Falling victim to radiator boil over or having your engine vapor lock while cruising through town is never a good thing. Finding yourself in the left turn lane at a red light with the engine sputtering and the temp gauge rising has certainly put some extra beads of sweat on many a brow. And while some may enjoy pushing a steaming truck through a busy intersection while Joe Public lashes obscenities, there really isn't a good reason why any of our trucks "shouldn't" be running cool to begin with. A properly set up cooling system should be able to keep even the most radical engine configurations in the most cramped engine compartments at or under a realistic operating temperature. That being said, though, it is a common problem we see day in and day out at events across the country, and even on some of our own projects. But before one can tackle a cooling system issue, we need to understand the basics of said system and what causes most vehicles to overheat in the first place.
The standard liquid cooling system is made up of passages inside the engine block and heads where coolant is circulated via a water pump and cooled by passing through a radiator, controlled by a thermostat, and pressurized by the radiator cap. The circulating coolant soaks up the heat from the engine as it travels through the water passages in the block and heads and is cooled by the airstream as it travels through the radiator. Once cooled, it travels back through the engine to absorb more heat. To ensure that the coolant stays at or above a certain temperature and that the water pump doesn't force the coolant through the radiator too quickly, a thermostat is used between the engine and the radiator. When left out, the coolant is "pushed" through the radiator and not allowed sufficient time to cool in the air stream. Conversely, the absence of the thermostat can lead to an engine that never reaches optimum operating temperature (usually between 190-195 degrees). In order to prevent the coolant from boiling, the system is pressurized, raising the boiling point considerably. Too much pressure however, can cause the hoses and other parts to burst, so a radiator cap designed to release pressure at a specified point is used. The pressure released by the cap is contained in an overflow container and plumbed on a closed system that returns the coolant back to the radiator once the pressure has subsided.
An overheating situation can occur anytime the cooling system's ability to absorb, transport, or dissipate heat is breached. This can be caused by something as simple as low coolant level or a defective radiator cap to poor airflow through the radiator. The ability of the cooling system to properly circulate coolant through the engine and radiator directly affects its ability to shed heat. When the coolant's circulation is restricted by means other than the appropriate thermostat, temperatures begin to rise and the engine starts to overheat. Additionally, if the airflow through the radiator is inefficient, such as at low speeds or due to a faulty fan, the radiator will fail to do its job.
Dirt and debris in the radiator...
Dirt and debris in the radiator core is one of the most common problems radiators fall prey to and can greatly reduce its ability to dissipate heat. Here, Don Armstrong, from U.S. Radiator, uses an oscilloscope to check on the condition of a radiator core.
Having a vehicle that has a tendency to overheat can be a frustrating predicament to say the least. Stuck in traffic with a climbing temp gauge can make for an extremely stressful afternoon. And when this becomes your experience every time you take out your ride, those trips are going to become less and less frequent. Armed with a bit of knowledge on how a cooling system functions, however, can be the difference between a truck that overheats and a truck that's used to overheat.
Hot Tips For Your Cooling System
* Ensure that the timing and carburetor are adjusted correctly
* Use the proper pressure radiator cap with a sacrificial anode for your radiator.
* Choose a radiator that is equal to or larger than the original radiator for the engine application, not the vehicle. This is a case where bigger is almost always better.
* Ensure that the lower radiator hose is equipped with a spiral-wound spring inside to prevent collapse.
* Use the proper ratio pulleys in the correct pairing to ensure that the water pump is driven at the applicable speed in relation to the crank.
* Whether it's electric or mechanical, the cooling fan needs to be properly shrouded in the radiator. No more than 1-inch clearance between the shroud and the fan blade tips with the fan mounted midway in the shroud is ideal.
A high-flow Superstat thermostat...
A high-flow Superstat thermostat can flow around 22-28 gallons per minute (GPM), which is a huge increase over a standard thermostat and can oftentimes make or break the cooling system.
* Use a 50-50 mix of water and ethylene glycol (coolant).
* Back-flush the cooling system whenever possible to eliminate any foreign objects/debris that may gather in the cooling passages.
* Use a 185- to 195-degree Superstat or equivalent high-flow thermostat (with appropriate cap pressure).
* Ensure that the overflow tank on your cooling system is adequate to collect the coolant that is purged from the system. A tank with a quart to a quart and a half is typical for a V-8 system.
* Ensure that there are sufficient openings in the engine compartment to allow the exit of all air drawn from the front of the vehicle.
 If your radiator looks like...  If your radiator looks like this, chances are, it's shot as a whole. Furthermore, the old "honeycomb" style construction core radiators aren't meant to withstand today's cooling system pressures, so that alone is reason enough to step up to a good modern unit. |  Here's a radiator core that...  Here's a radiator core that came into the shop whose owner complained of an overheating condition. The blocked tubes are easily visible on the right side of the core. Further inspection revealed a total blockage of approximately one-third of the radiator core due to foreign object debris. This particular core is a four row with 3/8-inch fins on 1/2-inch centers. |  US Radiator's Tripleflow Desert...  US Radiator's Tripleflow Desert Cooler monsters feature everything you'd ever want in an aluminum radiator-and then some. Between its die-stamped and TIG-welded tanks is one of the toughest cores built, hence its name. |
 Sufficient airflow through...  Sufficient airflow through the radiator at all engine speeds is essential. |  Whether provided by a mechanical...  Whether provided by a mechanical fan driven off the engine pulleys or an electric fan, both need to be complemented by a well-built shroud that directs all the oncoming air through the radiator. If it's a mechanical unit, an 18-inch, seven-blade steel fan with a 2- to 2 3/4-inch pitch is ideal. |  To measure the airflow at...  To measure the airflow at idle, Don uses an anemometer placed in front of the radiator. This device tells Don if there are any dead spots in front of the radiator where the fan is not pulling air through and also gives him a baseline to compare other fans to if he decides to swap out the current one. |