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What Are the Signs of Failed Valve Seals?

It’s always a good idea to be prepared and learn about the signs of failed valve seals in order to prevent future issues. Read everything you need to know below.

What Are the Signs of Failed Valve Seals? - KB Delta

There are several signs of failed valve seals and being wary of these symptoms could help you avoid potential problems that could arise if a quick fix is not made.

First off, valves aid in the regulation of a system, and they are used in industrial processes such as water & sewage processing, food manufacturing, mining, power generation, etc.

Valves also have seals whose design makes them compatible with various engines. The design of these seals determines the component’s performance and longevity. Seals are used to control oil consumption and to aid valve lubrication.


The Function of Valve Stem Seals

Valves stem seals help to regulate the amount of fuel mixture that enters the cylinder. The valve comes with a seal and in some cases, a protective sleeve.

The seal prevents the leakage of combustion gases. It also disallows the leakage of oil into the main engine area. As the seals degrade, you may begin to notice certain symptoms that are peculiar to faulty valve seals.

Accordingly, here are some signs of faulty valve stem seals to keep you informed of any possible issues that may arise.


Signs of Failed Valve Seals

Some of the top signs of failed valve seals are:

1. Cold Engine

A cold engine test will help you know if you have bad valve seals.

For instance, you may have left your car overnight or for a long time, and the top of the valve’s headcover may still have some oil from the last time the car was driven.

However, when the engine is started, the oil may be sucked down through the bad seal and then into the combustion area. It could end up with a blueish smoke out of the tailpipe.

If you notice this, then you need to get a new valve seal since the latter is evidence that you have a valve that has not been securely sealed.

2. More Oil Consumption

A good sign of a bad valve seal is high oil consumption.

If you notice that you’re running out of oil faster than usual, it’s possible that the oil is leaking out or burned too fast. The oil leaks into the combustion chamber because the valve seal is broken or the piston rings are worn out.

Thus, it could cause the oil to decrease faster than usual and even lead to the creation of excessive smoke.

So, how can you tell that there is a high level of oil consumption? It’s by using a basic dipstick and keeping track of the oil levels.

The valve seals may still be bad even if you can’t see any noticeable oil leaks.

3. Idling

You can test a bad valve seal by monitoring how your car operates when it is idling.

A car that is at rest for a long time may have oil buildup around the valve system while it is closed as a result of high vacuum levels. If the valve seal is faulty, the oil may get sucked past the seal into the valve guide as you start accelerating from a stop.

More blueish smoke will be given off from the tailpipe as a result of the burning of the oil. The smoke will tend to disappear while cruising or on highway speed.


What Are the Signs of Failed Valve Seals? - KB Delta


4. Engine Braking

Engine braking describes measures other than external braking are used to slow down your car within the engine.

In the case of a faulty valve seal, the oil that accumulates at the front cover of the head may burn when the accelerator is pushed after you’ve driven for a while.

The latter might be evident when driving downhill and will also be indicated by the excessive smoke that escapes the tailpipe.

5. Compromised Acceleration Power

If your vehicle lacks acceleration power, then it is an indicator of a faulty valve seal.

Accordingly, conduct a compression test to ascertain if the problem is caused by a bad valve seal or piston ring. It is a valve problem if the compression level is high while it is a piston ring problem if the compression level is low.

You’ll also do well to learn the differences between both components since they have similar faulty symptoms.

6. High Levels of Smoke

A good indicator of a faulty valve seal is high levels of smoke being given off.

Usually, exhaust smoke is produced from your vehicle when it’s first turned on, however, if the smoke is more than usual, you may be dealing with a faulty valve seal.

Keep in mind that oil burning can also cause an excessive amount of smoke, but this time, produced in waves.

7. Off-Throttle Braking

Symptoms of bad valve seals will present themselves during off-throttle braking. The issue will be evident when going down a steep downgrade where the accelerator pedal is static.

With the creation of the high intake manifold vacuum, as well as, the downward slant of the engine, the oil will collect towards the front of the valve’s cover over the head.

As the accelerator is pushed after a long coast, oil burned will leave the tailpipe in large amounts.

What’s more, the engine will keep burning the oil longer but it will not be a permanent condition until the stop of the smoke under normal cruise.



These are the signs of failed valve seals you should be on the watch for.

These signs of bad piston rings or valve seals may not be evident today, but they could spring up at any time. Being able to identify them quickly ensures your vehicle still functions properly after a replacement of the valve seal.

It’s even better that you can spot a faulty valve seal immediately you detect the symptom. Therefore, keep these signs at the back of your mind and get your vehicle the immediate repair it requires.


What Are the Signs of Failed Valve Seals? - KB Delta

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