Keep Your Cool


Cooling has been an ongoing issue for our classic and custom automobiles ever since weíve been playing in that arena.  The issues can be resolved with high dollar radiators, super pumps, shrouds, and any number of snake oil deals.


Now the facts:


There are several things that need to be done to insure proper cooling of your automobile.  


But first..............




1.     You need coolant in it.  Yep.  Plain water cools better than a 50/50 mix of antifreeze and water.  Debug your cooling system on plain water (fixing leaks, trying different thermostats, etc.) and then, when itís all working properly, switch to half water and half coolant for protection from freezing OR to 25% antifreeze if you want your engine to run cooler and still maintain some anti corrosion properties in the system.  Remember though that 25% antifreeze protects down to 10 degrees above freezing. 33% antifreeze protects down to 0 degrees.  Some drain the coolant from their cars in the fall before storage. If you live in an area where it's not that cold in the winter then you'll be fine.  Use your head.

2.     FLUSH THE COOLING SYSTEM.  All of it!  The whole deal!  Get a cooling system flush product and follow the directions on the bottle.  A dirty cooling system, and that includes the block, wonít cool as well as a clean one.  Thatís a fact.

3.     We need to DETERMINE if the water pump is WORKING!  Donít assume anything.  Water pumps have a problem with their impellers deteriorating.   You wonít know youíre missing an impeller or have a problem until itís too late.  Hereís a simple test.  Remove the thermostat.  Bolt everything back together.  Start the car with the radiator cap off.  You should SEE water rushing past the radiator cap opening.  If you donít then something is going on that needs correcting.

4.     Remember that most cars really like a shroud of some sort that directs the flow of air OUT of the radiator.  That is, since the fan PULLS air through the radiator youíll be MUCH better off using a shroud.  Youíll want the fan about 2/3 of the way BACK into the shroud from the backside of the radiator.  This isnít always possible but itís good to get it as close as you can to the 2/3 distance.  Sealing the area AROUND the radiator helps a GREAT deal. This forces the air to flow through the radiator.  If air is going around the radiator then it's not extracting  heat from the radiator.

5.     Radiator caps are important.  Yep, they are!  Coolant at 16 pounds of pressure has a higher boiling point than coolant at 2 pounds of pressure.  Laws of physics apply here.  Itís not just a good idea, itís the LAW.  Youíll run cooler at pressure than you will with no pressure.  Remember to get the correct cap for your application.  Youíll not want to run a 16 pound cap on a system designed to run at 8 pounds. 

6.     Running your engine without a thermostat (with the exception of our test in #2) is fallacy. An engine will run cooler initially without a thermostat.  After that IT WILL NOT!  Why you ask?  Again,  physics.  An engine running without the restriction of the thermostat in the system (remember, even when itís wide open thereís still some restriction in the system caused by the thermostatís small opening) will not keep the coolant in the radiator long enough for the radiator to Ďradiateí the heat.  That is,  the coolant must stay in the radiator for a certain amount of time to dissipate some of the heat it has absorbed from being in the engine block.  The coolant is in the block.  Itís hot.  It moves to the radiator and gets rid of some of the heat.  If it moves through the radiator too FAST, without the restriction of the thermostat body,  it wonít get rid of as much heat.  Thermodynamics R Us.

7.     The lower the temperature Ďsettingí or rating of the thermostat the better?  Perhaps.  Itís easier to keep an engine cool than it is to cool it after itís hot.  If we can get our engine to run along at 180 degrees (82 degrees C)  then weíre happy as clams.  The reality is that we will want the engine to run there as an average.  Itís going to run warmer in traffic, stop and go, than on the highway.  Seeing 190 in traffic is fine.  Seeing 180 on the road is peachy.  Running at 150 is too cool.  Generally, engines prefer 180 or so.  Arguably 180 is about nominal.  Newer engines run around 200 to 220 or so but thatís not where we want our street rod (unless itís an L1 crate engine or the like) to run.  Our TR6 is very happy at 170-180.  The Spitfire will like running around the same temperature.  Your small block Chebby or RB 440 Mopar will be joyus if you set it up to run around 180 degrees.

8.     A 160 degree thermostat is probably a good place to begin.  That is, the thermostat will open when the coolant temperature reaches 160 degrees (71 degrees C).  This allows the coolant that is ďtrappedĒ in the engine block to start to FLOW through the radiator and have itís heat removed.  If you watch your temp gauge carefully youíll see, just as you reach 160 degrees, the temp will DROP 5-10 degrees or so.  That sudden rush of cooler liquid thatís been sitting in the radiator will drop the temp a bit.  Of course it will go back up as things run along but thatís normal.  If you wish, you can test your new (NEW) thermostat by putting it in water on the stove.  Use the candy thermometer to see at which point the thermostat actually opens.  A new, 160 degree thermostat will open within 5 degrees of itís rated temperature (usually right on the number).

9.     Snake Oil, or making water more wetter than it comes from the factory. Does this stuff work?  Depends on who you talk to.  Some people claim thereís nothing to it.  Some people claim itís the beeís knees.  Iíve never used the stuff and, therefore, have no basis for comparison.  Try it if you like,  donít if you donít.  A properly functioning cooling system wonít need miracle chemicals to make it work.  If itís broke youíre not going to fix it with different chemicals.  The key to water's ability to extract heat is it's 'surface tension'.  The better it adheres to the walls of the cooling passages the better it will pull that heat out and carry it to the radiator.