Can A Bad Serpentine Belt Cause Rough Idle?

A bad serpentine belt causes a lack of power to AC, power steering, and other accessories that get power through it. But can a bad serpentine belt cause rough idle? Yes, a loose, cracked or severely damaged serpentine belt can cause rough idle, car engine stall, squeaking noise while driving and various serious issues.

It can also overheat the engine, activate the check engine light, and show plenty of symptoms. Since you can’t continue to drive with a bad serpentine belt, replace it immediately to avoid damaging the engine. 

How Can A Bad Serpentine Belt Cause Rough Idle?  

A serpentine belt is a crucial part of an engine that helps provide power to various vital components. If serpentine belt gets loose or damaged, it causes rough idle. On older models, a toothed serpentine belt drove camshaft on single and dual-can engines.

Bad serpentine belts could cause erratic running or rough idle on that car. It would also break the valve head, cause piston death, and cause irreparable damage. 

On the latest models, serpentine belt drive water pump, alternators, car AC compressor and power steering. A bad serpentine belt can damage the water pump and over time the engine within seconds. If so, it can damage gasket, mess up the rings on position and cause rough idle. 

A tight serpentine belt can also cause rough idle by putting excessive strain on engine components. The reason is that a tight serpentine belt increases resistance on engine and affects its performance at idle.

Signs of A Bad Serpentine Belt

A bad serpentine belt will mostly illuminate check engine light and trigger some drive-ability issues. However, you’ll need to inspect serpentine belt physically to verify if it’s the source of issue.

1. Cracks On The Grooves

Check for cracks on inside of the grooves when flat side goes around a pulley and the grooves come outside. Serpentine belts can cause lots of cracks due to being cooled and heated. If so you’ll need to replace the belt to avoid rough idle. But if you notice three cracks in a three-inch section, you can continue driving with the belt.

Cracks On The Grooves

2. Squealing Noise

If you notice a squealing noise, it is an indication of a stretched serpentine belt. It can make squealing noise due to slipping, low installation tension, extreme wear or being stretched. To verify, check the belt from under the hood. You should also check tensioner pulley at a time as it can also make a growling and squealing noise. 

Squealing Noise

3. Heavy Steering

Serpentine belts help provide power to power steering assist system. So, if the belt gets damaged, you’ll need significant effort to steer your vehicle. However, a bad steering rack, faulty power steering pump, or lack of steering fluid can also make it difficult to steer a vehicle. 

4. An Overheating Engine

If your engine overheats quickly, it can be result of a malfunction of water pump. This is because a bad serpentine belt may not provide power to water pump to keep the engine cool. 

An Overheating Engine

Risk of Driving With A Bad Serpentine Belt

A bad serpentine belt affects plenty of vital parts of engine including power steering, battery, alternator, and electronic devices. So you can experience the following risk of driving with a bad serpentine belt:

Consequences Of Driving With Bad Serpentine Belt

Acceleration Problems

A damaged serpentine belt can affect acceleration. When serpentine belt wears out or gets damaged, it loses tension and starts slipping along pulley system. It can create a screeching noise when accelerating. Power steering may also get insufficient power due to belt slipping and reducing car acceleration ability.

Loss of Power

A loose or cracked serpentine belt won’t let alternator charge battery to power the ignition system, air conditioning and power steering. So you’ll notice the battery isn’t a charging symbol on dashboard and experience loss of engine power while driving. If you continue driving, it can cause engine failure or car can go into limp mode. 

Engine Misfire

A worn-out serpentine belt can impact an engine’s timing and lead to a misfire. A faulty serpentine belt also causes a change in crankshaft speed and forces engine to misfire. Loose serpentine belts also cause cylinders to open and close earlier than usual and make noise and car engine vibration

Engine Misfire

Alternator Problems

If serpentine belt breaks or slips off, alternators will burn out and battery will deplete after running the car for a while. It’ll also cause a malfunction in the car’s ignition system, ECU, fuel system, and electricity-dependent component. 

Alternator Problems

How Much Does It Cost To Replace A Bad Serpentine Belt?

You can’t repair a cracked, broken or mended serpentine belt. So the only way to fix serpentine belt problem is to replace it. On average, serpentine belt replacement cost ranges between $109 and $134. While labor charges around $57 to $72, and parts cost between %52 and $62. However, the exact cost varies depending on your car’s make and model and the mechanic shop you choose.

You can also replace the serpentine belt at home garage particularly if you have some DIY skills. To do so, you’ll need to disconnect battery, pull the hood, and realize the cabin. Then you’ll need to relieve auto tensioner using a wrench, loose alternator cricket’s bolt, and pull off the belt. Finally, you can replace new serpentine belt, route it through pulleys and apply right pressure on auto tensioner to complete the task.


Can A Serpentine Belt Cause Transmission Problems?

A serpentine belt is connected with transmission. So a bad transmission won’t cause transmission problems or shifting issues. It’ll only hurt the power and essential accessories it drives.

What if Serpentine Belt Breaks While Driving?

If serpentine belt breaks, you’ll struggle to control steering. After a while, battery will die and water pump will stop working. Engine will become overheat and shut off in the end. So you’ll need to tow the vehicle to mechanic shop.

Can A Serpentine Belt Cause An Engine To Stall?

A severely broken or damaged serpentine belt can cause an engine stall. The reason is that the engine, will turn off the alternator and cause a loss of power and the engine will stop.

Final Words

Serpentine belt powers plenty of vital parts of engine. When it gets damaged, it’s obvious that the engine will get hurt from all around. So a bad serpentine can cause rough idle, loss of power, acceleration problems and can damage the engine completely. If you notice bad serpentine belt symptoms, replace it immediately to avoid causing severe issues.

My name is Henry Roberts and I am an experienced car mechanic with over 15 years of expertise in the automotive industry. I am currently running a Auto Repair Shop in Denver, Colorado. I have been servicing and repairing vehicles at my shop, where i have built a solid reputation for my skill and knowledge. I am passionate about sharing my automotive knowledge through blogging and my goal is to provide accurate and helpful information to car owners to keep their vehicles in perfect condition.

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