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This problem is mainly caused by carbon buildup, sticky lifter, worn-out bearing piston slap, and worn-out engine parts. There are probably more, but these are well-known causes. There are a couple of reasons why your car engine knocks on a startup.

First, if you start hearing the noise as you start the car, but as the car warms up, the noise gradually stops. These problems can be overwhelming when they occur and could make you panic when you don’t know what to do.

What Are The Causes Of Engine Knock On Startup?

Although you are not a professional, you can easily detect these causes: piston slap, sticky valve lifter, worn engine, worn bearing wear, and oil-drain back. Here are some of the causes of engine knock on startup then goes away.

1. Piston Slap:-

When your car is old and gets to 180,000 miles, there’s a high tendency for piston slap issues to surface. Piston slap is the loosening up of the piston from the cylinder wall when they are no longer adequately fitted together as they should be. Age is a factor in this because intolerance will increase as the component wears off.

This can alter the movement of the piston; instead of moving up and down, it will start moving in a rocky or shaky way. This problem may result from the design flaw and not tear and wear in some cases.

2. Sticky Engine Lifter:-

Your car engine may knock on startup because of these lifters. In addition, there’s a loud ticking sound distinct from other engine knocks, which is usually caused by a sticky engine lifter. The most common cause of sticky valve lifters is poor oil lubrication. Hence, the sticky engine lifter problem will be solved if proper and good oil lubricant is used.

When your car has covered hundreds of miles, it may develop such a problem because the engine oil cannot control such gaps, leading to poor lubrication and mechanical fault that comes with an awkward sound.

3. Worn Engine Parts:-

Engine knock on startup then goes away can happen because of worn-out engine parts such as alternators, steering pumps, and water pumps. The car will function correctly until a particular part fails, at which point the check engine light will illuminate. You will experience a rhythmical and harmonic noise from the worn engine part, but the noise will gradually die off as soon as your car starts up.

This is because the engine oil is circulating through the parts when the car is warmed up. The heat will help expand the bearing, and there will be a proper operation of the car irrespective of the wear.

4. Bearing Worn-Out:-

The function of a bearing is to help rotational parts of the engine move properly. Without it, the engine won’t be able to work correctly. For example, the engine will start producing sounds if they get worn out, causing the engine to knock on startup. Engine slap can also happen as a result of worn-out bearing.

The main crankshaft bearing is the most affected, causing a disconnection between the crankshaft and other engine parts. When the crankshaft is heated, the issue disappears and resurfaces when the temperature drops.

5. Oil Drain-Back:-

When your engine block drains oil through the check valve. If your check valve is faulty, the engine block won’t be properly sealed, allowing oil to leak from the oil filter. In this case, the oil pump is forced to pump oil into sensitive parts that are not designed to handle oil.

As a result, you will keep hearing the knocking sound for a minute till the oil is pushed into the engine parts and thoroughly lubricate the parts. Though this problem will disappear after the engine is warmed up, the sound issue will still surface on startup.

6. Carbon Buildup On Engine:-

As your car starts getting old, it starts building up carbon in the engine. This is because the engine no longer performs complete combustion, producing black soot. This buildup will cause the hardening of the engine parts, which is very unhealthy for your engine.

How To Fix The Engine Knock On Startup Issue?

Here are some steps through which you can easily fix this issue of engine knocking out on startup:

Step 1:- Keep An Eye Out For Wear And Tear On The Cylinder And Piston

Firstly, locate the engine by opening the engine bay. Get a mechanical toolbox and also get tools like screwdrivers and wrenches. Then start dismantling the engine to gain access to the cylinders and pistons. Take a very close look at the piston and walls of the cylinder. Keep an eye out for wear and tear on the cylinder and piston.

If you notice the design is flawed too much and can’t be fixed by replacing the faulty component, you either carry out a piston-cylinder rebuild or call an expert to do it. Know that it is an expensive procedure and best done by an expert.

Step 2:- Examine The Engine Lifters

Unlock and open the engine bay, then locate and examine the engine lifters with your eyes. Take note of how long it takes for the engine knocks on startup to fade away because that will help ascertain why the engine lifters are faulty.

Step 3:- Examine The Components

Examine the component for signs of wear and tear because the part may have been affected by the prolonged noise. Examine components like valve lifters, springs, and pushrods. Ensure that they are correctly fixed because they can cause sticky valve lifters if they have poor attachment and tolerances.

Step 4:- Look Out For Proper Oil Viscosity

After examining the above and everything is in good condition, the problem is from the engine oil. Get proper engine oil with the right properties and viscosity suitable for your vehicle. Examine the parts and see if there’s poor lubrication and if the lubrication level is low because the engine part’s wear could result from your car leaking oil when parked. Get a replacement for the worn-out parts and make sure there is good and enough engine part lubrication.

Step 5:- Examine The Bearings And Crankshaft

Open the engine bay and examine the bearing and crankshaft. Inspect the bearings for wear and crankshaft tolerances for deviations. You also need to check the oil conditions of the bearing, and ensure that it’s okay because poor bearing lubrication can lead to bearing failure.

Step 6:- Check The Oil Filter

Check the oil filter and examine the check valve to ensure it is securely fitted. When you notice oil on sensitive parts where oil shouldn’t be, it’s a clear sign of an oil drain back problem. Buy and replace the oil filter to protect the oil in the engine block. Ensure that you purchase the original oil filter with quality check valves.

How Much Does It Costs To Fix This Issue?

The cost of fixing engine knock on startup then going away is quite expensive, and it could be as low as $2,000 or more or as high as $5,000 or more. The cost of cleaning the engine can range from $250-$500. It depends on the price of parts, location, labor cost, price of buying and changing oil, and flaws associated with design.

How To Prevent Engine Knock On Startup Issue?

As earlier stated, this issue can be caused by a couple of reasons, such as wear and tear of engine components or piston slap. When you notice such symptoms, please ensure to visit your mechanic for proper diagnosis because if you allow the problem to persist, you are signing in for a bigger problem. The earlier you resolve the issue, the better.

Below are suggestions on how to prevent your car from experiencing engine knock on startup issue.

1. Invest In High-Quality Oil:-

Good quality engine oil can reduce engine wear and tear. Each time you start your car, it will get hot quickly. It means the engine parts broaden fast, causing friction among metal parts. This can damage the engine if lubrication is not ensured properly.

The oil with high-quality assists in improving the engine performance by decreasing heat generation and lengthening the life of engine parts. Moreover, it can clean up wear particles, remove carbon deposits from engine valves and pistons, and stop engine noise on startup.

2. Get Your Engines Tuned Regularly:-

Taking your car to an appropriate engine tuning service helps avoid engine knock-on startup. They ensure that the engine is performing smoothly without any obstacles such as carbon build-up or misfiring. Regular checkups for your car can enhance the overall performance by making improvements, for example, adjusting the time of spark plugs, setting the air/fuel ratio, etc.

3. Change Filter Constantly:-

Dirty and old engine oil can cause sludge build-up, which impairs the engine performance. Therefore, changing the oil filter regularly is a must to ascertain the engine oil remains pure and engine components are properly lubricated.

4. Never Ignore Check Engine Light:-

Another method to prevent a knocking sound when starting your car is noticing any warning signs of the engine light. Whether it is a normal check engine light or sputtering, ignoring these symptoms can bring many problems or engine damage.

5. Avoid Driving Rough:-

You should limit the time driving aggressively if you want to prevent engine wear and tear. This type of driving involves speeding up or revving your car when you are in traffic jams. As constant high speeds equal faster wear, one of the main factors causing piston slap on startup and damage to other engine components.

Frequently Asked Questions:-

Let us now see some frequently asked questions such as does loud knock when starting car disappear? how much does it cost to repair the engine knock? etc.

1. Does Loud Knock When Starting Car Disappear?

Yes. When the engine is warm enough, this knocking sound will stop. However, even after the noise has decreased, the engine has been harmed, more or less. Due to this, it is important to ask the mechanic’s opinion if you hear any strange noise from your car.

2. How Much Money Does It Take To Repair Engine Knock?

The cost of doing this is not also pocket friendly, and it could be as low as $2,000 or more or as high as $5,000 or more. The cost of cleaning the engine can range from $250-$500.

3. How Long Will Your Car Last With Rod Knocks?

Six months is the longest period that a rod knocking engine can endure before it blows up. However, using an engine with a rod knock is not good because it can cause more damage and shorten its lifespan.

4. Is Engine Knock Worth Fixing?

Conclusion:-

We have seen some reasons, their solutions and how to prevent your car from this issue of the engine knock on startup then goes away. The best approach is to carry out regular maintenance to help adjust engine components when necessary, clean up soot and dirt, and give a general healthy working condition in your car engine to prevent this problem from occurring.

We hope the above-mentioned information will be helpful to all the readers. If anybody’s doubts persist feel free to comment in the comment section below. We’ll try to solve your doubts as soon as possible.