FSJ Radiators and Cooling
By by Joe Guilbeau
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This article is a three part series addressing AMC Full Size Jeeps
cooling basics and system design, some key diagnostic troubleshooting
tips and two
different design philosophies that illustrate how the available
the aftermarket can be utilized to achieve your cooling goals.
Radiators and cooling should be at the forefront of your maintenance
upgrade schedules for your Full Size Jeep. We will document several of
myriad design and equipment choices for solving overheating issues and
primarily address the eight-cylinder engines, although the overall
hold true for the six-cylinder mills as well.
Part 1 of this article
addresses the basic system configuration of an OEM 5.9 Liter AMC-360 as
comes from the factory. After a brief synopsis of the cooling system
components, we will touch on diagnostic and troubleshooting of cooling
Part 2 of this article details
a system that I am currently running on my 1983 Cherokee Laredo and has
itself from here in Texas to Arizona and back in 115° F heat, crawling
Lemon outside of Tucson or in the Big Bend National Park.
Part 3 of this article
details another system design using an Aluminum radiator and an
that is a turnkey solution to your cooling requirements.
It is a sad, but true fact that the cooling systems in our Jeeps are
probably the most neglected and least maintained system in our Jeeps,
yet it is
relatively simple to comprehend and probably the easiest to
some basic knowledge.
Part One: Basic System Configuration and Diagnostic
Our Jeep cooling systems are designed to allow the engine to reach a
operating temperature as soon as possible and then maintain that
temperature over the course of driving in a wide range of ambient
ranges and finally, to prevent any overheating that might occur.
the closed loop system are designed to absorb engine heat and transfer
the radiator so that through convection and thermodynamics heat
The below illustration depicts the components of an OEM 5.9 Liter
Jeep engine of the mid-80's.
The centrifugal water pump impeller blades, at the center of the
cover, into both left and right banks of the cylinder block areas
the coolant. The water jackets there route the coolant around all of
cylinders, up through some holes in the cylinder block area, and then
cylinder heads through additional water jackets. There additional heat
transferred to the coolant by the exhaust valves. It continues to flow
the front of the cylinder heads into the intake manifold and to the
The right cylinder head (passenger side) routes the coolant to the
manifold water jacket to an outlet at the upper rear of the intake
which is the inlet hose for coolant flow through the heater core. If
inside the cab are adjusted to open the heater valve, coolant is routed
the heater core. If the heater valve is closed, the coolant is routed
the intake manifold to a bypass hose back to a fitting on the water
in turn, is pressurized via the impeller blades.
This continues until the thermostat reaches its set point and begins
up, allowing coolant that has been trapped in the closed loop system to
the radiator intake inlet at the top of the radiator tank, which is fed
radiator hose connected to the thermostat housing. Before the
reaches its set point and opens, coolant flows through a bypass hose
routes it from the thermostat housing to the top of the water pump.
the blocks heated coolant to circulate so as not to create hot spots in
Once the thermostat begins to open, the impeller blades of the water
force coolant to flow through the radiators cooling tubes and out of
radiator outflow outlet to the intake of the water pump via the lower
hose. This hose should be stiff or reinforced so that it does not
wire enforced, inspect yearly to insure that the wire inside the
is rust free.
Coolant passing through the radiator is cooled by air passing over
and fins of the copper/aluminum radiator and is assisted by the
and the vehicles forward motion. Some radiators are equipped with
transmissions tubes, and the coolant inside these radiators will pick
additional heat loads from this source. After the coolant reaches the
pump, the impeller blades continue to pressurize the water to force it
another circulation cycle, and as the thermostat continues to open, the
reaches a maximum flow rate which is determined by the passage rate of
coolant through the block passages, the heater core (if open) the
and the amount of coolant that the impeller blades of the water pump
can move through
all of these restricted water passages, least of which are the radiator
In addition, the heated coolant will begin to expand and further
the closed loop system. Most systems allow this pressure to be bled off
radiator pressure relief cap rated in the neighborhood of 12-15 lbs. of
pressure. There is a coolant recovery tank that collects this overflow
condition. For every lb. of pressure exerted on water, the boiling
is raised by 3°F. Normal sea level temperature for water to begin to
boil is 212°F,
so with a 15 lb. radiator cap installed, the water temperature inside
engine block can reach a temperature of 257° F, before it begins
So, a strong word of caution is needed here, as this is a very
level of pressurized water that is far past the boiling point, and may
well become pressurized steam in less maintained systems. Needless to
this is very dangerous to come in contact with. So be very, very
otherwise skin grafts and many months of recovery will almost bring you
where you were before any mishap scalded you.
Here is a quick experiment so that the reader can visualize the
principals of Nucleate Heat Transfer, where the water passages near the
manifolds and exhaust valve surface areas get hot enough so that
Boiling will take place. Essentially, bubbles form at the surface of
metals, and are then swept downstream where they condense in the
To illustrate this concept, take a pot and put some tap water in it.
pot on the stove and bring up the heat until steam bubbles begin to
form on the
bottom of the pot. Keep the heat steady, so that a pretty good steady
very small bubbles are forming on the bottom surface of the pot while
the pot not nearly at a full boil.
This will approximate the exhaust water-cooling passages on the AMC
and is a pretty good illustrative concept of Nucleate Boiling. Grab a
and stir the water so that it flows in a circular clockwise or
rotation very, very slowly.
As you begin to increase the speed of the circular rotation of the
water, you will notice some trends with experimentation of the
of the fluid. A faster circulation prevents steam bubbles from forming,
slower circulation results in increased steam bubble formation. This is
Nucleate Boiling on the surface of the pot.
Some conclusions should be forming, namely that increasing the flow
water over the surface of the bottom of the pot in contact with the gas
or electric heating element inhibits steam bubbles from forming.
This is important for quite a few reasons, namely that once steam
begin to form, they isolate the metal surface from contact with the
After all there is a steam pocket (bubble) that is forming. This bubble
in less cooling fluid being in contact with the metal, which in turn
hotter. Water as strange as it may seem, is a better heat transfer
steam. The steam bubbles actually form an insulating barrier to prevent
appropriate heat transfer to the liquid coolant and thus the metal
even hotter, and in turn the coolant eventually gets hotter and perhaps
to boil and steam.
Well, this is all very well and good, but how to apply this
assist in the goal of improving the cooling systems of our Jeeps, is
are really interested in.
The single most important thing to understand about radiators and
that additional radiator surface area will give more Return on
than any other possible modification. So get the largest square inches
surface area possible for your next radiator and stuff it into your
The Jeeps cooling system is designed to operate in a closed loop
with the centrifugal water pumps impeller blades being fed by the lower
of the radiator. The water pump sends the water flowing through the
water jackets cast into the block help cool the cylinders and exhaust
generated heat. The head gaskets seal the cylinder heads to the engine
and the coolant is forced into the cylinder heads where it cools off
exhaust ports/valves and combustion chambers. The coolant is then
the intake manifold and into the heater core or the bypass thermostat
the thermostat housing, or thru the thermostat when open.
When the engine is cold, the thermostat is not open, and the
housing includes a bypass hose that sends the heated coolant (which has
reached the set point of the thermostat) back into the centrifugal
to be re-circulated. Once your coolant absorbs enough heat, it reaches
thermostat set point temperature, and the thermostat begins to open.
coolant is now routed through the thermostat to the upper radiator
bypass hose will continue to route some coolant directly to the water
The upper radiator hose sends whatever coolant the thermostat and
can manage to deliver to the inlet of the radiator, which acts as a
exchanger to transfer excessive heat to the atmosphere, through the
ambient air flowing through the radiator cooling fins, by either the
pulling ambient air through the radiator or the passage of air as the
is in forward motion.
With this basic cursory understanding of the cooling operation in
we can now move on to some specific diagnostic routines that should be
for improving the performance of the cooling system.
Now we can move on to the subject of diagnosing cooling issues.
We need to get some data that is empirical and repeatable, and
some instruments are required in order to measure and not guesstimate
that we will be using to form a plan of action. Infrared hand held
meters are really great and costly! Sears has multimeters with
included for about $65-dollars. Just clamp in a couple of thermocouples
the radiator hoses and plug the meter into the thermocouple that you
measurements from. Pretty simple, eh?
We should be measuring the data that is most responsible for the
our Jeeps, the radiator. So, with thermocouples, one on the inlet tube
top of the radiator and one on the outlet tube on the lower end of the
will give us the data that we require.
When the inlet temperature is generally around 190°F and the return
temperature is 165-175°F or lower, depending upon ambient air
then we can pretty much agree that the rig is operating per the design
parameters that were set by the good folks at AMC at the beginning of
When the inlet temperature is about 220°, and the outlet
temperature is pretty low, we can easily theorize that very little
flowing through the radiator, but what IS flowing through is being
its heat per design parameters, otherwise the outlet temperature of the
radiator would be raised substantially, right?
So, some possibilities are the thermostat is not opening fully, to
heated block water to transition to the radiator or the water pump
blades are no longer operating at peak performance and there is not
coolant flowing through the radiator. This is bad, and fairly easy to
troubleshoot. The hoses on the vehicle will give some indication, the
is extremely hot, and the lower hose is not near as hot, but does not
be full of coolant and it is feeling rather soft. This indicates that
enough water is being returned to the block, causing the lower radiator
collapse in some cases. This is a good time to remind all that a good
lower radiator hose is imperative with a higher flowing water pump.
Now, if the inlet temperature or the temperature gauge is spiking
down when the engine rpm's pick up (as a recent posts have suggested),
have a condition that leads me to believe that excessive heat is being
generated, and when the engine rpm's pick up, the heat spike is rapidly
This would seem to indicate that revving the engine has some
effects. If the temperature change were immediate, then we would
low coolant levels or low pressure in the system is allowing heated
form and influence the temperature sender. There might be a possible
the system, so when the vehicle is stopped and the hood is opened while
engine is still running, one may carefully release the pressure on the
cap, no sudden pressure release and you have found your problem, most
worn out radiator cap.
Since the coolant level is not at the desired level or pressure,
form and be trapped at the top portion of the closed loop system,
the thermostat housing and hose area along with the top portion of the
radiator, all of these areas will be super hot. This will degrade the
the radiator cap and test the integrity of the radiator. Your
senders are also located in this general area as well.
OK, another situation might be that the inlet temperature is high
again, 220°F or
so, and the outlet temperature is also very high. So we might suspect
heat transfer of the coolant is not keeping up with the demands of the
The coolant is hot going in and hot going out of the radiator. What
this to happen can be one of several scenarios.
One is that the radiator must be capable of handling the heat load,
go back to the basic design theory that 1 square inch of radiator
is needed for every cubic inch of engine, with at least a 20% overhead,
translates to at least a 25-inch wide radiator with 17 inches height
with the right design parameters of 3 to 4 cores with the right amount
per linear inch. Also, the extra rows increase the volume of coolant
thus aiding in cooling, as the more coolant there is to conduct the
the greater the chance of lowering the overall intake temp back to the
pump. Another benefit of adding rows is that increased fin area is
further assisting the heat transfer process. Finally, the added tubes
for additional flow, thus increasing the flow rate of the coolant thru
closed loop system.
Two, there must be enough coolant flow to circulate through the
order to transfer enough heat to keep up with the heat load. As long as
the high output water pumps and the high flow thermostats, this
probably can be
ignored; we must however insure that the radiator is not crudded up
Three might be that we have enough radiator and enough coolant and
coolant is flowing efficiently enough to keep up with the heat loads,
is not enough air flow across the radiator to scrub sufficient heat to
with the heat load.
Speaking of radiators, most of ours are older than 20 years; the
made of stuff about 0.010 of an inch thick. These dinosaurs are held
by acid core solder, just how tuff do you think this stuff is?
How about when the engine overheats and we turn on the Heater/Fan to
in cooling. If this works you have increased the cooling fin surface
the radiator and you have increased the airflow across those fins in
core, while simultaneously increasing the total amount of coolant
Now, here is where some folks join in the fray with Heavy Duty Fan
and Flex Fans and such. Kind of makes you wonder if enough
given to the other areas of the closed loop system.
That this solution has worked for so many is a testimony to the fact
the closed loop system probably worked when the vehicle was new, but
twenty to thirty years old and bored over as most of our rigs are,
bound to crop up. Also consider the fact that the radiators most of us
using are probably not nearly new with some blocked passages, and the
pumps have impeller blades eaten by cavitations. That thermostat we
just put in
last year was a bargain for $3.87 at the local auto parts store, and
coolant is probably more like 80% antifreeze to 20% tap water. All of
resulted in coolant dissolved solids and minerals and calcium deposits
throughout the system over the years; it is no wonder that we spout off
about any kind of improvement at all.
So, adding that heavy-duty fan clutch gets just enough oomph to get
the hump and is universally agreed upon as the Holy Grail of Cooling.
Well, it is not a bad idea, my ONLY problem with this solution is
that if we
address the engineering behind the Heavy Duty Fan Clutch we find that
designed to prevent the fan from turning at the same rate of the water
shaft. Regular duty fan clutches operate at about 50-60% of shaft
heavy-duty fan clutches are in the 60-70% range. A severe duty fan
operate at 90% of its shaft speed. All will slip much more as the
of the silicon cools down a bit at high speeds.
This gives quieter operation (no howling) and perhaps better gas
Also at higher speeds, the fan is spinning more freely and thus it
horsepower and allows more air to flow through the front of the
brings up another issue, air dams can build up so as to prevent some
entering the engine compartment, due to the raised height and flow path
underneath our rigs. On some lifted vehicles, an air dam can from
the front bumper to the front engine area, thus making it harder for
from the radiator to escape, and thus affecting the bi-metallic spring
front of the fan clutch. Removing the hood and driving around a bit
this odd occurrence.
Once we put this into perspective, we realize that the fan clutch is
a boon to those systems that have been designed and are in the middle
operational parameters, so that the clutch can slip when additional
not be needed, or additional air flow may be available when required,
the clutch engage the fan and not allow it to slip as much.
Of note on fan themselves, is that AMC originally stipulated a 19.5
7-blade fan, probably around a 2-inch pitch.
I just wanted to throw some things out there to
before everyone just starts to tear into their rigs and throw parts at
potential problems, plus share some of the things that I have observed
Part Two: Individual Component
Improvements using a Copper Radiator Core
Cooling improvements to our Jeep OEM systems can be readily achieved
there are many choices in the aftermarket that cater to our needs. The
aftermarket suppliers provide various upgrades and enhancements that
utilized to achieve our cooling requirements, such as improvements in
radiator designs, aluminum radiators, electrical supplement fans and
electrical fans that eliminate the need for a mechanically driven fan,
mention improved water pump designs.
This portion of this article will concentrate on a Do-It-Yourself
project that may be accomplished over a period of time for those on a
using mostly off the shelf products that may be ordered from the
or other aftermarket dealers.
1. Hayden (P/N 2797) Severe Duty Fan Clutch.
2. Custom Industrial 5-Core Copper Radiator w/410 square inches of
3. Rigid Fixed Blade 20-inch, 7-Blade, minimum 2-inch pitch fan
4. Stant Radiator Pressure Cap (P/N 10330 or 10331-Vented)
5. Flowkooler (P/N 1781) Aluminum High Velocity water pump (Use both
6. Stewart/Robertshaw (P/N 301 180°F) or (P/N 302 190°F)
7. Filtered/Ionized drinking water with Red Line's "Water Wetter"
instead of Anti-freeze.
7. Prestone Super Radiator Cleaner each Fall and Spring.
8. Radiator (Prestone) Flush kit with T-valves and caps.
9. Fan shroud, this insures that the fan blade pulls cooling air
The above system is what I am currently running on my 1983 Cherokee
which is approaching 6,000 lbs. For you to use the components as
above, you must first insure that you will have enough room to install
particular set of components without risking fan clutch encroachment on
rear surface area of your installed radiator.
Note: The above image is for illustrative purposes; your fan will
on to the fan clutch as shown, but will instead bolt through the
pulley to the water pump.
Referring to the above picture, read the following paragraph to
you have enough room in your FSJ to use the indicated components. After
would be a shame to go out and buy all of the above components, rip
Jeep and find that as you begin to bolt the Fan Clutch to the pulley,
into the radiator, eh?
Measure from the Timing Chain cover and Water Pump mounting surface
if you have enough room You will need at least 10-inches from this
surface to the back of the radiator, if not...then the
MAY not fit.
The water pump, pulley, fan blade and fan clutch will use up about 8
3/4-inches, which gives about an inch from the front of the severe duty
clutch to the rear of the radiator fan, depending upon the depth of
This becomes important due to the fact that the thermal fan clutch
bi-metallic spring facing the rear of the radiator, and if it come
proximity to the back of the radiator, erroneous operations of the fan
will occur, not to mention the off-roading flex, where the fan blades
front of the fan clutch might come in contact with the rear radiator
Hayden (P/N 2797) severe duty fan clutch (3 5/8-inchs in height so
it won't contact the radiator cooling fins when the vehicle flexes
this fan will howl!
Typical Hayden Severe Duty Fan Clutch shown with Bi-metallic spring
housing at the center of the clutch heat sink show above.
A = 6.45-inches
B = 0.63-inches
C = 1.63-inches
D = 3.25-inches
Total Depth is about 3 5/8-inches.
This Severe Duty fan clutch engages at about 170° (F), and allows a
Silicon Fluid to flow into the two “Land & Groove” designed plates
on the right
hand side of the image below.
This increases the viscosity between the plates so that it engages
half of the clutch (Multiple Viscosity Silicone housing). The Severe
clutch turns at 80-90% of the water-pump shaft speed, and should be
deeper pitched fan blades such as 2 1/2-inch or 2 3/4-inch. Standard
clutches turn at 50-60% of water-pump shaft rotation. A 20-inch 7-blade
with a 2-inch pitch is a decent match, for the heavy duty fan clutches
the Hayden 2747.
For those of you who wish to replace your current radiator as well,
at least 1 square inch of radiator surface area per cubic inch of
motor, I have
an AMC-360 probably bored at .030 over, and my custom 5-core radiator
square inches of surface area. The custom unit is a 5-row, R-Series,
louvered 13-Fins per inch with a core that is 16-inches high, 25
and 2 7/8-inches deep. I chose to use a copper radiator for several
which closely match my driving requirements, yours may differ. The
design of my
custom radiator is similar to heavy-duty trucks and diesels over the
vehicles, where the core has stamped louvered cooling fins, and the
fully enclosed by the upper and lower tanks, in a very similar manner
I had Dnt Radiators (512) 467-0063 at 705 W. Saint Johns Ave
Austin, TX, custom design a radiator based on the Modine 581 core and
arrived very similar to the core depicted above. This is a very strong
and repairs, should damage occur, should be widely available from
Mexico. I instructed them to make a custom top tank from a copper tube
half lengthwise to which they brazed the upper radiator hose fitting
radiator fill cap to match my old radiator. Finally they brazed the
to the top (left side of picture above) of the industrial radiator
Rusty Dodd at Texas Industrial Radiators offers complete Radiator
Tank service. They are a family owned business, with the grandson
the reigns for the family. Rusty and I spent some time discussing the
ins-and-outs of radiator design and he states that he can get you a
Jeep radiator (P/N 43-6005) for $194 dollars.
I believe that this is a 4-row hi-density fin unit that will drop
our Jeeps. Rusty also indicated that he could build a more serious
the one I have, with a little more investment. You can reach Rusty at
666-5500 @ 5314 IH 10 East San Antonio, Texas 78219. These are good
they run a clean family business, with the whole family helping out to
office. Give them some business, Rusty will work with you to design
radiator design and performance levels you specify.
The upper tank of any radiator receives the hottest coolant and here
steam will be trapped if overheating occurs. My cooling fins completely
surround, and are in contact with, the 5-row core of
tubes. Each fin adheres to the entire surface area of the tubes, and
louvers stamped into each fin. There are about 13 cooling fins per
inch, which gives plenty of through flow. I have observed that my
cool as much as 40°F from the intake to the outlet, depending on
outside ambient air temperatures. I
wanted industrial strength and I got it. They used the existing bottom
from the radiator that they pulled out of the vehicle, as there is
chance of steam forming at this lower location of the cooling system
pressure side of the system.
The issue now becomes how to get enough air past that thick radiator
holding so much heat. A 20-inch 7-blade, 2 3/4 inch pitch fan from a
Dodge 400/440 Motorhome, with a Heavy Duty Fan Clutch is indeed
this particular fan seems to be fabricated out of a material we all
I pulled a 20-inch diameter fan, with 7-blades and with a 2-inch
a GMC truck in a junkyard for cooling. Shown below is a depiction of
are looking for, 20-inches in diameter and as much pitch as you can
will fit an OEM fan shroud, or at least it does on my 1983 Cherokee
since the OEM fans were 7-blade and 19.5-inches.
A custom fan shroud may just be the ticket here, with a gasket to
shroud to the back of the radiator surface. Any self respecting sheet
shop can fabricate a fan shroud out of stainless steel. The radiator
drop the temperature of the coolant by about 20°- 25° F
when the coolant flows through the radiator, at a minimum. This is the
difference between the inlet temperature and the outlet temperature of
The radiator uses a mechanical rigid blade fan with a fan clutch to
operating temperatures within operational specifications. The
Wagoneers and J-trucks with air conditioning were generally equipped
Tempatrol fan (7-blades) with fan clutches for both noise control and
control. The fan clutch utilizes a silicon fluid of specific density
upon its designation as regular duty, heavy duty or severe duty). Most
engines without air conditioning came with a 4-blade fan.
A fan shroud should be incorporated in order to insure that all of
being drawn by the fan is pulled through the radiator and not from
the vehicle. There are OEM versions available and some of the
on the message boards have been posting pictures of some fabricated
versions with electric fans.
Stant P/N 10330 16-lb Lev-R-Vent Radiator Cap
As you can see from the above and below diagrams, the radiator
a pressure relief valve used to relieve pressure and release excessive
overflows into a reservoir tank, and also to return the lost fluid from
reservoir tank back into the closed loop system, when the coolant and
lower and the pressure drops inside of the radiator.
I use a Stant P/N 10330 16-lb Lev-R-Vent Radiator Cap as shown above
further pressurize the coolant to raise the boiling temperature.
helps provide backpressure on the impeller blades, thus helping to
cavitations, a very nasty occurrence.
For every lb of pressure that you impose on the radiator tank, the
temperature that the coolant will reach before boiling will be raised
by 3° F.
So a 16 lb radiator pressure cap will raise the boiling temperature of
water by 48°F from 212° F, which is the normal sea level boiling point
of water, to 260° F.
This becomes significant due to the fact that if a vehicle looses any
due to boil over and overflow, the system cannot cool down until that
or additional coolant, is replaced back into the system, or until the
is shut down and allowed to cool.
I have a Flowkooler P/N 1781 aluminum high velocity mechanical water
mated to a modified thermostat, rated at 180° F. Opening the radiator
cap, and starting the engine and running her until the thermostat opens
reveals that there is quite a lot of water being moved by the impeller
of this pump.
Flowkooler P/N 1781
The unit is 4 13/16-inch in depth, with a 5/8-inch shaft protruding
front to center the pulley and the fan. There are (4) 5/16-inch
threaded (18 threads per inch) mounting holes as depicted in the 5A
illustration above, the fan bolt mounting holes are on a 3.25-inch
center-to-center pattern. The pilot diameter (2 above) is 0.63-inch to
the double pulley and the fan clutch.
It will require the use of BOTH gaskets that ship with the water
ask me how or why I am positive about this….trust me.
These Flowkooler aluminum water pumps are shipping with an
impeller blade, made of brass, that Flowkooler calls their MiraKool
16-blade impeller more than doubles the flow rate at idle but drops the
rate back to the idle when the engine hits 3,500 RPM's, so that
not occur in the coolant.
Flowkooler 1781 Impeller 16-Blade disk
On my FSJ, I have settled on a Stewart modified Robertshaw
a set point of 180° F. My inlet water temperature to the radiator when
at 90° F ambient temperature is
normally about 195° F, and at the outlet of the radiator, it is about
during normal engine operations. The below picture depicts a typical
modified Robertshaw thermostat. Make sure you install it with the cone
facing the sky!
One of the more interesting things about fluid dynamics is that if
double the cubic restriction areas that the coolant is allowed to flow
and maintain the pressure, you will achieve double the amount of
However, if you maintain the restriction to coolant flow and double the
pressure, you will raise the amount of coolant flow only by the square
1.414. So, a higher flowing water pump in addition to a higher flowing
thermostat, in addition to added rows on a radiator makes a lot of
The Stewart/Robertshaw thermostat has three 3/16-inch holes in the
of the thermostat, which allows some water to circulate before the
opens. This is great because it allows any trapped air to be
transported to the
upper radiator tank, rather than being trapped inside the engine
where it may form steam pockets.
Stewart modified Robertshaw Thermostat 180° F P/N 301 (195° F
A lot has been said of thermostats in posts, it is interesting to
some believe that a thermostat with a lower set point temperature, will
keep the vehicle cooler.
The OEM specifications call for a 195° F thermostat. I prefer a
180° F in the hot Texas sun. Those of you in the colder climates,
it freezes, will want to use the 195° F thermostat, so that the heater
will become available
All a thermostat can do is to start opening when their set point has
reached, and begin to close when that temperature set point is higher
coolant. In the hot Texas and Arizona summers, you want the coolant to
circulation sooner rather than later.
So a lower 180° F makes some sense. In the freezing northern
latitudes, a 195° F
thermostat set point makes more sense in the winter months, due to the
that the block and coolant in the block will reach a higher temperature
the thermostat opens, and therefore the engine will warm up faster and
will be more available heat from the heater core for the occupants.
thermostat opens, only its restriction to coolant flow will have any
Once the thermostat opens, the water flows into the radiator through
cooling fin tubes. Keep in mind that even the highest flowing water
associated high flow thermostat can only move as much coolant thru the
loop systems as the closed loop systems restrictions allow (clogged
Finally, since pure water is superior to any antifreeze on the
tend to use it to more efficiently transfer the heat from the engine to
radiator. Since pure distilled water will soon rust in the system,
anti-corrosion additives are needed, and since the water pump likes
lubrication, I use Red Lines WaterWetter® and filtered drinking water
system, during the Summer months.
Red Line WaterWetter®
The following chart is a depiction of the various materials used in
radiators and coolants; one should pay close attention to the Thermal
Conductivity of both Water (0.60) and a 50/50 Anti-freeze/water
clearly shows that water is a superior conductor of heat, and therefore
at the data one can see how water is a better thermal conductor of
heat, it can
dissipate a greater amount of heat, and can carry a higher heat load
other coolant. Therefore it is THE BEST medium to use as a coolant.
Properties of Cooling System Materials
||Heat of Vaporization
Additionally, the Red Line website (http://www.redlineoil.com/whitePaper/9.pdf)
also states "...Under moderate load conditions, each percent glycol
cylinder head temperatures by 1°F. 50/50% glycol raises head
45°F compared to water alone..."
DYNO TEST RESULTS: From the Red Line
Dynomometer tests performed by Malcolm Garrett Racing Engines showed
significant improvements in coolant temperatures using WaterWetter®.
tests were performed with a Chevrolet 350 V-8 with a cast iron block
aluminum cylinder heads. The thermostat temperature was 160°F. The
operated at 7200 rpm for three hours and the stabilized cooling system
temperature was recorded and tabulated below:
Cooling System Fluid Stabilized
50% Glycol/ 50% Water 228°F
50/50 with WaterWetter® 220°F
Water with WaterWetter® 202°F
A strong word of caution here...
if your weather conditions include freezing temperatures, then you
MUST use some anti-freeze in your
system to prevent the coolant from freezing, along with the use of
From Red Lines website "...Red Line WaterWetter® does not
increase the boiling point of water; however, increasing pressure will
the boiling point. The boiling point of water treated with Red Line
15-psi cap is 250° F compared to 265° F at 15 psi for 50% glycol.
the pressure by 50% to 23 psi will increase the boiling point of water
F. Due to the “doubling of the ability” of the coolant to transfer
over using Red Line treated water is not a problem as long as the
circulating coolant through the head and the fan is circulating air.
shutdown after very hard driving may cause boil over..."
Other things to consider are the tendencies of antifreeze additives
decompose, thus adding solvent solids to the coolant mix. Dissolved
lime in tap water are also a bother, as are the mineral contents of tap
in most locations.
Annual or semi-annual changing and flushing out all of these solids
regular basis eliminates the majority of these problems. The dissolved
seek the lowest portion of the system that they can locate and reside
many cases this leads to build ups being massed just inside the lowest
of the radiator and available to be sucked in after being jogged loose
traversing rough terrain, thereby being fed directly to the impeller
the water pump. Just go out and look at the water jacket of any ole
around to see the effects of crud and scale build up, within the water
Use Prestone Super Radiator Cleaner (the one you run for 6-hours)
back-flush kit added to the Heater Hose inlet hose (from the back of
to flush out the cleaner. Then fill with filtered drinking water
your local grocery store not distilled water), and finally use Red Line
WaterWetter instead of anti-freeze in the non-Winter months, and your
problems will be over. Rust deposits can erode cooling system
dramatically restricting coolant flow and reducing heat transfer.
These are closed loop cooling systems, and ALL components should be
addressed, along with some understanding of the systems operation
out and throwing parts at the problem.
With the above recommendations, the coolant flows through the
faster so it has less time to shed it's heat, BUT it also flows through
block faster, and therefore does not absorb AS MUCH heat...bottom line
the engine runs cooler.
The WaterWetter prevents the filtered drinking water from forming
bubbles; it increases the tension that the water clings to the internal
passages of the block, thus aiding in heat transfer. Since water has
heat transfer capabilities of a 50/50% solution of any kind of
water, you have substantially increased the efficiency of your systems
to transfer the heat of the engine to the water passing thru it.
Added turbulence from the high flow water pump and higher flowing
scrubs off vaporization areas around exhaust ports and the WaterWetter
steam bubbles from forming.
An overall system design approach.
Part Three: Aluminum radiator with
One of the great things about these Full Size Jeeps is that we have
folks with some expertise available to fall back on. One such
individual is our
own Zack Heisey (Z&M Jeeps -
http://www.zmjeeps.com) who has
with Be Cool Aluminum Radiators.
Together they have come up with an ideal turnkey solution in
radiators for your Jeep. These 100% all aluminum Be Cool cross flow
utilize 2-rows with 14 fins per inch. They have two basic models to
from, a Heavy Duty and a Super Heavy Duty model for both manual and
AMC mills. Both models reflect the features mentioned above.
The Heavy Duty models feature a core that is 22-inches Wide by
High and 2.25-inches deep, which gives it a square inch surface area of
A 3-inch tank is used. For those of you who wish to convert to an
there is available a 16-inch shrouded single electric fan that pulls
and draws 20 amps steady state. This will easily cool a 350 HP AMC-360.
The Super Heavy Duty models feature a core that is 24-inches Wide by
18.5-inches High and 2.25-inches deep, which gives it a square inch
area of 444-inches. The same 3-inch tank is used. This larger cored
radiator is also available with dual electrical 11-inch shrouded fans
of pulling 2780 cfm at 25 amps steady state.
Another “cool” feature of the Be Cool radiators is that the Radiator
positioned at the “Low Pressure Side” on the cross flow design. The
portion of any radiator is the area where the intake or inflow hose
thermostat is, on the OEM designs; you may have noticed that the
were pretty much at the hottest possible location.
Some of the readers will recognize that the above Super Heavy Duty
for a General Motors application. Not to worry, your AMC version will
correct inlets and outlets so all OEM radiator hoses will work.
You will note that the cross flow design of these radiators feature
pressure holding tank, and a low pressure holding tank that are both
vertically at the ends of the radiator, instead of the top and bottom
tanks of our OEM designs. Those OEM tanks will get very hot, trapping
that might be trapped at the highest point, thus requiring that the
caps be replaced more often.
Fluted oval tubes in these cross flow design help stimulate air
to aid in cooling, along with no epoxies, lead or solder, thank you!
radiators can even be fitted with temperature transducer bungs welded
inflow and outflow tanks per your specifications, just contact Zack @ ZMJeeps to work out the
Be Cool suggested using distilled water in their aluminum radiators,
expected, the Be Cool folks use only the finest manufacturers for their
electric fan offerings, in this case, the excellent SPAL Electrical fan
Zack has engineered a set of radiators to fit AMC, Ford, GM and they
have bungs welded into them for temperature sensors (which are
ordered with wiring kits for a total system solution. They have the
radiator design for either standard or automatic transmissions.
the GM units are available with a bung on the coolant return line
(heater) as well.
Take a close look; these units are works of art!
Check out Zack's offerings at his website: http://www.zmjeeps.com.
Zack and Be Cool have partnered together to bring our old Full Size
cooling designs into the 21st Century, to get started on
specific custom designed aluminum radiator with your specified options,
Zack directly at .
There it is in a nutshell, see if the
outlined in this article do not solve your cooling requirement. Copper
superior strength and aluminum for additional weight savings and
looks, you can have it your way!