valve seals

Bad Valve Seal Symptoms, Information & Replacement Cost

In Engine by Magnus Sellén2 Comments

valve seals

A vehicle has about 30,000 functioning parts, both large and small.

With so many parts, it should come as no surprise that some parts wear out over time and need to be replaced. The highest concentration of wear in a vehicle is found in the engine. As the engine heats up and generates a lot of pressure, some components inevitably lose their integrity.

Valve seals are one such component that can be adversely affected by the heat and pressure of an engine.

The Function of a Valve Seal

A valve is responsible for regulating the amount of fuel and air entering the combustion chamber of an engine. Since the combustion chamber is under pressure, its contents search for an escape route after each cycle. It is possible that the combustion gases escape into the valves and mix with the fuel. To prevent this, valve sleeves are used. It is also possible that the engine oil circulating through the system is sucked into the valve chamber.

To prevent this, valve seals are used to shut off the passage of the oil. The valve seals are made of high-quality hardened rubber that maintains pressure in the combustion chamber and prevents foreign matter from entering the system. Over time, these seals deteriorate and your engine begins to feel the effects. As a driver, you should be aware of when this happens. Fortunately, there are some signs that can help you detect valve seal failure.

Symptoms of a Valve Seal Failure

1. Residual Oil on the Engine

valve seal replacementA failure of the valve seal is easy to detect when you start a cold engine. When you start your car after a long time, take a look under the valve cover and at the top of the engine head. There should be residual oil there, which must have got over there because of a leaking valve seal. In addition, you will also see a thick white cloud of smoke from your car’s exhaust when the engine is cold started, which largely means that the valve seals of your engine have been damaged.

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However, you will need to look under the bonnet and under the valve cover to see any change. Some people are unaware of this or are simply too lazy to do the work themselves and ultimately shorten the life of their car.

2. Rough Idling

A defective valve seal is easily noticeable when your car is idling. When the car is stationary, the high negative pressure from the intake manifold closes the throttle valve, which causes the oil to be sucked in at the valve stem. As soon as you accelerate, this oil seeps into the combustion chamber because the valve seals fail, and it burns up, causing white smoke from the exhaust.

Keep in mind that this only happens in city traffic or when you stop and move rigorously, as you would in a traffic jam. While driving on the highway, this white smoke disappears.

3. Downhill Braking

When the foot is taken off the accelerator, the intake manifold creates a negative pressure that sucks in the oil, as mentioned above, but this effect is enhanced by the downhill position of the car, which facilitates the movement of the oil towards the front of the engine. As a result, more oil collects at the top front of the engine, and in the absence of a good valve seal, this oil spills into the combustion chamber when you accelerate. Once again, smoke will come out of the exhaust, indicating a failure of the valve seal.

4. Bad Oil Consumption

We know about the role of motor oil in an engine. It helps to lubricate the mechanical components so that they can run smoothly. As such, engine oil circulates continuously inside the engine. If there is a leak somewhere, in this case, a valve seal failure, the amount of circulating engine oil is reduced. This happens until the oil level is exhausted. You will find yourself having to change the oil frequently.

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You might also notice that the oil turns black and dirty faster because it burns. As soon as you are confronted with this problem, book an appointment with a mechanic and have the valve seals checked. If you take ten minutes of your time at the earliest possible moment, you will save yourself time and money in the long run.

5. Too Much Smoke From Exhaust

Initially, when the valve seals begin to deteriorate, the smoke will escape in small quantities and then disappear. However, as the problem worsens, the smoke becomes worse and worse. You will notice that the white smoke lasts longer than before and does not disappear even at high speeds.

If this happens, do not waste any time and contact the mechanic directly. The mechanic will have a clear idea of what to do. He will replace the valve seals for you so that you can continue driving safely.

6. Loss in Acceleration

Faulty valve seals reduce the pressure in the combustion chamber, which directly leads to a lower power output of the engine. Your car will lose acceleration, which could be dangerous when you are driving on a motorway. Fortunately, a loss of acceleration is immediately apparent, so you can’t overlook the damage.

Valve Seal Replacement Cost

Valve seals are made of rubber, so they do not cost a lot of money. They also do not break frequently, so you do not have to worry about having them replaced regularly. Depending on the vehicle, replacing a new valve seal can cost between $40 and $150 for the product.

The bad news, however, is that replacing a valve seal takes a lot of time. You have to expect about 3-4 hours of work, and we know that the labor costs of a mechanic are not cheap. A professional mechanic would easily charge you $100 or more per hour for the replacement. So you can expect to pay about $300-$400 for a simple valve seal replacement.

Hello I'm Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I'm specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I'm here to give you answers to all your automotive questions and I hope that you enjoy our content.

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2 thoughts on “ Bad Valve Seal Symptoms, Information & Replacement Cost ”

  1. Can you please provide a comment and/or a best-guess cause of the following complaint: Smoke at cold start (white-blue) that occurs approximately every second or third day. Smoke lasts approximately 5 minutes. Compression test gives good numbers for all 4 cylinders. (Vehicle is a 1999 Honda CR-v – 2.0 motor). Engine runs fine – no misses, idles fine, good acceleration and no random ‘noises’. Oil consumption is minimal – approximately a litre between regular oil change schedules. Use synthetic oil. IF it has worn valve seals, could you provide an approximation of # of hours to replace them…??? Any help is much appreciated – I’m retired pensioner, so $$ are no longer as plentiful … 🙂 – …. thanks for any help!

    1. depending on the type of engine, should take no longer than 2-3 hours with the proper equipment (VALVE SPRING COMPRESSOR). i had to create my own, using a 12” 1k working load clamp, which i applied to a windowed 4” pvc pipe. wear goggles for your safety! keepers are hard to keep!

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