What Are the Three Main Causes of Diesel Engines Overheating?

On Monday Truck Parts & Service published an article about the causes of diesel engines overheating. Being that we are currently experiencing one of our hotter summers on record, it seems like a good time to review causes of overheating diesels. This particular article by Bill Grabarek is addressed to heavy diesel equipment, but it applies to all hardworking diesel engines. 

An overheating engine can produce serious damage. Head gasket failure and cracked cylinder heads will give you more than a head-ache. Sometimes the damage is so severe, such as a cracked engine block, that it is irreparable.

Perhaps you have had the experience of trying to remove a metal lid that is stuck on a glass jar. One way that often works is to run it under hot water. The heat causes the metal to expand, liberating the lid from where it has adhered to the glass. 

This principle of thermal expansion is what's going on when your engine gets hot. The author points out that the normal operating temps for an engine should be between 190 and 220 degrees. Increased temperatures beyond that will put stress on the cylinder head, liners and engine block, he says. Overheating beyond these acceptable ranges "causes these parts to expand beyond the engine's tolerances." To fix the damage can run into thousands of dollars, and for larger heavy equipment the bill can amount to tens of thousands of dollars. 

All this to say that it's worth reminding ourselves of a few basic steps to avoid such a disaster. In short, a stitch in time saves nine. This is the essence of preventative maintenance.

Mr. Grabarek cites three basic causes of diesels overheating. 

Low Coolant Level or Coolant Loss
One cannot assume that they won't overheat, even if they have the correct coolant level according to the manufacturer's recommendation. Nevertheless, it is important to routinely check fluid levels because this is the first sign you'll have that there is coolant loss taking place. 

There are a variety of areas where one can have coolant leaks. Hoses, gaskets, water pump, thermostat, heater or freeze plugs are just a few places to look. Often you can smell a coolant leak. A cracked cylinder head can also be the culprit, which will sometimes produce white smoke from the tailpipe. 

Air Pockets in the Cooling System
This is a problem that can develop when replacing coolant, or when the  coolant has been drained for a repair job. Air pockets may form when refilling. These air bubbles can interfere with the flow of coolant through the hoses. If these air pockets aren't bled from the system the engine can overheat. 

Faulty Thermostat
Thermostats regulate the amount and flow of coolant by responding to temperature changes in the engine. When the engine gets too hot the thermostat opens to allow more coolant to flow through. Thermostats are a valve that can sometimes get stuck, however. In such cases they need to be replaced.

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The article ends with instructions on how to bleed the air from your cooling system. You can read the full story here.