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Ask an L&M Engineer – Clearing Up Five Common Cooling System Misconceptions

By: Tim Cass

Throughout the course of my 41-year career at L&M Radiator, I have encountered a number of myths and misconceptions about how cooling systems actually work in the field. In this article, I’d like to address some of the most common misconceptions and share my engineering expertise to provide more clarity to those who design heavy-duty equipment for applications such as mining and oil and gas, and those who are maintaining such equipment in the field.

Misconception #1: The coolant is going thru the radiator too fast to be cooled

It is not possible to put coolant thru the radiator too fast to be cooled. Higher volume flow (faster flow) always increases cooling as it increases turbulence in the tubes.  Low coolant flow results in laminar flow, in which there is no mixing of the coolant so only the outer boundary of the coolant flow is cooled.  

Misconception #2: Coolant temperature drop is an indication of performance

The coolant temperature drop across the radiator is a function of the heat load and coolant flow.  

The formula is delta T = Q (heat load) / m (coolant flow) Cp (specific heat of coolant).  

Measuring the coolant temperature drop at any point other than the design point – usually full coolant flow and full engine load – is not an indication of system performance.  If the engine is not up to full operating temperature, the thermostats will not be open, resulting in low coolant flow / increased coolant delta T.  

So how should you measure the performance of your radiator? Conduct a steady-state test at full load and either full operating temperature or blocked open thermostats. Then you can use the measured coolant temperature drop to determine if your system is performing as designed. 

Misconception #3: More radiator volume means better performance 

A larger system volume only means the coolant will take a bit longer to heat up than a system with less coolant. It does not necessarily indicate better performance.

Misconception #4: All coolants are compatible with each other

Long-life organic acid coolants should generally not be mixed with old school inorganic additive coolants.  Some long-life coolants are formulated to be compatible with the older inorganic additive coolants, but others, when mixed together, form an especially gooey gel like substance that can clog radiators internally and greatly inhibit cooling.

In general, when changing coolants, flush out the cooling systems as well as storage tanks and service truck reservoirs to avoid problems.

As always, we recommend following the engine manufacturer’s specifications for what type of coolant you should use. 

Misconception #5: SCA (Supplemental Coolant Additive) filters can be used with any coolant

When using organic acid long life coolers – do not use SCA coolant filters.  This practice can result in clogged and overheating cooling systems.

Only use SCA filters that are recommended for your coolant. 

Got a Question? Ask an L&M Engineer

If you have a question about the use of L&M Radiator heat exchangers, coolers and radiators, send them to Kerry Hecimovich at If you have a question, others may have too. Send them to us and we’ll answer them in this space.

Tim Cass is a senior engineer with L&M Radiator with more than 40-years experience in automotive and heavy-equipment design and engineering. Learn more about Tim and his 41-year career at L&M Radiator. 


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