The automotive engine cooling system has a long history that dates to the early days of the internal combustion engine. The radiator is a crucial and most visible component of a vehicle’s cooling system. It is responsible for dissipating heat from the engine to prevent overheating. The radiator transfers heat from the engine coolant to the air, maintaining optimal engine temperature for efficiency and longevity.
Above: Chrysler designed a quality water-cooled system that was refined over the years. By the time of the muscle car, the cooling systems and radiators were superior to those developed decades earlier. In the last five decades, cooling systems and radiator technology have advanced to near perfection. Glen-ray provides some of the best radiators for the muscle car era Mopars.
Early cooling systems (late 1800s) were highly primitive. Often, the engine was cooled by air or water jackets surrounding portions of it. Karl Benz’s 1885 Patent-Motorwagen featured a water-cooled single-cylinder engine with a rudimentary evaporative cooling system, where water would boil off and require frequent refilling.
Above: The Benz Patent-Motorwagen, constructed in 1885, was powered by a single-cylinder four-stroke engine with a primitive cooling system. It is considered the first actual automobile due to its use of gasoline as fuel and its design intended for optimal practical use. (Photo – garagedreams.net)
Wilhelm Maybach, working with Gottlieb Daimler, is credited with developing the honeycomb radiator in 1901 for the Mercedes 35 HP. The design increased the surface area and cooling proficiency. These early radiators worked on a thermosyphon principle (water pumpless system). Hot coolant rose naturally through the system and was cooled in the radiator by air before returning to the engine block.
Above: The honeycomb radiator found its first practical application in the Mercedes 35 HP. It is characterized by its unique design of closely spaced, hexagonal cells, which significantly enhance the surface area available for heat exchange. (Photo – Motor.com)
When Walter P. Chrysler reorganized the Maxwell Motor Company into the Chrysler Corporation on June 6, 1925, air-cooled engines were primarily restricted to low-horsepower, RPM-limited, or constant RPM engines. Over the years, Chrysler (and its subsidiaries) limited the usage of air-cooled engines almost exclusively for prototypes as water cooling proved to be the most efficient and practical for production vehicles.
In 1904, when Maxwell introduced its first car, the Model L, it featured a two-cylinder, water-cooled engine. The engine was mounted transversely (sideways) under the seat, like early Curved Dash Oldsmobiles. The engine design relied on natural coolant flow (thermosyphon), airflow and cooling fins to dissipate heat. However, overheating concerns and inefficiency led Maxwell to switch to water-cooled engines with water pumps in later models.
Above Left: Many early vehicles’ cooling systems were developed without a water pump. It operated via a thermosyphon design, which relied on water movement based on heat exchange. (Photographer – unknown) Above Center: The Maxwell (predecessor to Chrysler) Model L operated with a thermosyphon cooling system. Air-cooled and thermosyphon systems proved less efficient than water pump systems. (Photographer – Corey Escobar) Above Right: The Dodge Brothers had an indirect tie to Franklin Automobile Company. The engines were air-cooled. Franklin moved its focus to aircraft engines and eventually became part of Tucker. (Photographer – Greg Goebel)
Dodge never mass-produced an air-cooled automotive engine, but its connection with the Franklin Automobile Company had an indirect association with air-cooled engines. Franklin was known for its air-cooled aircraft engine designs, but after prototype development, Chrysler ultimately focused on water-cooled designs. Franklin eventually became a subsidiary of the Tucker Corporation from 1948 through 1961 and eventually went out of business in 1975.
During the development of the Chrysler Airflow (1934-1937), engineers briefly considered an air-cooled flat-six engine. However, due to problems with cooling efficiency and durability, the project was scrapped in favor of water-cooled inline-six and inline-eight engines.
Above: During World War II, Chrysler developed engines for the Sherman tanks. The engine was five cast iron six-cylinder engines wrapped around a single crankshaft in a radial design. The construction appeared complex, but its simplicity and ease of repair made it a favorite with the military. The engine weighed in at over 5,200 lbs., but it was robust. The tank could still move as long as twelve cylinders operated (after damage had transpired). (Photos – Oldmachinepress.com)
Throughout World War II, Chrysler developed water-cooled radial engines (A57) for military use, mainly in tanks. Dodge participated in producing components for these 30-cylinder engines but did not use them in Dodge-branded civilian vehicles.
It is rumored that in the early 1950s, Chrysler developed an experimental air-cooled V4 engine to compete against compact and fuel-efficient vehicles like Volkswagen’s Beetle. Despite successful testing, Chrysler ultimately did not mass-produce the engine, instead continuing with traditional water-cooled V8s and six-cylinders.
Above Left: Ethylene glycol began being used in the late-1930s. It was a much better fluid medium to remove heat than the alcohol-based liquids used up to that date. Above Right: When at war, innovations often occur. Chrysler helped in the war effort, and its work helped the country win, but it also assisted the automotive industry to move forward at a staggering rate. (Photos – Newspaper advertisements)
As engines increased power, liquid cooling systems became more popular and efficient, incorporating water pumps to circulate liquid more effectively. By the time of Chrysler’s incorporation, all vehicles used brass and copper radiators, which had excellent heat dissipation properties.
Known and experimented with since the 1920s, Ethylene glycol’s widespread use in 1937 as a commercial antifreeze moved automakers and coolant manufacturers away from less efficient alcohol-based coolants to a more stable liquid for cold weather usage. It was the first revolutionary coolant that led to today’s array of coolant options.
Above: By the late 1940s, the cooling system was becoming more advanced and took on the appearance of a modern vehicle. Chrysler still had a pressure-less system as late as 1948 (as depicted in the photo of a DeSoto), but it soon moved to a pressurized system to increase the boiling point of the coolant. (Photo – P15-d24.com)
The pressurized radiator cap was a pre-war innovation that permitted the cooling system to function at higher pressures, raising the coolant’s boiling point and improving efficiency. It took Chrysler until after the war to move to pressurized systems for civilian vehicles. As in nearly every war, significant advances occurred during World War II. Military vehicles required robust cooling systems, leading to improvements in radiator assemblies.
After World War II, radiator core designs slowly moved from honeycomb styles to tube and fin designs. The downflow radiator was the construction of choice from the beginning of the water-cooled engine until the 1970s (with a few exceptions).
Above Left: Low-pressure radiator caps (4- and 7-lbs. caps) appeared in the early 1950s. Cooling system efficiency increased during this period due to the pressurized systems. Above Right: However, honeycomb radiators were still used, but within a decade, they would become a thing of the past. (Photo – P15-d24.com)
Downflow radiators have heated coolant that enters the top tank and moves downward through the core, giving off heat to the oncoming air before entering the bottom tank. Because of its simplicity, Chrysler employed the design from its inception through the muscle car era and into the 1980s in rear-wheel drive cars and trucks. The upper tank of a downflow radiator design controlled the coolant expansion until closed systems with a reservoir were developed.
When Chrysler lowered the hood lines to increase fuel mileage in the 1970s, the crossflow radiator design became more popular. In this design, coolant flows horizontally from one tank to the other. The crossflow construction was more efficient but required an overflow reservoir to contain expelled (expansion) coolant during engine operation.
Above Left: The downflow radiator design was the construction used from the beginning of cooling systems until the 1970s. Above Right: The crossflow radiator design increased in earnest in the 1970s when greater efficiency and lower hood lines became required. (Photos – Summit Racing)
The core types include a single core with a limited number of tubes, efficient for stock or mild-performance applications; a double core (two-row) used to increase capacity, common in performance and towing applications; and triple or quad core construction, which is used for high-performance applications but can sometimes reduce airflow efficiency.
Above Left: Double pass radiators have become more common in late-model Mopars. They are common for performance and towing applications. Above Right: Triple pass radiators are for extreme cooling and are rarely needed in street-driven Mopars. (Photos – Summit Racing)
Radiator core construction is usually one of two types: louvered fin or straight fin design. The louvered fins allow for increased airflow and cooling but can clog more quickly, while the straight fins have a more straightforward design and are used in heavy-duty applications. In the 1970s, aluminum radiators with louvered fins became widespread among manufacturers. Aluminum radiators were lighter and equally as efficient in heat removal as copper-brass radiators.
Belt-driven mechanical fans were common on older vehicles to aid airflow at low speeds but consumed engine power. Fan clutches were used to reduce horsepower losses. Additionally, shrouds attached to the radiator housing helped direct the airflow more usefully across the radiator’s core.
Above: Yearone.com has plenty of radiators for many applications. U.S. Radiator and Champion Cooling Systems make quality copper-brass and aluminum radiators.
Electric fans became more prominent when Chrysler moved to transversely mounted, front-wheel drive vehicles in the late ‘70s. Electric fans are more proficient and are automatically controlled by temperature sensors to operate when needed and remain off when not required.
Today’s radiators use plastic and aluminum construction for weight savings and cost efficiency. Advanced computer-controlled cooling systems with electric fans and thermostatic controls help improve fuel mileage. High-performance and race cars utilize high-flow, multi-core radiators, sometimes with active cooling elements like misting systems.
Above Left: Late-model radiators use plastic tanks on an aluminum core. Many manufacturers use plastic because it is a much cheaper material to use than metal. Above Right: An aluminum and plastic radiator’s weight savings make it very attractive for manufacturers. The radiators tend to be narrower than the older style radiators and can be part of a cooling module, which includes the air conditioning condenser, oil cooler, intercooler, power steering cooler, and transmission oil cooler.
Active grille shutters and heat exchangers improve aerodynamics. Hybrid and electric vehicles (EVs) still use radiators to cool the batteries and electronics, leading to new designs for thermal management.
Modern aluminum radiators are more efficient in real-world applications because they use larger, more optimized tube designs that compensate for aluminum’s lower thermal conductivity. However, copper-brass radiators remain more durable and repairable, making them ideal for classic restorations and heavy-duty applications.
Above: To reduce aerodynamic drag, manufacturers have designed active shutter grills that open when more cooling is needed and close (to a point) when less cooling and more fuel efficiency are required. (Photo – Standardbrand.com)
The radiator has advanced dramatically from simple evaporative cooling to being part of today’s high-tech, lightweight, and efficient systems. Next month, we will delve deeper into fans, radiator caps, transmission coolers, and overflow reservoirs.
