Noise When Decelerating – 3 Possible Causes & Solutions

Have you been noticing your car making a whining noise exactly when it’s slowing down? There might or might not be additional vibration to the car. 

Everything else seems to be fine except when you’re decelerating. The whole situation might come off as a mystery at this point.

So what’s the reason behind the noise when decelerating?

Noise when decelerating can be a cause of damaged parts. Such as the broken water pump or the transmission system. Also running on low fluid can be the reason. But in most cases, the culprit seems to be the pinion bearing. Other wheel bearings can cause similar noise as well. 

Wanna know how to deal with these issues? Then keep reading our post until the end. It may hold answers to the questions you were looking for.

Let’s begin!

Reasons Why a Car Makes Noise When Decelerating

A loud whining noise from the car when decelerating can happen for many reasons. Even if you are quite knowledgeable about cars this may seem like a mystery.

Source: allstate.com

That’s because it’s confusing to pinpoint the reason behind it. So let’s take a tour of our segment below. Hopefully, you’ll be able to identify it.

Reason-1: Faulty Water Pump

You may wonder what the whining noise has to do with the water pump. But it can be the reason why the car makes loud noise when decelerating.

The car water pump is responsible for supplying coolant for engine. Since the engine runs at a high temperature, it tends to overheat. The temperature thus has to be maintained in other ways.

A water pump is used for this purpose. To ensure the engine doesn’t overheat and damage itself it flows coolant. It goes through the cooling system and proceeds to cool down the overheated engine.

So what happens if it goes bad? You can imagine how the temperature maintenance is about to get messed up. One of the signs is that a faulty water pump makes a whining noise.

It could imitate a squealing sound if the bearing is faulty as well. Additionally, you may see the coolant leaking from the pump. 

Solution

Luckily, fixing a broken water pump on a car is quite simple. You can do it yourself as long as you have a wrench in your hand. But the downside is that it’s a lengthy process.

So if you need a quick fix to this, first check the fan belt. Make sure that it’s not damaged. Also, check the radiator coolant. If it’s empty then it means your car engine won’t get any coolant.

Lastly, check the impeller of water pump. If it’s not spinning then give some water to the radiator. It would hold off your car until you take it to a nearby shop.

If you see that your water pump is extremely damaged, then you have no other option than to replace it. 

Here are some good quality engine water pumps that last a long time: 

Gates 45006 Water PumpGet Now!
ACDelco Professional 252-845 Engine Water PumpGet Now!

Now that you have your replacement water pump, you can simply change the damaged water pump. By following this video from ChrisFix you can easily replace the water pump of your car at home-

Reason-2: Damaged Transmission Gear

Similar to water pumps, transmission gears can cause noise when decelerating. You may also experience vibration along with the noise.

transmission makes humming noise rather than a whining sound. Transmission system gears can get worn out due to long use. So the damaged gears can make loud noises.

Transmission lines running on low fluid can also be the reason. Similar to the water pump, the transmission cooler line carries fluid to the car engine. 

Sometimes due to a broken transmission cooler line while driving the fluid may leak. The problem is quite similar to the water pump issue.

Solution

If the transmission system has gone bad then you may see some additional changes. You may face some shifting delay, shaking, vibration, or jumping sensation while in the drive.

If the fluid leaks then there will be a burnt smell as well. So check the fluid amount in your transmission system. If it’s running low you’ve to refill it.

Always try to get good-quality transmission fluids. There are some transmission fluids available on the market that dries up quickly. Avoid using them. 

Instead of using those low-quality transmission fluids, opt for higher-quality ones like the following: 

ACDelco GM Original Equipment 10-9244 Dexron VI Full Synthetic Automatic Transmission FluidGet Now!
Valvoline Multi-Vehicle (ATF) Full Synthetic Automatic Transmission FluidGet Now!
Castrol 03518 Transmax ATF Green High Mileage Transmission FluidGet Now!

If the problem remains with the old and damaged gears then get them replaced. The best would be to run a transmission system check on your car by professionals.

If fixing it doesn’t solve the problem then move on to the next part.

Reason-3: Wheel Bearing

Faulty wheel bearings are the first thing to suspect when noise comes while decelerating. In most cases, it’s the pinion bearing that causes the issue.

Source: carthrottle.com

The noise comes from the loss of pinion bearing preload. It’s different from the grinding noise while coasting in gear.  

When the bearing gets pressed on, the crush sleeve sits in between them. Thus creating tension between the inner and outer bearing. 

As a result, the preload can get messed up. So the bearings start to wobble around the pinion shaft while decelerating and making noise.

Other wheel bearings can be the cause too. They’re different from engine bearings. These bearings don’t have any source of lubrication.

So they must be kept safe from water and dust to avoid corrosion. However, dirt and debris find their way inside it making them worn out.

These wheel bearings provide support to the entire weight while driving. So the damages accelerate once they start to wear out.

Solution

If it’s the pinion bearing that creates noise you’ve to take it down. Reevaluate the whole thing and set the preload again. You’d also have to make sure that it’s set within the spec.

As for the other wheel bearings, you can apply grease and tighten them up. If the parts are too damaged they may require a replacement. 

You can change these parts by using a wheel-bearing tool kit. If you don’t have one at your hand at the moment, we suggest these options-

Astro Pneumatic Tool 78825 25-Piece Master Front Wheel Drive Bearing Puller Removal & Installer Adapter KitGet Now!
Orion Motor Tech 23-Piece FWD Front Wheel Drive Bearing Adapters Press Kit Puller SetGet Now!

However, if DIY isn’t an option, take your car to a mechanic shop. There we’ll get a better diagnosis of the issue.

These are the most plausible reasons for this problem. However, there can always be other variables depending on your car model and condition.

Source: automotivesupercenter.com

So, better would be getting a check-up on your car in a nearby shop. But at least now you have a clue that something has gone wrong with your car.

FAQs

A little more information might come to your aid. So we prepared this section for you-

What causes the howl or rumbling noise while accelerating? 

The pinion bearings tend to make a rumbling noise when it gets old and damaged. The sound may resemble a howl with a whir. It’s either the damaged pinion bearing or the worn-out gear set.

Can I continue to drive a car with a bad wheel bearing?

Driving a car with bad wheel bearing isn’t safe. It’s dangerous even if it’s a single bearing that has gotten worn out. Because these wheels support the total weight of the car while on the drive. A worn-out bearing can cause a lot of stress to the CV joint. Also on the hub and transmission system.

How much does it cost to replace wheel bearings?

Replacing a wheel bearing can cost you $350 on average. The range will vary depending on the model and the labour work. If it’s from luxury brands then it would cost more. Also, the range for replacing one hub assembly from the front wheel varies extensively.

Conclusion 

That’s all from us regarding noise when decelerating. Have you figured out which one is the culprit yet? 

Whichever it is, if you’re in confusion don’t hesitate to reach out to the professionals. After all these tricky issues are best to be handled by the pros.

That’s it for today. See you soon!

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