Mechanics who work on heavy-duty diesel engines have many responsibilities. The customer’s livelihood, the shop’s reputation, and their own profitability weigh on the mechanic’s shoulders. Today, we’re reminding you about the importance of a relatively small but absolutely essential part of the engine: the piston cooling nozzles.
Inside the combustion chamber in a diesel engine, heat from combustion can reach over 932°F/500°C. To cool the pistons down and prevent overheating, engine oil is injected onto the pistons from below via the piston cooling nozzles. Most diesel engines have one piston cooling nozzle per cylinder. Thanks to the oil, heat dissipates, and the engine can operate safely.
Common Problems with Piston Cooling Nozzles
Mechanics most often run into nozzles that are misaligned or restricted. Nozzles can be metal or plastic, but there are risks with both. Metal nozzles can be easily bent or fractured if they come into contact with the cylinder component assemblies. Plastic cooling nozzles can be cracked or broken completely. Both of these situations can cause overheating and catastrophic failure of the engine.
How Do Faulty Piston Cooling Nozzles Cause Engine Failure?
The purpose of the piston cooling nozzle is to reduce the temperature of the piston crown. When the temperature of the piston crown gets too high, the piston skirt will expand more than the allowable tolerance. When the piston-to-line clearance is eliminated, the piston cannot move, causing piston seizure and engine failure.
A Mechanic’s Worst Nightmare
After the mechanic installs the cylinder components, the piston nozzles must be checked for proper alignment and function. Failure to ensure this small part is operational can result in catastrophic engine overheating. The customer will be unhappy, and the mechanic will be expected to complete unpaid warranty repairs on the engine. Therefore, the shop loses profits, the mechanic wastes time, and the customer experiences the costs of unscheduled downtime and will lose trust in the repair shop.
Easy Tips for Piston Cooling Nozzle Issues
The piston cooling nozzles should always be removed first before fitting or removing the pistons, connecting rods, or cylinder liners. When installing the pistons and skirts, the clearance notch must be in the correct direction to clear the piston cooling nozzle.
Also make sure that the cooling nozzles are aligned and in good working order when being installed, as gasket residue and deposits can clog the nozzle. Thoroughly clean or replace the nozzles if needed. Failing to follow the recommended oil change intervals can allow buildup to clog the nozzles.
Causes of Piston Failures
These failures can be caused by a piston cooling nozzle issue. Remember to check and clean or replace the nozzles if you run into these problems.
Piston scuffing occurs when the piston crown has rapidly exceeded the normal operating temperatures. Piston to cylinder clearance is lost due to thermal expansion. In the worst-case scenario, the piston will seize. Other than a piston cooling nozzle issue, piston scuffing can be caused by over fueling of a cylinder, lack of fresh air to that cylinder, exhaust restriction, and engine or injection timing issues.
Piston skirt scuffing happens when excessive heat builds up and spreads to the skirt area, which then expands. Similar to piston crown scuffing, clearance is lost creating scuffing. Possible causes include piston cooling nozzle failure, overheating of the coolant system, and lack of heat transfer in the cylinder.
Piston crown burning is also called piston top erosion. In this case, excessive temperatures break down the metal of the piston crown, leading to cracked or weak piston crowns. Piston burning is often caused by piston cooling nozzle failure, improper injection timing, injector contamination, lack of fresh air supply, exhaust restriction, and excessive use of ether.
Consult the OE manufacturer's service information for the correct location and area that the piston cooling nozzle or jet needs to be directed at the underside of the piston to achieve maximum piston cooling. Each engine manufacturer has specific targets for the piston cooling nozzles or jets and must be set correctly for that particular engine.
How AFA Industries Can Help
For such a small part, a lot can go wrong if the piston cooling nozzles fail. AFA Industries supplies you with the quality parts and helpful technical knowledge you need to have happy customers. By prioritizing the piston cooling nozzles, you can avoid spending time on warranty repairs, and keep your customer’s engines working smoothly.
AFA Industries has a complete offering of engine parts for a variety of Caterpillar®, Cummins®, Detroit Diesel®, and Navistar® engines to rebuild most everything on the engine. Also available are Cylinder Components, Valve Train parts, Water and Oil pumps, Cooling System Components, Fuel System Components, and other engine parts to help you repair most components for these manufacturer’s engines. Consult the OE manufacturer’s service manual for your engine’s service requirements.
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