Piston problems can mean anything from eroded piston head or skirt to worn piston rings and pin. These usually lead to power issues. The problems can also cause a severe breakdown of engine parts. When attended to on time, piston damage is easy to take care of and avoid engine destruction. Read to understand the problems to look out for, piston symptoms, and the ways to deal with each.
Common Piston Problems
The piston resides in an environment where temperatures and pressure levels are insanely high. In order to prevent damage, the modern piston for car engine application is made from high quality materials. In spite of that, the various parts of the assembly do fail either due to age or harsh conditions.
The most common piston problems are:
- Piston crown damage
- Piston rings failure
- Piston skirt damage
- Piston pin, bolt, and bearing damage
Piston Head Damage
The piston head is the part that comes into contact with hot gases in the combustion chamber. Despite being made from a strong material, the head or crown, as it’s also called, often gives in if conditions are too harsh. The causes for piston crown damage include:
- Excessive heat due to incorrect fuel grade or spark plug
- Incorrect engine timing causing the crown to hit the valves
- Faulty engine cooling system or bad detonation sensor
- Using the wrong type of piston or cylinder head for the engine
- Low oil levels causing excessive wear and seizing
A damaged piston head will have a pitted or scuffed surface, melted parts, or eroded edges. It may even contain visible hole or depression and visible cracks. The crown is one of the most important parts on a piston. If damaged, the piston must be replaced.
Piston Rings Failure
Different types of piston rings provide different functions such as sealing the combustion chamber, conducting heat away, and wiping off excess oil from the walls of the cylinder. The rings can get damaged, often as a result of wear or deformation. The main reasons for piston ring failure are.
- Incorrect piston installation procedure
- Worn piston grooves
- Fuel flooding
- Inefficient combustion
- Wear by particles present in oil and other debris such as chips from a milling process
Damaged rings will not adequately seal the combustion chamber, causing piston blow-by. Lubricating oil will also leak down the walls of the cylinder and cause increased friction between the piston and cylinder bore.
Damaged rings will show visible signs of wear. To detect wear, a compression or leak down test is normally performed. Bad piston rings can cause engine issues. Luckily they’re replaceable as separate parts. This is one of the repair options when you have a failing piston.
Piston Skirt Damage
The skirt aligns the piston, balancing it inside the cylinder bore as it moves. This prevents the piston from rocking about and causing problems. Piston skirts can wear or deform with time and cause problems. Some of the reasons for piston skirt damage are
- Using an incorrect piston size
- Fuel flooding
- Excessive friction that leads to wear
- Pitted cylinder walls
- Excessive rocking of the piston assembly within the cylinder
- Bent conrod or excessive rod bearing clearance.
Upon inspection, a damaged skirt will have eroded surfaces to indicate wear or some parts may appear deformed due to impact. You can also tell a damaged skirt by measuring the piston cylinder clearance to see if it’s out of specification.
If a piston has a worn or collapsed skirt, replace it. The problem usually causes engine horsepower to drop. That’s in addition to risking damage to other engine parts that would cause you repairs and replacements.
Piston Bolt and Bearing Damage
These parts take the beating during piston operation. The pin is the pivoting point for the piston rod, while the bolts have to endure the mechanical stress as the piston rotates the crankshaft. Piston bearings have to stand up to wear as the crank rotates. Damage to the parts occurs due to:
- Inadequate oil supply
- Mechanical stress caused by the working of the piston
- Incorrect piston installation
- Normal wear and tear
All the mentioned parts are replaceable. In severe situations though, it’s more advisable to replace the entire assembly. That’s because piston wear or damage usually happens after many thousands of miles and only changing some parts may not provide the desired results.
Piston Failure Symptoms
Piston problems cause observable symptoms. Being part of the engine, most bad piston symptoms appear as power issues. The engine is costly to fix or replace. As such, it’s crucial that you be alert to the signs that a piston is damaged. Common ones are listed below.
Reduced Engine Power
The engine loses power and accelerations are difficult. This usually results from decreased compression caused by a bad piston or pistons. Most often, the rings are worn and causing the combustion chamber to leak. You can choose to change the rings or replace the piston depending on the situation.
This is one of the signs of piston ring failure. The engine frequently misfires due to reduced compression. Reduced compression, in turn, comes about when the rings cannot seal the combustion chamber properly. It’s not every misfire that’s a piston misfire, though. There are many other causes. Check the pistons and replace them or the rings if you find them to be the culprit.
Excessive Consumption of Oil
You notice that you have to replace the engine oil too soon. Again, this sign mostly indicates piston ring damage. The rings are too worn and causing the clearance between piston and cylinder to widen. When that happens, the oil leaks freely down the cylinder walls. This problem is easily corrected by replacing the affected rings but mostly by installing new pistons.
The smoke coming out of the exhaust pipe is thick and bluish or light gray. It’s usually an indication that oil is burning in the cylinders due to worn rings or cracked piston head. The problem results in the oil getting into the chamber, burning up in the heat, and exiting via the exhaust valve. You may choose to replace the rings or piston. For a cracked head, you can only install a new piston.
There’s noise coming from the engine, especially during idle speeds. This is commonly caused by the piston knocking against the cylinder bore, popularly known as piston slap. It means an excessive increase of piston and cylinder clearance often due to skirt or ring damage. Piston slap when cold or immediately after engine start should not be a major issue. It should go away once the engine heats up and the piston expands. If it doesn’t, consider fitting new rings or changing the piston.
Check Engine Light
A dashboard light comes on to alert you of an engine issue. Although caused by many different problems, the light is one of the earliest symptoms of bad piston or pistons. Reading the generated trouble codes then points to the source of failure. In most cases, it will be misfire caused by reduced compression. Change the piston or fix it by replacing the rings.
Piston problems are a risk to your car engine but not when attended to as soon as you notice them. Based on the piston failure symptoms in this section, find out when the ones in your car engine has gone bad and take the necessary steps such as repair or replacement. In the next part, you will be learning the procedures to diagnose pistons through tests and inspections.