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Sleuthing Out Radiator Fouling

Engine-cooling issues fall into one of two categories: obvious or elusive. One issue many farmers and mechanics are not familiar with is radiator fouling. It can happen to any heat exchanger. 

There are different types of heat exchangers. Some are liquid-to-air styles such as a radiator or a hydraulic oil cooler. These cool the liquid by transferring heat to the atmosphere. The liquid is sent through tubes that have exterior attached fins. Heat is transferred to the fins and then to the atmosphere. It is imperative for the fins to touch the tubes so thermal transfer can occur.

The design of the fin increases the surface area exposed to atmosphere. If the fins are damaged, dented, or closed, the level of heat transfer drops substantially. As the radiator ages, the fins can move slightly from the tubes, or they may deteriorate, limiting efficiency.

There are also liquid-to-liquid exchangers normally found in some irrigation engines. This heat exchanger is identified as a tube bundle. The hot coolant goes through a tube as it would in a normal radiator, but the entire unit is immersed in water. Since well water is normally around 54°F., it is an excellent medium to cool the engine while still using antifreeze in the engine block. 

Another heat exchanger is the air-to-air intercooler found in a diesel engine. The compression of the turbocharger along with thermal transfer from the turbine side of the turbo elevates the temperature. The air courses through the tubes of the intercooler and heat is rejected to the atmosphere. There are air-to-liquid intercoolers, but they are normally found in automotive applications.

inspecting for fouling 

When inspecting a radiator, most look inside to check for corrosion on the tubes. This is a very valid test since any accumulation will limit liquid flow of the coolant. If nothing is seen, then the radiator is often given a clean bill of health. However, the unit may be fouled.

Radiator fouling is the accumulation of foreign material in the lower part of the tube that cannot be seen from the fill point. This accumulation blocks flow and, over time, may diminish the effective size of the radiator.

In a down-flow radiator, the fouling occurs in the bottom tank and it eventually will block all the tubes. With a cross-flow style, it begins in the bottom row of tubes and works upward. The foreign material can be composed of deteriorated internal cooling system parts, rubber from hose degradation, or the introduction of dirt into the cooling system. A fouled radiator can look perfectly clean at the top of the tubes, so this needs to be kept in mind.

If you suspect fouling, the best method is to have a radiator shop remove the tanks. Then it will be obvious. Once the tanks are off, the core can be washed and put back into service. At the farm, the first step would be to employ an infrared temperature gun and track the coolant path in the radiator. If the temperature is dramatically lower at the bottom of the tubes, that is a good reason to suspect fouling. Pull the unit and have the tanks removed. 

An intercooler can become fouled by a bad seal on the turbocharger shaft or from a nonfunctioning crankcase ventilation system. The unit will then become oil fouled and limit thermal transfer.

Oil fouling usually impacts all of the tubes, but the accumulation will be in the lowest part of the intercooler. Once the source of the oil is repaired, the intercooler can be washed out with mineral spirits and then blown dry with shop air. Thus, there is no need to remove the tanks.  

When chasing a heat exchanger issue, do not allow your diagnostics to get all fouled up! 

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