Low-Flow Radiator Story
If you ever wondered about how low-flow radiator systems work, or how they are constructed, I invite you to read this story of the radiator in my truck.
Last year my 400 hp. Big Cam IV Cummins engine began over heating whenever the outside air temperature topped 100 F. After doing my best to blow out and pressure wash the radiator core, the overheating continued. Not knowing how a low-flow system works, I gave Cummins Tech Support a call to get an explanation.
Cummins Tech support explained the low-flow system was developed to lower nitrous oxide emissions by lowering the coolant temperature flowing through the turbo aftercooler. The low-flow system is the predecessor to the air-to-air aftercooler that is used on today’s turbocharged engines. High-flow cooling systems typically have about a 7 degree F. temperature drop from inlet to outlet. The low-flow system has about a 20 degree drop. The larger drop occurs because the low-flow radiator is divided into multiple section sections with the use of baffles in the top and bottom tanks. My radiator is divided into three vertical sections. The hot coolant from the engine flows through the inlet of the top tank. This tank has a partition baffle that confines the coolant to pass down the left one third of the core. At the bottom the coolant passes to the center one third of the core and is blocked by a baffle in the bottom tank from getting to the right one third of the core. The coolant must now rise up the center of the core back to the top tank and then back down the right one third of the core. This looping through the core results in a greater drop in temperature compared to a straight through style radiator. This cooler coolant is then pumped directly to the aftercooler and then on to the engine. The total heat dissipation is about the same in either system of the same core size. It’s just that the flow and outlet temperatures are different. One third the flow, at three times the temperature drop, is about the same BTU of dissipation as three times the flow and one third of the temperature drop.
Once I got the basic understanding of the theory of operation of the low-flow system, I decided to pull the radiator out and have a closer look. Once the AC condenser was removed from the front of the radiator, I could see debris that the pressure washer missed. No doubt this was a major contributor to the overheating. Since I had already begun the removal process, I decided to take the radiator in and have the tanks pulled for a closer look to be sure the baffles were still in place. The core tubes were clean but six of them, in the inlet one third, had black silicon blocking the openings. This silicon most likely came from an over application to some other component of the engine. The clear silicon around the baffles may have leaked a bit so as to bypass the full loop through the core.
Because of the in field and off road use of this truck, it was decided to build a new core with a wider fin spacing. This would allow for easier cleaning. To make up for the wider fin spacing, two more rows of tubes were added to bring the BTU rating of the new core closer to that of the original. Fuzzy's Radiator Manufacturing, in Borger, Texas, designed and built the new core for me. They allowed me to watch and photograph the process. At 8:00 am they began tearing down and measuring the original core. A new pattern was chosen and the manufacturing process began.
Take the following photo tour and see for yourself how a radiator core is made.
8:30 a.m. brass top and bottom tank plates are sheared
8:35 a.m. The program is entered and sent to the CNC punch presses
8:45 a.m., after brass end plates are dipped in solder, the punching begins
8:50 a.m., on another press, a brass coil enters the fin punch
Punched fins start coming out of the press
Fins from press are stacked.
9:45 a.m. fins are slid into the stacking table
Solder coated core tubes are cut to length
10 a.m. stacking is complete
Core tubes are now inserted through the fins
10:20 a.m. tube insertion is nearly completed
10:30 a.m. last tube is inserted
All tubes are in place
Punched header plates are bent slightly in brake to stiffen
Core is now squared up
Flux is sprayed on core before entering oven
Each core tube was coated with solder prior to insertion into core. Core is now slid into oven and heated to 560 deg. F. This will melt the solder and bond the fins to core tubes
11:30 am core is removed from oven and air cooled. Notice the brass core has taken on a copper color appearance.
Stiffener plates are installed on all four corners of core for additional support. The outside tubes on each side of radiator are clipped and not used. This provides a buffer zone to guard in case someone uses too long of mounting bolts on radiator frame.
Low-flow baffle locations are marked
Tubes are clipped off where low-flow tank partitions are located
Clipped tubes
Header plate is placed on core top and bottom ends
11:25 a.m. plate fitting is completed
12:00 noon header plate soldering is completed
Holders are installed for silicon sealer bead to mate with tank baffle
Notice the baffle in on the inlet one third of portion of tank
1:30 p.m. final assembly of tanks and frames
2:00 p.m. radiator is pressure tested and ready for painting
Thanks to Fuzzy's Radiator and crew for a fine job!
Fuzzy's phone number is 1- 806-273-5911
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since 20 May 1999