Is your car creating a rattling noise after you start it at the beginning of the day? Perhaps the noise goes off after about 30 to 60 seconds. In this article, I’ll discuss engine rattle on startup then goes away – what to do.
If your car is acting this way, it may be because the bearing on the starter pulley is already failing. During startup, the bad bearing will create rattling noise, which typically goes away after it is lubricated by oil or after it heats up and slightly expands, making it run quieter and smoother.
There are other reasons your engine can make rattling sounds at startup, which goes away shortly. It may also be because the pulley belt is already worn out. To determine the real cause of the noise, you need the help of a qualified mechanic who can pinpoint the exact reason and apply the proper fix.
Read on to learn more about why your engine makes rattling noise during startup, which goes away shortly after, and what you can do about it.
Engine Rattle on Startup, Then Goes Away
Any strange sound coming from the engine should not be taken for granted. Your car and engine should run smoothly and as silently as possible.
So, if you hear a rattling noise from the engine after just starting it and the sound goes away shortly after that, you should not shrug it off because it doesn’t mean your car is just fine.
No, it’s not fine. Your car has an issue you should attend to immediately – if you don’t want the problem to worsen.
One of the usual causes of this problem is the main crank bearing of the starter pulley. Perhaps it is starting to go bad. However, the noise goes away because the engine is running after about 30 to 60 seconds.
The oil has had enough time to lubricate the noisy bearing. This makes it run smoother and quieter, so the rattling noise it makes at startup begins to fade off shortly after that.
Worn-out pulley belts could also cause it. The starter pulley uses a tensioner belt or an idler, which can deteriorate over time. If this belt is already frayed or overstretched, it could slacken off and create strange noises while the engine runs.
Since many things can cause this issue, it is essential to isolate the real reason why your engine is acting this way. You will need a qualified mechanic to properly diagnose the cause and recommend the proper fix so you can put this issue behind your back as soon as possible.
Why Does Your Car Make a Noise When You Start It and Then Goes Away?
There are several reasons why your engine is acting this way. I have tried to isolate the typical and the not-so-typical causes of this problem. This section will discuss them in detail. So, let’s dive in:
1. Lack of Lubricating Oil
Bearings rotate smoothly if they are sufficiently lubricated. Oil can only lubricate the rotating parts of a vehicle if they flow at the correct pressure. This pressure will drop if you park your car overnight.
Typically, engines are equipped with oil filters with check valves. These valves prevent lubricating oil from draining back to the oil sump down the belly of the engine.
What happens occasionally is that, for some reason, this check valve fails to seal or close completely, thereby allowing all the lubricating oil to drain back to the oil sump.
That’s when you will have this problem of rattling noise. So, oil circulating while the engine runs will drop from top to bottom. The engine oil that lubricates the metal components will drop to the bottom draining out the oil from the parts that remain on top. That includes the bearings.
It will take a few seconds to bring them back to circulation once you start the ignition and run the engine. This will happen each day when you start your car in the morning after parking it overnight in your garage. You will notice this often when driving a vehicle with high mileage.
2. Pre-Ignition of the Engine
There are times when your engine will pre-ignite. This means the air and fuel mixture inside the combustion chamber is ignited prematurely or explodes before the right burning time.
It happens because of the heat of compression created as the pistons move up during their compression stroke.
This situation creates the same rattling sound coming from the engine.
3. Piston Slap
When the clearances of the engine cylinders and the pistons are no longer tight, the engine will experience what is called Piston Slap.
If the engine’s condition is already such, the pistons will rock from side to side of the cylinder walls at a slight angle instead of going up and down smoothly.
You will experience this problem if your car’s total mileage is more than 150,000 or 200,000 miles. As such, your engine and its components are physically wearing out. They can no longer perform as they did before.
You need to correct the clearances and tolerances of your engine. Only a good engine rebuilder with a good lathe machine can do this delicate and complicated task. You must spend a lot to bring your old engine to its proper tolerances and clearances.
4. Sticky Valve Lifters
Engine noise produced by cold starts is also commonly caused by sticky valve lifters. They usually call this issue an engine “knock.” This happens when the engine valves have lifters that are so sticky that they have a hard time lifting the valves.
Such a condition can exist in an engine if the vehicle owner has used the incorrect grade of engine oil. The manufacturer of every engine of every vehicle ever produced on this earth has their precise recommendation of the engine oil that should be used on the engines they produce.
Not following their recommendation is the usual reason for this sticky lifter issue. You need to follow the recommended oil grade for your engine. It defines the correct oil viscosity that will enable your engine to operate efficiently and without any problem.
5. Worn Out Main Bearing
When you start your engine, the main crank bearing is the first part required to move the engine. So, this bearing does a cumbersome job of turning over a dormant engine for the first time every morning.
Over time, this bearing will wear out considerably, especially if the vehicle’s mileage is more than 150,000 miles. There will come a time when it shows signs of aging and stress.
And this is when you will hear rattling noise whenever you start your engine after you have parked your vehicle overnight.
6. Worn Out Engine Components
All vehicles have different engine attachments to make them run efficiently and smoothly. If any of these accessories develop any issue, it can also cause the engine to rattle at startup. So, keeping an eye on these accessories and seeing they are well-maintained is also essential.
What are these car accessories? They include the following:
- Power steering pump
- Water pump
- Exhaust manifold
Be aware that many of the noises produced by these engine accessories are considered normal – until they develop more severe problems. So, you need to immediately diagnose the exact cause of the engine noise before they develop into troubles that are more difficult and more expensive to fix.
Again, why does an engine rattle when you first start it but then go away? An engine usually rattles but then goes away due to a worn engine, faulty bearing wear, sticky valve lifter, piston slap, or oil-drain back.
What to Do If You Hear a Rattling Noise in Your Engine?
Thankfully, there are many things you can do to fix this problem yourself. However, for more severe and complicated issues, you have to ask a certified mechanic or an established car repair center to resolve the issue.
Here are some things that you can do yourself:
1. Allow Your Engine to Heat Up
Start your car and let its engine heat up for a few minutes. If the oil drain caused the issue, this action would circulate the oil to the engine part, which creates noise. Hopefully, this will “silence” that noisy part and fix your problem so you can drive your car as before.
2. Bring Your Car to a Service Center
To fix this rattling noise problem, you must check the condition of the part that creates the noise. This will require the expertise of a certified mechanic. The best thing you can do is to bring your vehicle to a car service center that you can trust.
The mechanic of this service shop will thoroughly inspect your vehicle about what you are now experiencing. They have the tools and experience to diagnose and appropriately fix your engine’s rattling noise problem.
How to Repair an Engine That Rattles During Startup
If you want to know some of the fixes for specific causes of this problem, keep on reading:
1. Replace the Problematic Lifter
If this problem reoccurs after some time, you must replace the problematic lifter or lifters. Only a certified car service shop can do this kind of engine repair.
Be aware that the typical recommendation of car repair shops is to replace all the lifters, even if only one or two have problems.
2. Lubricate the Bearing
If the bearing causes a rattling noise, ensure it is adequately lubricated with engine oil. So, it would be best to monitor the engine oil level. See to it that you follow the manufacturer’s recommendation regarding oil level.
If the mechanic finds out that the noise can be traced to a small leak in the exhaust manifold, allow the engine to heat up. This will also heat the exhaust manifold, hopefully sealing the leak and silencing the rattling noise.
If the leak is large, you must let a muffler repair tech fix and seal the leak. That’s the only way you can correct this issue.
Your car may be creating rattling noise because the bearing on the engine’s starter pulley is going bad. Perhaps it is already wearing out.
When the engine starts, the engine oil will begin to lubricate the old bearing, and it also starts to heat up. This causes the noise to disappear after about 30 to 60 seconds of starting your car.
There are other reasons for this problem as well. You have to pinpoint the real cause of the issue so you can apply the proper fix. The best way is to ask the help of your trusted mechanic to diagnose the problem and recommend an appropriate fix.