Bulletproof cooling system

[[Image:Cooling_system.gif‎|frame|Typical cooling system.]]

An engine's cooling system transports heat from the engine, into the coolant, and out into the atmosphere. If the amount of heat that it picks up from the engine is roughly equal to the amount of heat that it dispenses to the atmosphere, the engine temperature will stay constant. "Overheating" essentially just means that the coolant is taking on more heat than it can dissipate to the atmosphere.

 

When coolant takes on too much heat, it boils. This means that the water jacket surfaces will be covered with more steam than coolant. Steam can't absorb heat like coolant can, and this exponentially exacerbates the problem: more heat results in more steam, which leads to less effective coolant, and, in turn, more boiling of coolant.

*You should use a radiator at least as large as the one that was originally used to cool the engine (not the car) from the factory, and with the same or more radiator cores. However, it's important to note that additional rows of radiators don't add a proportional amount of cooling: a 3-row radiator does not offer 50% more cooling than a 2-row. This is because subsequent rows receive warm air from the rows in front of them. However, adding radiator frontal area IS proportional, but this usually causes fitment issues, so additional rows are generally the only viable choice.

*Oftentimes, the cheapest and most bulletproof way is to use the largest radiator that will fit, along with the shroud that was designed for the radiator from the factory and the designated steel fan and viscous drive assembly for same. ''(confirm and expand)''

*Use a full shroud, with the radiator positioned so that the fan blades are half-in and half-out of the shroud hole ''(confirm and expand)'', and no more than 1" of clearance between the shroud and the fan blade tips. (Just enough to prevent intervention when the motor rocks on its rubber mounts).

*Fan recommendations: OEM 18 inch, 7-blade steel fan with 2" to 2 3/4" pitch. Pitch of a fan can be measured by laying the fan down on a flat surface and measuring from the flat surface to the edge of the fan blade. Fans that are relatively flat (such as a flex fan) won't move enough air at idle and low engine rpm's to do the job properly.  

*Thermostatically controlled fan clutch.

*Water pump and crankshaft pulleys sized according to what was on the engine from the factory. On a street motor, shoot for 1.2 to 1.3 times crank speed for pump pulley speed. This is usually true until you get to 3.55 gears and numerically higher, then 1 to 1 works better. Most all 1960's muscle cars are 1 to 1. Pump speeds over 4200 sustained cause cavitation. Nascar is a good example with roughly 3.5" crank pulleys and 8" waterpump pulleys for their 9200 rpm engines''(confirm)''

*On a carburetor-equipped engine, most of us use a 180 degree thermostat, although a little hotter thermostat (190-195) may make the motor more responsive and add a little fuel mileage. It may also help to burn off some of the by-products of operation, such as moisture and acids which form and get into the oil. Motors using EFI induction should be operated at the temperature specified by the factory for that particular motor to prevent false input to the computer and consequent problems. ''(confirm and expand)'' The sensor pill goes toward the motor.

*Ensure that there are sufficient openings in the engine compartment to allow the exit of all the air drawn into the compartment. This might require the removal or surgery of inner fender panels or using spacers to raise the hood of the car up an inch or two at the back.

*Before installing the water pump, grasp the impeller with one hand and the drive hub with the other and twist to make sure the impeller is tight on the drive shaft. Not finding this problem beforehand can make you crazy.

*Although it may not be necessary, the concept of a "water pump conversion disc" is intriguing. Flow Kooler originally marketed flat aluminum discs to rivet to the backside of the stamped steel impeller in the pump. With an iron impeller, a steel disc could be welded or brazed onto the impeller. The disc wouldn't be that difficult to fab up yourself. Space the water pump backing plate back farther with a couple of gaskets to prevent interference of the rivet heads on the backing plate if riveting a disc to a stamped steel impeller. More info: [http://www.smokstak.com/forum/showthread.php?t=11774 brazing cast iron], [http://store.summitracing.com/partdetail.asp?part=BRA%2D4375%2D07&autoview=sku Flow Kooler water pump conversion discs]. This disc should make an appreciable difference in the flow of water at engine speeds under 3,000 RPMs. On the other hand, Howard Stewart of Stewart Components (the guy with the water pump dyno), says that the disc's have little to no effect.

===Recommended donor vehicles===

 

*'76 Cadillac Fleetwood or Eldorado. For example: [http://www.radiatorexpress.com/product.asp?part=1976+CADILLAC+FLEETWOOD++%2D+8%2E2+liter+V8+RADIATOR+Name+Brand+Replacement&part_id=1357&aaia_id=1026582 1976 Cadillac Fleetwood 8.2 liter V8 radiator].

===Cadillac radiator swap===

 

The Cadillac core support will probably be longer side to side than the stock one in the recipient vehicle. Retain the outer pieces of the recipient vehicle support where it bolts into the body and cut the middle part of the recipient vehicle support out with a reciprocating saw, leaving a few inches on each side. Then, measure the opening between the two stubs that are still bolted to the recipient vehicle and cut the Cadillac support to fit into this opening. It's better to leave a little more sheet metal on the Cadillac support until you determine the correct position of the fan where it engages the shroud opening. Then, position the Cadillac support with radiator and shroud attached up to the fan, equalizing the distance between the fan blade tips and the inner circumference of the shroud all around. Move the shroud around the fan until you have the fan blades halfway in and halfway out of the shroud opening. Normally, you'll have to tilt the top of the radiator/shroud back a little at the top to match the fan angle because the motor sits in the recipient vehicle on a rearward tilt. If you need a little more front to rear clearance for mounting the support, you can position the fan blades 2/3 in and 1/3 out of the shroud opening. A little further in is OK, as long as the fan clutch is at least 1" from the radiator core material. A little further out is not OK.

With that accomplished, simply attach the middle piece of the Cadillac support to the stubs of the recipient vehicle support. Use whatever pieces of sheet metal or whatever that you have to in order to make the connection. The Cadillac support may end up sitting forward of the stubs or a little behind them or it might fall exactly into place and you'll have very little welding to do to stitch the Cad support and the stubs together. Whatever. Just use your head and figure out how to connect the sheet metal, then MIG it in place.

Now, you will have a radiator that will cool anything and you still have the stock attachment of the  stubs to the recipient vehicle so you can use simple hand tools to disassemble the whole mess later if you have to. It'll all come out as one piece  -- because it is one piece.

This swap may not be for everyone, you will have to judge that for yourself. Consideration should be given to the weight of the system when at full capacity, this could mean as much as 25 to 50 extra pounds on the front end. This swap does give you valuable information on limits of fan installation and mounting of core.

Moving the air through the radiator is one of the most important points of engine cooling and heat dispersal. In order for cooling to take place, the air MUST move through the radiator fins, and, by way of convection, the cooler air will remove the heat from the engine coolant to the outside air flow. For this to happen, the frontal area of the vehicle must be clear and the entering air must not be blocked. The radiator fins must be clean, clear and unblocked by mechanical damage, i.e. folded over fins, plugged by bugs and dirt. The air must pass THROUGH the radiator, NOT OVER OR AROUND IT. Seal up hood-to-radiator cradle air spaces with sheet metal or rubber sheeting. The fan shroud should contain at least 90% of the fan blade circumferentially and the edges should be sealed to the contours of the radiator for maximum suction by the fan.  Hot exhausted air should have an escape route out of the engine compartment. If it doesn't, make louvers or outside air scoops. Direct air to pass over the engine and exhaust manifolds or headers and out the bottom and sides away from the passenger compartment. Don't remove the rubber skirts from the inner wheel wells over the suspension, they are there for a reason. The reason is; air flow is smoothed over the A-arms and is not turbulent or 'ragged' it will flow better being more direct it will flow out of the engine compartment faster. The rubber skirt also keep road grime, stones and debris from entering the engine compartment and rad area.

If you have a external trans cooler in front of the radiator and also have a high stall torque converter, your fluid temperature in the trans cooler will pre-heat the incoming air to the radiator. If this is the case, try relocating the trans cooler to another location. Remember when doing this though, that if the car isn't moving, there is no cooling air going over the cooler to bring fluid temperatures down.

Hood removal will cause buffeting of air in the engine compartment and result in uneven pressure. Removal of side panels on three piece hoods will exhaust air better in some cases. Louvers in hoods and side panels are a godsend to ventilating hot air from the engine compartment. Fade-away fenders of the 30 's and 40's remove a lot of air from the engine compartment.

All air in front of the radiator cradle is positive flow, air after the radiator cradle is negative flow in a driving automobile. In order for that arrangement to continue, air must be evacuated from the engine compartment. When the vehicle is at a standstill, the engine fan provides flow from positive to negative and cools the engine compartment. The fan should have the ability to push/pull enough air to keep the temperature within operating range of 160 to 210 degrees.  

If you are at the drags and need to cool down between rounds, run your electric water pump and fan along with a portable squirrel cage fan to bring down the temperature.

==Water pumps: electric vs. mechanical==

Electric water pumps are constant flow pumps that push X amount of gals of water per minute, no matter what the rpm of the engine is.  

Mechanical water pumps are variable speed pumps which have decreased flow at idle and increased flow at higher speeds WITH LIMITATIONS. The limitations are that water will slip and cause air cavitation. Mechanical pumps will only operate while the engine is running, but with electric pumps, operation is user selectable.

The "usual" drive ratio of a SBC mechanical water pump is between 1:1 and 1.3:1, over driven.

In the writers opinion the LOCATION of the pump is of great importance. Some vehicles have been built with high mounted water pumps which have been a disaster.  In the case of a vehicle which has its engine mounted north-south, the water pump will often become the highest component in the cooling circuit when the vehicle is ascending a steep hill.  Engine designers ought to study Steam Trapping and Air Venting as it is a very important topic even for things that do not run on steam.

The purpose of the radiator is to get the engine up to operating temperature as quick as possible, help it maintain optimum temperature, and remove excess heat when required. "Radiator" is essentially just another name for a heat exchanger, whereby combustion temperatures up to 4500 degrees are transferred to the cooling system of the engine block and taken outside the block via flexible rad hoses to be exposed to the cooling force of air through the rad core, thus reducing the temperature of the coolant before returning it to the engine block. There are two restrictions in the system. One is the thermostat, which restricts flow and holds heat in the engine until warmed up, and the other is the rad core tubes. The rad tubes have to be of sufficient size so as to allow the coolant to flow through in an unrestricted manner, but also able to 'scrub off' BTU's or heat; which is based on the shape of the tube and the convection of heat away from the coolant to the outside air. A wide flat tube will expose more surface to the outside flow of air than a narrow tube . The reason for this is more surface area is exposed to cooling. Look at the pictures located below and see why that is.

If you are designing/redesigning a cooling system for your car, the utilization of the aluminum radiator is the best overall product on the market for the dollar. This is not to say that the radiators made from copper and brass are not good, and if you have one that works, don't go out and change for the sake of change. But, the choice of aluminum media will outperform their copper counterparts quite easily even though copper is a better conductor of heat. What is a lesser conductor of heat (aluminum) makes up with more surface area available for heat exchange. A 1.25" two-row aluminum radiator will cool just about anything up to 450hp. If designed correctly, it will outperform most 4 or 5 row copper brethren. Not only does aluminum offer a great deal more surface area for cooling, but also has a more rigid structure, making for a less likely leaky situation. Also to the credit of this technology and the fact that more modern cars are implementing aluminum, more and more vendors are competing in this product line making for very attractive pricing.  

 

When running an aluminum radiator or any aluminum parts in contact with the water jacket, make sure to run a sacrificial anode (usually zinc) to prevent the electro-displacement of the aluminum. This will save the aluminum parts, in the short run.

Sometimes the key to a bulletproof system is what you put in it and how. You can't just open the rad cap and dump anything in it. It is recognized that a 50-50 mixture of water and antifreeze is an approved OEM mixture that should be adequate for most vehicles.

Water is the basis of coolant in most systems. Can the water that you start with have a detrimental affect on your cooling system? Yes! Water is not necessarily clean and free from contaminants. Water can contain acid, alkaline, foreign matter, etc. These contaminants can combine with the metal within the cooling system and contribute to plugging or slowing down the flow within the system. Today, you will find about 10 different antifreeze products and about 30 different additives for your cooling system. WHY do you need them? Good question!

Your OEM dealer and manufacturer want you to use an approved 50-50 mix of antifreeze and water because they know and approve the source of that water and the glycol contained in that gallon jug. They know that the formula for that mix will not harm the internal metals or seals within that engine's cooling system. They also know from past experience and warranty replacement that the ditch water and pond scum that you mixed with 30 known additives that you put in your cooling system has cost them (and yourself) billions of dollars over the years. Engineers have formulated cooling system cocktails for the most elaborate machines on earth, so why not use them?

When you are refilling your cooling system, the rad cap is open, and you pour directly into the system until it is full. "Full" means a level one inch less than the cap height.  The engine should be warmed up and running at a fast idle of 1000 to 1200 rpm's. The engine is run until you can see movement in the rad and a slight steam rises from the open cap outlet. If you have a gauge, verify that the temperature is at operating temperate of 160 to 195 degrees. The cap is placed on the rad outlet and turned until tight with the arrows aligned to point at the overflow outlet. The overflow bottle should be within its limits which is usually marked on the container walls.

When you are adding to the system, do not open the rad cap, add directly to the reservoir tank.

If you have ever watched a pot of water start to boil on the stove, you will know that tiny air bubbles start to rise from the bottom of the pot as the heat is raised. Adding a water wetter to your coolant will break the surface tension and provide a greater contact area for the coolant. A wetting additive can decrease the temperature up to 20 degrees F.  

On a closed system with an overflow bottle, that the system should be filled to the top when it is at operating temperature. One of the advantages of this type of system is to reduce oxidation by eliminating all air from the system. Hence it then becomes a closed system. Why leave a head of air in the top of the radiator when you don't have to? Entrained air is sometimes difficult to get out of the system. The secret in the system lies in the overflow bottle. Coolant, due to excess heat from the engine bleeding heat through the water jackets, will expand H(ydrogen) and the O(xygen) molecules, thus increasing the total water volume's mass. This mass will bleed through the rad cap (valve) and end up in the overflow bottle which is vented to the atmosphere. When they mass is cooled due to the air flow through the radiator or turning off the engine, the rad cap will release it's thermo pressure and allow the valve to open and syphon the reserve coolant back into the water jackets, thus keeping a set amount of mass present in the cooling system.

 

 

 

 

Radiator caps are important to the proper operation of the entire cooling system. The cap is designed to hold pressure in the system. Under pressure the coolant boils at a higher temperature than when non pressurized. Check the cap gasket for cracks and other damage. If the cap pressure spring is badly rusted replace the cap, observing the pressure stamped on the old unit, acquire one with the same pressure rating. During inspection make the that the radiator fill (where the cap lives) is clean and the sealing surfaces are undamaged. A radiator with a nicked or damaged sealing surface can be repaired by employing a metal filled epoxy to fill the imperfections.

 

Recommended steps:

 

* Mix the metal filled epoxy following manufacturers directions

* apply a thin bead on the sealing surface

* using a plastic implement smooth the bead covering damage and imperfections

  make sure the epoxy is smooth and even.

== Thermostats ==

 

 

Thermostats have a “rated” temperature such as 180F or 195F. This is the temperature the thermostat will start to open, give or take 3 degrees.

As the engine's coolant warms up, the increase in heat causes the wax to melt and expand. The wax pushes against a piston inside a rubber boot. This forces the piston outward to open the thermostat. Within 3 or 4 degrees F. of the thermostat preset/rated temperature which is usually marked on the thermostat, the thermostat begins to unseat so coolant can start to circulate between the engine and radiator. It continues to open until engine cooling requirements are satisfied. It is fully open about 15-20 degrees above its rated temperature.(2.) If the temperature of the circulating coolant begins to drop, the wax element contracts, allowing spring tension to close the thermostat, thus decreasing coolant flow through the radiator.

Thermostat Failures

 

A thermostat fails “open” if the return spring breaks or debris prevents the thermostat valve from fully seating or closing. In this instance the thermostat allows continuous coolant flow to the radiator; therefore, the engine will be overcooled. The tangible effects are poor warm up and heater performance, increased engine emissions and reduced fuel economy. For these reasons, an engine should never be operated without a thermostat in place, even in extreme temperatures.

Replacement Thermostats The temperature rating of a replacement thermostat must be the correct one for the application because of the adverse affects the wrong thermostat can have on driveability, engine performance and emissions.

 

Thermostat checks One way to determine if the thermostat is doing its job is to feel the upper radiator hose after starting a cold engine. The hose should not feel hot until the engine has warmed up. If the hose starts to feel hot after only a couple of minutes, the thermostat may be stuck open or not closing completely. Once the engine is warm, the hose should feel hot as coolant circulates between the engine and radiator. If the hose does not feel hot, the thermostat may be stuck shut, blocking the flow of coolant.

Replacement tips  Don't overlook the water outlet covering the thermostat. Check for cracks, broken flanges, internal pitting and corrosion, and erosion at the hose neck (a real problem with most aluminum housings). The gasket surface must be flat and free from warping or deep scratches.  Scrape the mating surfaces on the thermostat housing and engine to remove all traces of old gasket material. Use care on aluminum because the soft metal can be easily scratched.  Temporarily stuffing a clean rag into the thermostat opening on the engine while the housing is removed helps keep debris out of the cooling system.  Install the new thermostat so the copper heat sensing element is toward the engine. If installed upside down, it won’t open.  Stant's Stat-Lok® thermostat gaskets are adhesive backed to make installation easier.  Torque the thermostat housing bolts evenly and to the manufacturer's recommendations.  To insure air has been removed from the cooling system after replacing a thermostat, be sure to run the engine a few minutes, let it cool, and refill the antifreeze as needed.

NOTE: Thermostat information; Courtesy of Chris Hoffman choffman@stantinc.com , via email. For further information contact Chris Hoffman, 1620 Columbia Avenue Connersville, Indiana 47331-169 1-800-822-3121

===400 SB Chevy engines===

400 small block chevys are a special case. The cylinder barrels are siamesed in the block so that no cooling water can pass between them. This creates hot spots or "steam pockets" in the block at lower engine rpm's which conceivably could create a spot at the top of the cylinder that is hot enough to create pre-ignition. As rpm's increase, there is enough turbulence in the cooling system to wash these steam pockets away. GM engineers cured the problem by drilling holes into the cylinder heads to relieve this pressure and allow water to flow from the block up into the heads. That's all fine and dandy if you are using a 400 head on a 400 block because the heads are drilled. But, when using any other kind of head on the 400 block, there are usually no steam holes in the heads unless you are buying new heads and specify to the manufacturer of the heads that you want steam holes drilled into them before delivery. Alternately, if you already have the heads, you can have your machine shop drill the holes or you can drill them yourself if you have proper equipment. See: http://www.gregsengine.com/350to400.htm.