Bulletproof cooling system

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

;Note- All temperatures are in degrees Fahrenheit.  

*A rough guide is to use a radiator at least as large as the one that was originally used to cool the engine, with the same or more radiator cores. However, it's important to note that additional rows don't add a proportional amount of cooling, i.e. a 3-row radiator does not necessarily offer 50% more cooling than a 2-row radiator. 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. Also the radiator design and materials can have an affect on the radiator efficiency; a larger radiator is not necessarily a better radiator.  

*Thermostatically controlled fan clutch.

*On a carburetor-equipped engine, most of us use a 180º thermostat, although a little hotter thermostat (190º-195º) 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 combustion, such as moisture and acids which form and get into the oil. Motors using EFI induction should use the thermostat temperature specified by the factory for that particular motor to prevent false input to the computer and consequent problems. The sensor pill goes toward the motor.

*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 cause damage.

 

'''NOTE:''' While a thermostatically modulated fan clutch is an effective means of operating the cooling system's fan, a worn or defective fan clutch can cause overheating if left undiagnosed. Sometimes they may appear to be OK when cold but they will free-wheel when hot.

===Recommended donor vehicles===

====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 half in and half 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.

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.

With a transverse engine vehicle it is possible to have the water pump behind the engine block.  With this arrangement steep hills will not starve the pump of water. AVOID any car that relies on venting screws in its cooling system.

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

 

Radiator shrouds are devices that control the exiting air from the radiator and direct it to a rearward sucking electric or mechanical fan. Shrouds can be made from plastic, fiberglass, and metal (aluminum or steel). They cover the rear portion of the radiator. Allow air passing through the radiator to be ducted to the fan which directs air flow over the engine and out of the engine bay. In most cases, the mechanical fan will be inserted approximately 1/3 of the depth of the fan blades into the shroud, this is usually sufficient to draw a full charge of air and disburse it adequately without disrupting air flow.

 

A radiator cap is 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;  approximately 3º per 1 psi so a 10 psi cap will add 30º to the boiling point of the coolant. 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 sure that the radiator filler neck (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:

 

== Thermostat ==

 

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

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 3º or 4º 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 15º-20º above its rated temperature. 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'''

 

'''Thermostat checks'''

 

'''Replacement tips'''

 

==Miscellaneous==

The 400 SBC is 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.

'''OIL COOLERS:'''

 

Some cars will have the oil cooler installed in the radiator. In the writers opinion this is an extremely bad idea as (1) Regarding cooling, one has all ones eggs in one basket. (2) There is the risk of oil getting into the water or vice-versa.  Note that an oil-to-air heat exchanger is extremely difficult to boil and it is a reliable method of getting rid of waste heat.

 

Regarding combined coolers, allegedly a £57,000 German car uses a transmission cooler in the radiator for its fancy six speed gearbox.  For some reason (allegedly the transmission fluid attacking the pipe) leaks occur.  When this happens, the pressurized engine coolant fills the gearbox which then explodes!  The owner of the car has had this happen twice in two years and he describes the car as "Fifty seven thousand pounds-worth of c#@p" (however he needs it for his business). My own British made car has six heat exchangers and NONE of them are combined.  This gives better reliability even though it is old and only cost about one percent of the price of the German limo.