1) Inspect the Coolant Level:
The most obvious system to inspect upon discovering overheating issue is the coolant level. If the coolant is too low this can allow pockets of air into cooling system. When air gets into the cooling system it will cause a reduction of coolant flow due to the presence of air bubbles. Air flow alone isn’t going to get the job done to keep engine temperatures constant. If you find coolant levels to be too low simply add more coolant to the engine.
Other causes of air bubbles is the deterioration of the cylinder liner. When the combustion cycle occurs it causes tremendous pressures up to 65,000 psi with in the cylinder liner. Over thousands of hours of operation, upon combustion, the liner beings to vibrate violently within the engine block injecting air back into the cooling system. These tiny bubbles can then do damage to the liner in the form of pitting (cavitation) and eventually eat away the liner all the way to the cylinder bore. These holes will allow coolant to leak into the bore and reduce coolant pressure. The addition of a supplemental coolant additive is recommended to provide a protective layer of chemical nitrates to prevent liner damage.
2) Check the Coolant Quality:
Diesel Antifreeze and Coolant Matching the quality of the coolant to what is already in the engine is important. The consistency of the coolant should have the following properties:
• Color that is similar to the old coolant used
• Odor that is similar to the old coolant used
• Coolant that was manufactured recently
• Coolant that is free of dirt or particulate matter
If the new coolant does not roughly match the coolant in the engine do not add the new coolant and “wing it”. It is advised to drain the current cooling system and then flush out any leftover coolant. One the system is clean refill the cooling system with the correct amount of coolant, anti-freeze and water. Overheating can occur when two different coolant mixtures reach different boiling points. Follow the engine operations manual to the letter. For example a CAT 3306 will require more coolant than say a Cummins 4BT.
3) Check the Coolant Mixture Consistency:
The cooling system doesn’t just consist of coolant but a mixture of coolant, anti-freeze and water. The ratio is very important to each engine. The mixture should approximately be 50% water and 44% antifreeze and 6% coolant conditioner. Minimum antifreeze levels for Caterpillar engines must consist of at least 30% ethylene glycol based antifreeze. Coolant is very alkaline and coolant conditioner helps neutralizes the coolant from deteriorating the engine. It protects the stems, bearings, etc… The coolant conditioner stabilizes the cooling system and is very important. Make sure to flush the engine before adding any new coolant product or conditioner to the engine.
Diesel Engine Coolant4) Check for Air in the Cooling System:
Air can enter the cooling system in many different ways. Abrupt inflow of air in the cooling system is a different diagnostic issue than air bubbles from caused by combustion pressure as mentioned in point #1. The following are the most common ways air ends up in the cooling system:
• Incorrect filling of the cooling system
• Large combustion gas leakage into the cooling system
• Loose Hose Clamp
Combustion exhaust can make it way into the cooling system in a number of ways including a damaged cylinder head, cracked cylinder head gasket, liner cracks or through a dropped valve. Exhaust gas is naturally much hotter and will cause engine overheating. The loose hose clamp is something a lot of mechanics often overlook but this simple issue can allow air into the cooling system which causes a reduction in the cooling capacity of the coolant/anti-freeze mixture.
5) Inspect Temperature Gauge:
Sometimes there is absolutely nothing wrong with the internal cooling system but rather a faulty temperature gauge, sensor or thermostat. If a gauge isn’t working properly don’t immediately replace it. Temperature diagnostic systems might simply need to be re-calibrated.
Troubleshoot Radiator Core For Overheating
6) Malfunctioning Sending Unit:
In some diesel engines the temperature sensor works in conjunction with an electronic sending unit. The sending unit converts temperature readouts to electrical impulses which are then converted to the mounted temperature gauge. If the sending unit is malfunctioning it can give incorrect or missing data to the temperature gauge. Consequently if the wire from the sending unit to the gauge frays or shorts out it can cause the temperature gauge to not work correctly.
7) Inspect the Fan Drive System and Adjacent Components:
The fan drive that is malfunctioning can cause lack of air flow over the radiator core. For example, the timing of the fan drive system in a Cummins 4BT diesel engine dictates the air speed over the radiator; too slow a speed can cause engine overheating. Lack of the proper air flow can cause the coolant not to cool to the proper temperature differential.
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