjunction with the ignition system for the engine, a timer disk or 
wheel 92 (FIGS. 3 and 7) is affixed to the end of the crankshaft 26 
adjacent the accessory drive pulley 81 and carries a marker 93 that 
cooperates with a fixed pulser coil 94 so as to provide an indication of 
crankshaft rotation. 
It has already been noted that the engine 16 is of the liquid cooled type 
and embodies a cross flow radiator 17 that is disposed transversely in the 
engine compartment and, accordingly, which extends parallel to the length 
of the engine. In this regard, although the engine 16 is disposed 
transversely in the engine compartment 12, the end of the engine which 
supports the camshaft drive is considered to be the front of the engine 
and the opposite end is the rear of the engine. The side of the engine 
facing the inlet opening 13 is considered as the front side whereas the 
remaining side is considered the rear side. As already noted, the front 
side of the engine is the intake side and the rear side is the exhaust 
side. 
The coolant is circulated through the radiator 17 and cooling jackets of 
the engine (as will be described) by a water pump assembly, indicated 
generally by the reference numeral 95 and shown in most detail in FIGS. 8 
through 15, although the construction is shown in other figures 
additionally. The water pump assembly 95 includes an impeller 96 that is 
contained within a pumping cavity 97 formed in part by a cover plate 98 
that is affixed to a side of the cylinder block 23 adjacent a coolant 
cavity 99 formed therein. The water pump outlet from the pumping cavity 97 
communicates with the cavity 99 through a delivery conduit 101. 
An impeller 96 is affixed for rotation with a pump drive shaft 10 that is 
journaled in the cylinder block 23 by means of spaced bearings 103. An 
idler sprocket 104 is affixed to the shaft 102 and is engaged with the 
camshaft drive chain 47 on its return side. As may readily be seen from 
FIG. 5, this positioning of the pump shaft 102 permits a very compact 
assembly and, at the same time, permits the water pump assembly 95 to be 
disposed in close proximity to the cylinder head 39. This is important 
because, in accordance with a feature of the invention, the cooling water 
is delivered first to the cylinder head cooling jacket before the cylinder 
block cooling jacket so as to effect more rapid cooling of the more highly 
heated combustion chamber areas. 
It should be noted that the chain 47 is disposed so that the sprocket 104 
and sprocket 48 for the intermediate camshaft drive shaft 49 lie in a 
recess formed between the intake ports 60 of the first and second 
cylinders, indicated schematically at X1 and X2 as may be seen in FIG. 3. 
This permits a further compaction of the overall construction without 
adversely effecting servicing of the components. It should be noted that 
the cylinder block 23 is provided with a recess 105, which has been 
previously referred to, in which the chain 47 is positioned. This recess 
105 cooperates with a corresponding recess 106 formed in the cylinder head 
39, the rear end of which recess is closed by a closure plate 107. 
Although the configuration is described as being between the first and 
second cylinders X1 and X2, it is to be understood that the water pump 
assembly can be positioned anywhere along the front side of the engine. 
However, there are advantages to putting it closer to the front end of the 
engine so as to minimize the shaft length and keep the assembly more 
compact. 
As has been noted, it is desirable to introduce the cooling water from the 
water pump 95 first to the cylinder head cooling jacket rather than to the 
cylinder block cooling jacket. Although the water pump 95 outputs coolant 
to the cylinder block pocket 99, this pocket does not communicate directly 
with the cooling jacket of the cylinder block, which will be described 
later. Rather, the pocket 99 has a discharge port 108 on its upper face 
(FIG. 11) which communicates directly with a corresponding inlet port 109 
formed in a lower face of the cylinder head 39. As may be best seen in 
FIG. 12 and 13, the cylinder head is provided with a longitudinally 
extending main gallery 111 that extends along the front or the intake side 
of the cylinder head 39 and which communicates with the inlet opening 109 
through a delivery passage 112 that is formed in an embossment of the 
cylinder head adjacent the second cylinder. 
Continuing to refer to these figures, a plurality of hold down studs or 
bolts 113 extend through bosses 114 formed in the cylinder head assembly 
for affixing the cylinder head to the cylinder block. The bosses 114 
define a plurality of openings that register around the intake ports 60 of 
the individual cylinders for delivering coolant first to these intake 
ports so as to insure that they are well cooled and to increase the 
volumetric efficiency of the engine. It should be noted that the spark 
plugs 61 are positioned in a nested fashion between the intake ports 60 so 
as to insure good cooling of the spark plugs. In the illustrated 
embodiment, the engine is provided with three intake valves for each 
cylinder. These intake valves each have individual ports 60 that cooperate 
with a single intake opening in the side of the cylinder head as shown in 
FIG. 11 so that these ports are, in effect, siamese. 
After the cooling water has passed around the intake ports 60, it will 
encounter flow dividers 115 that are positioned between the intake ports 
of the respective cylinders and the exhaust ports 70 thereof. These flow 
dividers have large protuberances 116 which are spaced a distance Z in a 
transverse direction from the spark plugs 61 so as to insure good cooling 
of the spark plugs. The cooling water then cools the exhaust ports 70. The 
cylinder head cooling jacket outside of the main gallery 111 is identified 
generally by the reference numeral 117 and as may be seen in the Figures, 
provides adequate cooling for the cylinder head with water which has not 
been preheated because of its flow through the cylinder block. 
The lower surface of the cylinder head 39 is provided with a pair of 
downwardly facing coolant discharge ports 118 which are disposed in pairs 
on opposite sides of the cylinder head 39 and between adjacent cylinders. 
These passageways 118 cooperate with corresponding passageways 119 formed 
in the upper deck of the cylinder block 23 (FIGS. 6 and 9) so as to 
deliver coolant to the cylinder block cooling jacket 121 which generally 
extends around the individual cylinder bores. As may be best seen in FIG. 
9, the cylinder block cooling jacket 121 does not extend around the full 
circumference of the cylinder bores. This is so as to permit a more 
compact construction for the cylinder block and does not adversely effect 
its cooling. 
The cylinder block cooling jacket 121 has an outlet opening to which a 
water discharge fitting 122 (FIGS. 4, 6, 11 and 15) is affixed. The water 
outlet fitting 122 may be formed as part of a housing assembly that 
includes the housing assembly for the water pump 95 so as to facilitate 
ease of construction. The cylinder block cooling outlet is indicated at 
123 in FIG. 11, wherein the fitting 122 is shown in phantom. The housing 
in which the fitting 122 is formed, is provided with a bypass passageway 
124 that extends to a thermostat housing assembly 125. This housing 
assembly may also be formed from the same housing as the water pump and 
the outlet fitting 122 but preferably has a separable cap section 126 so 
as to permit insertion and removal of a thermostatic valve assembly, 
indicated generally by the reference numeral 127. The thermostatic valve 
assembly 127 has a caging portion 128 that is affixed between the main 
housing 125 and the discharge fitting 126. 
It should be noted that cooling water enters the thermostat housing 125 in 
a direction perpendicular to the radiator 17 and cylinder block and then 
turns through 90.degree. for entry into the water pump 95. This provides a 
relatively compact and yet effective cooling system flow pattern. 
The entire cooling system and its flow path will now be described by 
particular reference to FIG. 15. As has been previously noted, the outlet 
header tank 19 of the cross flow radiator 17 communicates with a hose 122 
that is fixed to the thermostat housing cover 125 so as to deliver water 
to the engine. When the engine is at its operating temperature, as 
indicated in FIG. 15, the thermostatic valve 127 will be open and the 
bypass passageway 124 Will be closed. The water pump 95 will then deliver 
water initially into the pocket 99 of the cylinder block 23 and then 
immediately be transferred to the cylinder head through the opening 109 
for circulation through the cylinder head cooling jacket 117. This coolant 
is then returned to the cylinder block cooling jacket 121 through the 
passageways 118. The coolant can then return to the radiator through the 
outlet fitting 122 and hose 21 so as to enter the inlet header tank 18. 
Before the engine has been heated, the thermostatic valve 127 will move so 
as to open the bypass passageway 124 and preclude coolant from entering 
the cooling jacket from the radiator 17. The flow of coolant will be then 
again through the cylinder head cooling jacket 117, cylinder block cooling 
jacket 121 and returned to the water pump through the bypass passageway 
124. 
It should be noted that the cylinder head cooling jacket 117 is provided 
with an outlet opening 131 in its front face that coacts with a conduit 
132 for delivering coolant to the oil cooler 69. This coolant is then 
returned through a return conduit 133. As a result, coolant will always be 
circulated through the oil cooler 69 even when the thermostatic valve 127 
is closed. This will not only provide for heating of the oil initially to 
operating temperature, but will also prevent air from being collected in 
the water jacket of the cylinder head. There is also provided a heater 134 
for the associated vehicle and the cylinder head 39 is provided with an 
outlet duct 135 for supplying heated water to the heater 134 through a 
hose 136. This coolant is returned through a return hose 137. 
The system may also include a water temperature sensor 138, a water 
temperature sensor 139 and a sensor 141 positioned in the header tank 18 
for controlling a thermostatically operated fan. Of course, the location 
of the various conduits and outlets can be varied but the described 
construction is particularly effective in providing effective cooling and 
also the purging of air from the system. It is also to be understood that 
the foregoing description is that of a preferred embodiment of the 
invention, and that various changes and modifications may be made without 
departing from the spirit and scope of the invention, as defined by the 
appended claims.