Serpentine belts depend upon idler pulleys that glide freely without interference. Through normal wear and tear, idler pulleys can deteriorate, and noise will be the first indicator that idler pulley problems are approaching.
Deal with small noise now before you end up in a costly repair situation. We will cover possible causes of idler pulley noise, how to isolate the noise source, and what the replacement costs will be.
What is an Idler Pulley?
An idler pulley is simply a small wheel that guides a drive belt in your vehicle’s engine. It doesn’t drive anything specifically; it only changes the direction of the drive belt.
They are simple little components, but they are very important in making sure that your serpentine belt operates smoothly.
Common Causes of Idler Pulley Noise
When you hear a noise coming from the idler pulley, it is due to one of three causes. Pulley wear, slippage, or complete pulley failure. Below is a description of each of these causes, in the order you can expect them to occur.
It is important that you pay attention to the noise. They can go from bad to worse quite rapidly. The noise that you hear from the first cause should be reason enough to have your vehicle examined by a mechanic.
If you do not act quickly, the sounds will worsen and lead to more serious issues that will cost you a lot of money to fix.
#1. Pulley Age/Wear.
The idler pulley is always rotating with the drive belt. If the wear is significant enough, this will affect the surface of the pulley. After years of revolving, the pulley will develop scuffs/marks on the surface.
This is when you will start to hear noises. Although be mindful that the noises will be only minor to begin with.
#2. Bearing Problems.
If you hear a chattering/chirping or squealing noise in your vehicle, it is probably a bearing problem with the idler pulley. All bearings wear out with age. Over time, the bearing will loosen, seize, and become overheated.
Each time you start your engine, you may end up with an unwelcome noise.
#3. Pulley Slippage.
Idler pulley slippage will often follow when an idler pulley has worn out enough to allow for this to occur, causing the idler pulley to bind and rub against the engine belt.
Therefore, you will have squealing noises coming from the engine area that only get worse until you replace the idler pulley.
Not only that, but it could also add more belts and other components to the engine.
#4. Pulley Damage.
In extreme case scenarios of neglecting the first two causes of idler pulley noise, the idler pulley would eventually become damaged and ultimately break altogether.
The pulley would form cracks and start to break apart slowly, causing a chain reaction where the serpentine belt would tear or break altogether.
If this occurs, you will have several engine issues, like stalling and overheating.
On top of that, the screaming noise would become louder and annoying to everyone inside and outside of the vehicle.
#5. Serpentine Belt Problems.
The engine relies heavily on the serpentine belt to drive essential components in the vehicle, like the alternator, water pump, and power steering pump.
However, a serpentine belt that is worn out or damaged could slip, causing screaming noises. This may include an idler pulley providing the proper tension for the serpentine belt.
To prevent any complications from occurring, check the serpentine belts for signs of wear regularly to check for cracks or uneven wear on the belt.
If things do not look good with the belt, you should take your vehicle to a local independent repair shop or dealer service department mechanic to replace the serpentine belt.
Idler Pulley Replacement Cost
To replace the tensioner pulley, expect to pay between $80 to $200.
The part should cost between $40-$90, and labor should typically cost between $40-$110; these estimates do not include taxes or fees from the auto shop.
So, all in all, this is an inexpensive replacement since the drive belts rely on the idler pulley, so don’t wait too long to replace this part once it wears out.
Is it safe to drive with a bad idler pulley?
Although it’s not a safety concern to drive with a bad idler pulley, you really shouldn’t as you can potentially do immediate damage.
Identifying the problem with the idler pulley is usually based on a consistent squeaking noise produced by the motor that increases with higher RPMs.
Indicators like this are not just annoying, but the wear and tear caused by the pulley surface, in addition to a seized or loose bearing, will put a lot of wear on the drive belt alongside other components.
In these cases, a relatively cheap issue can escalate into something significantly expensive.
Idler Pulley Noise Diagnosis
Visual Inspection
Before we get too technical, it is important for us to always start with a visual inspection and go from there. Open up that hood and take a close look at the engine bay.
Look closely at the engine pulleys, especially the idler pulley, to make sure that it is nice and tight and that it isn’t showing any signs of wear or damage.
You should be on the lookout for pulley grooves that may be worn, a torn belt, or other signs of slippage in the belt. You should also look for any signs of coolant or antifreeze exposure to the pulleys and belts, as these fluids can cause damage and lead to strange sounds.
Noise Identification
Now let’s concentrate on identifying the particular noise your idler pulley might be making.
A common sound symptom that indicates a bad idler pulley is a chirping or chattering sound from the engine bay.
Oddly enough, if you are experiencing this noise, it can often be more noticeable in cooler weather as the pulley bearing might be frozen or stiff, causing the pulley to produce a chirping or chattering noise.
To pinpoint where the noise is coming from, start the engine and monitor it carefully. It is important to pay attention to any changes in the noise as you vary the engine speed.
If it sounds louder when the engine speed increases, or louder when you are using the air conditioning, it could be the idler pulley.
Check for Play
Finally, check the idler pulley for play. Wiggle the pulley back and forth and see if you feel any looseness. A worn or damaged pulley may produce unwanted play, which could be the underlying cause of that irritating chirp in your engine bay.
Preventative Steps
Proper Tension
One of the easiest ways to avoid idler pulley noise is to make sure your vehicle has proper tension with your belt system. Ultimately, noise from your serpentine belt can be linked to a bad tensioner or bad bearings on the pulley.
Check the belt system often for looseness and pull it tight when you do. The more holding the tensioner provides, means more torque can be provided, without belt squeals or stalling.
On the other hand, too much tension can create excessive wear on the bearing due to friction and damage to the pulley. Adhere to the manufacturer’s recommendations closely and if in doubt, consult a trained mechanic.
Regular Maintenance
After proper tension, let’s cover the topic of regular maintenance of your vehicle, if you wish to avoid any idler pulley noise (and other issues, too).
For now, we will check on the idler pulley mounting bracket, in this case, is not bent or damaged. A bent or damaged mounting bracket may lead to untold issues within a belt system, as well as unexpected noises.
Here are just a few other ideas for maintenance:
- Inspect the idler pulley for scuff marks, wear marks, or corrosion. A corroded surface can create belt squeal noise, coupled with a very high possibility of decreasing a vehicle’s performance.
- Go ahead and listen; chattering squeals or chirps can be indicative of issues with either the idler pulley bearings or the belt system.
- Inspect factory belts frequently to look for cracks, frays, or degradation. Replace as necessary.
- If appropriate, lubricate the bearings in the idler pulley. Lubrication will help to reduce friction, increasing a component’s life cycle. Be careful of over-lubrication, as this can unwittingly create slippage and cause squealing.