Valves and piston rings are crucial for your engine to function properly.
Aside from your head gasket, these are the parts that are responsible for sealing the combustion chamber.
Most of the time, valves and piston rings will give you warning signs, long before they actually fail.
Although bad valves and piston rings have similar symptoms; the time and costs of repairing them are quite different. Valve problems are a sign of serious issues with your engine. The intake and exhaust valves rely on physical contact with the valve seat and guide for cooling.
So, anything that interferes with valve cooling or creates extra heat in the valve or head; can lead to premature valve failure. Furthermore, properly sealed valves are crucial to your engine’s compression. Problems with your engine’s piston rings often display symptoms; or signs that are similar to other problems with low compression in a engine.
Healthy engines should have compression over 100 psi per cylinder; with no more than 10 percent variation between the highest and lowest readings.
But First, What Are Their Functions
Piston rings are located between the piston and cylinder and provide four different functions:
- The ring creates a seal, preventing combustion gasses from leaking out of the cylinder. Leaks can drastically reduce engine performance.
- Every time combustion occurs, the internal temperature of the cylinder spikes. These high temperatures can cause serious damage. As a result, piston rings help transfer this excess heat from the piston head to the cylinder; reducing the risk of heat damage.
- A film of oil is necessary to keep the piston lubricated. Piston rings help regulate the amount of oil that reaches the piston.
- The piston works on a crank and could easily bang into the cylinder wall; if not for the piston ring’s padded support.
It is important to note that piston rings do wear out; which means you’ll have to replace them at some point.
You rarely hear about valve problems in cars nowadays; because modern overhead camshaft engines have fewer components, to break down and cause problems. In the past, several components, such as non-hydraulic lifters, push-rods, springs and the valves themselves, all could go bad.
You may have heard the term “getting a valve job” because older cars, frequently needed their valves adjusted. If you have an older car, you may still have some of these problems. In contrast, modern cars valve trains that are virtually trouble-free.
There are four strokes that must take place in your engine, to ensure proper operation.
1-The first stroke is the intake stroke.
- During the intake stroke, an air/fuel mixture is drawn into the combustion chamber; by opening of the intake valves. NOTE – (with direct injection engines, the fuel is injected after the air has been drawn in).
2-The next stroke is the compression stroke.
- Both the intake and exhaust valves close; trapping the air/fuel mixture in the combustion chamber. The piston is now forced upward compressing the air/fuel mixture; causing it to become highly combustible.
3-The next stroke is the power stroke.
- The compressed air/fuel mixture is ignited by a spark plug. With the exhaust and intake valves remaining closed, the ignited mixture rapidly expands; forcing the piston back downward in the cylinder. This in turn spins the crankshaft; which then through the powertrain eventually turns the wheels of the vehicle.
4-The final stroke is the exhaust stroke.
- During the exhaust stroke, the piston will begin to head upward again; pushing the expended mixture through the now open exhaust valve. After the exhaust gases have escaped the cylinder; the exhaust valve will close and the intake stroke will occur again.
Failure Warning Signs Of Bad Valves And Piston Rings
The symptoms of bad valves and piston rings are quite similar. Whenever either fails, the performance of the vehicle will drop, and other symptoms will manifest.
Let’s take a look at some warning signs that these components are going bad:
If you notice thick smoke that’s blue-gray or light-gray; this is a good indication your car is burning oil. It’s a sign that oil is leaking into the combustion chamber of your engine.
Generally, the amount of blue smoke you see, with valve guide and seal failure; is fairly small and barely noticeable. If you are spewing out a large amount of smoke, then you may have more serious problems; such as worn valves or damaged piston rings.
Excessive Oil Consumption
As mentioned above, if the piston rings are worn out; oil will begin to leak into the combustion chamber. This causes your engine to use up its oil supply much quicker.
When there is damage to the valves and piston rings, compression will be reduced. This causes you to lose engine power. As a result, you won’t be able to accelerate when you put your foot on the gas pedal.
Burnt valves are another problem that contributes to power issues. Many things can cause burnt valves, but one of the most common reasons is ignoring leaking seals and guides; or failing to fix other compression problems.
Ticking noises are the most common types of noises you will hear; when you’re having trouble with your valves. This noise gets louder and faster as the engine is accelerated. It usually means that some of the valve train components are either worn or out of alignment.
Testing Valves and Piston Rings
You can do a compression test and cylinder leak down test to help pinpoint the problem. Low compression usually indicates that the piston rings are your problem. To further confirm worn piston rings are the problem, do a wet compression test. Here you remove the spark plug and inject a bit of oil (about a tablespoon) into the cylinder. If the compression increases, your piston rings are bad.
A cylinder leak down or cylinder leakage test is similar to a compression test in that; it tells you how well your engine’s cylinders are sealing. But, instead of measuring pressure, it measures pressure loss.
A cylinder leak down test requires the removal of all the spark plugs. The crankshaft is then turned so that each piston is at top dead centre (both valves closed); when each cylinder is tested. Most people start with cylinder number one and follow the engine’s firing order. A threaded coupling attached to a leakage gauge is screwed into a spark plug hole. Compressed air (80 to 90 psi) is then fed into the cylinder.
An engine in great condition should generally show only 5 to 10% leakage. An engine that’s still in pretty good condition may show up to 20% leakage. But, more than 30% leakage indicates trouble.
The neat thing about a leakage test (as opposed to a compression test) is that; it’s faster and easier to figure out where the pressure is going. If you hear air coming out of the tailpipe, it indicates a leaky exhaust valve. Air coming out of the throttle body or carburetor would point to a leaky intake valve. Air coming out of the breather vent or (PCV) valve fitting; would tell you the rings and/or cylinders are worn.
So, valves and piston rings problems are something you should not ignore. However, they are easy to prevent, or at least delay, with proper engine maintenance. Finally, have your oil changed regularly, and fix any other engine problems promptly.
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