Causes of Melted Piston Top and Ring Land on Diesel Engines - Engine Builder Magazine

Causes of Melted Piston Top and Ring Land on Diesel Engines

Signs of melted piston or ring land damage include:

• Erosion at the piston crown is visible.

• Melted areas can be seen at the piston crown (Fig. 1) – right up to a completely melted off top of the piston (Fig. 2).

• In extreme cases, there are seizure marks all along and around the piston. There is a hole in the piston.

PROBABLE CAUSES

This damage is attributed to the thermal overload of the piston. There are two causes for this.

Abnormal combustion can be diagnosed via the following features:

• The bowl edge has been “gnawed off.”

• The injection nozzles display a poor spray pattern.

• The injection pressure and the delivery rate of the injection nozzles are set incorrectly.

• The top land shows seizure marks in the piston pin axis.

An abnormal combustion can be caused by a number of factors such as if the air-fuel mixture in the combustion chamber is too rich. This can be the result of the following:

• The air supply is reduced, e.g. the air filter is clogged.

• The fuel delivery is set incorrectly.

• The start of fuel delivery is set incorrectly.

• The nozzle needle is either wedged or stiff.

• The exhaust gas system is clogged.

 

There is ignition delay and misfiring, which may be caused by:

• The incorrect fuel or fuel with an insufficient cetane rating is being used, or there is gasoline in the diesel.

• The valves are leaky, resulting in compression loss.

• The protrusion is too small (i.e., there is insufficient compression).

• The air pre-warming is defective (especially for very low ambient temperatures).

Overheating of the piston crown can be identified via the following features:

• The combustion bowl is not damaged.

• An excellent spray pattern can be observed at the top of the piston.

The excessive temperature level of the piston crown can be caused by:

• The cooling oil nozzle is either bent, has become detached or has not been assembled (assembly error).

• The time between oil changes is too long. In this case, there is a risk of polymerization of the engine oil, especially when using biofuels, such as rapeseed and soybean oil, which can result in the cooling oil nozzles being clogged.

• Contamination, such as gasket residue, etc., prevents the required circulation in the oil circuit.

SOLUTION

• Set the injection amount and timing according to the manufacturer’s specifications.

• Check the injection nozzles for any leaks, the injection pressure and the spray pattern.

• Pay attention to correct alignment when assembling the cooling oil nozzles.

• Thoroughly clean the oil channels in the engine block, the crankshaft and the cylinder head.

• Make sure the pressure-regulating valve is functioning correctly.

• Ensure that the time between oil changes is much shorter when running the engine on biofuels.

–Tech Tip courtesy of MAHLE Clevite 

fig. 1 - melting at the top land of a diesel pistonFig. 2 - Melted piston crown at a diesel piston

You May Also Like

Jesel Certified Performance Rebuilds

Engine components are serious investments for any racer and maintaining that investment could be the difference between winning a championship and losing it.

Now that the race season is over, it’s a great time to freshen up your engine. Many shops are calling on their race customers to get a jump on that rebuild work before things get crazy again quickly in early 2023. One rebuild service folks with Jesel components might want to consider is taking advantage of Jesel’s CPR department to inspect, update and rebuild your Jesel rockers, lifters and followers.

Going the Extra Mile with Cylinder Head Porting

It’s not just the port work alone that creates spectacular cylinder head performance. The most critical areas of a cylinder head are those which pass the most air at the highest speed and for the longest duration. Your bowl area, the valve job, the throat diameter, and combustion chamber are all crucial parts. 

Tight Tolerances and Building Power

As you ascend Mt. Everest, you reach an area called the death zone. Once you climb high enough, the margin of error becomes perilously thin. That death zone also applies to engines. As the horsepower per cubic inch and rpm increase, the margin of error decreases. 

CNC Update: Features and Automation

Precision is key when it comes to automotive parts; the complex designs of connecting rods, pistons and rings, blocks, cylinder heads, and other parts require super tight tolerances that are getting more and more difficult to be met by hand or with other machining processes outside of CNC.

All Things Media Blasting

Engine building is a segment of the automotive industry that has always been ahead of the curve in media blasting, and no matter the engine shop, cleaning equipment is a common bond.

Other Posts

Engine & Hub Dynos: Necessary Tools and Additional Revenue

Being able to see the horsepower and the direct correlation to what is lost in the driveline is invaluable – dynos offer a myriad of benefits for the modern engine shop.

November 2022 Shop Solutions

November tricks and tips for the shop!

Shop Solutions October 2022

When machining on the CNC mill, it’s necessary to blow the flood coolant and chips off the parts for inspection. I tried a tool holder mounted fan, but it wouldn’t get all the chips and coolant out of the deeper areas.

Could Engine Oil Soon Contain No Oil?

The trend towards ever thinner engine oils is an effort to reduce fuel consumption and emissions. How far can it go?