A car engine can make various noises including humming, droning, growling, or rattling temporarily during start due to plenty of reasons. If your car engine rattles on startup then goes away, it can be a result of a faulty timing chain, bad exhaust system, loose brackets, or damaged oil filter.
You can keep driving for a while with engine rattling issues. However, it’s better to repair or replace the faulty part to avoid causing serious issues.
Article Summary
Why Does My Car Engine Rattle on Startup Then Goes Away?
A car engine can make a rattling noise for a few seconds before starting the engine or a cold start-up due to these reasons:
1. Faulty Timing Chain
If your car engine rattles on startup and then goes away, it can mostly result in a damaged timing chain. The timing chain operates the camshafts and crankshafts. It rotates them properly to keep the engine running. However, the timing chain can get damaged due to wearing out on the crankshaft and camshaft sprockets.
Though applying lubricate can reduce the wear, it can’t restore the performance. The worn sprockets and timing chain can’t apply sufficient tension and it causes the timing chain to bounce and rattling noise. This rattling noise becomes more noticeable during the start particularly when engine oil pressure is low and the temperature is cold.
2. Exhaust System Vibration
The exhaust system is another common source of car engine rattling noise. Exhaust components like catalytic converters, heat shields, or mufflers can cause looseness or rust. During the start of the engine, the exhaust vibrates and causes the components to rattle. The rattling noise becomes noticeable at a cold start when the metal remains more rigid.
3. Loose Brackets
Bolts, brackets, and fasteners may become loose due to the consistent movements and vibrations that occur during driving. Loose components can make a rattling noise during start-up.
4. Damaged Crankshaft Harmonic Balancer
The crankshaft balancer absorbs and reduces the engine vibration when a crankshaft rotates. It’s made of metal and rubber and placed near a crankshaft pulley.
But, if a crankshaft balance wears out, it gets displaced. Hence you can experience vibration and hear a rattling noise during start-up.
5. Main Bearing Wear
The crank bearing can wear out due to high mileage. If the crank bearing fails, it can hit the thrust bearing continuously. Hence you can hear a rattling noise during engine start-up. When the engine warms up, the rattling noise stops.
However, you can prevent this problem by keeping the engine oil top up. You’ll also have to prevent the bearing from leaving metal flakes in the oil pan.
6. Bad Oil Filter
A car engine can also make a rattling noise due to using a low-quality oil filter. Quick oil changes also damage the oil filter over time. Oil filters are designed with an anti-drain back valve. It keeps oil from draining down out of the galleys after shutting off. During a cold start, oil takes a few seconds to pump back through the passages to reach the moving parts.
Is Engine Rattle On Start-up Normal?
It depends on the engine’s rattle type. If you hear a low rattling noise during idle and it vanishes after revving the engine, you shouldn’t drive the car. It’s concerning as it indicates loose or worn big-end bearings. In this case, you have to replace the engine to fix the problem.
If you hear the noise all the time and if it becomes less noticeable in a warm engine, you can keep driving for a while. This loud rattle noise can be a result of a wobbly cam chain.
In this case, you only need to replace the chain. Changing the chain is cheaper than replacing or rebuilding the engine. You can also adjust the cam chain to eliminate the noise if it’s a manual hit.
If the loud rattling noise comes from under the car, this can be due to a loose exhaust pipe. It’s a normal situation and you can keep driving the vehicle.
How To Fix Engine Rattle Noise on Startup?
It’s quite difficult to fix the engine rattling noise without proper diagnosing. You have to find the exact root first. To find the exact source of the noise, use a PVC pipe, rubber hose, or wooden dowel as a stethoscope. Place one end of the pipe to the ear and use the other end to probe the engine.
Start the engine and ask someone to listen to the source of the noise carefully. Make sure the pipe and hands are away from the fans. Once you find the source, you can easily fix the issue. You can replace the timing chain if the noise comes from the engine front.
However, you may need to repair or replace the A/C clutch, serpentine belt, or power steering pump. You may also use Entweg Automotive Noise Finder to determine the root of the noise precisely.
FAQs
Why Does My Car Makes Noise When Starting Then Goes Away?
If the rattle lasts around 2 to 5 seconds and then the vehicle stops, it can be due to a faulty timing chain tensioner. But if the rattling noise comes and goes, a loose exhaust heat shield can be responsible. If the rattling noise remains consistent at idle, it can be the result of loose pulley bolts.
How Do You Fix The Rattling Noise When Accelerating?
If your car makes a rattling noise when accelerating, check the fluid level of the engine. If the transmission fluid runs low, refill the tank up to the proper level. Then test drive the car to check if the rattling noise goes away.
Why Does A Car Engine Rattle On Cold Startup?
The car engine usually rattles on cold start-up due to the timing chain. It can also happen due to loose bearings or a heavily reduced engine power. To fix the problem, you can use a top-quality oil filter as it can increase the oil pressure faster.
Final Words
If your car engine rattles on startup and then goes away, firstly make sure it’s rattle noise and then determine the root of the source. The reason is that cars make various noises during start and they can come from plenty of sources. Once you find the exact root and source, inform the mechanic so he can repair or replace the faulty part.
