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Home / Symptoms / Car Battery Leaking

Four common causes for a vehicle leaking red fluid and their related parts.

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Is Your Car's Battery Leaking?

The battery is leaking because it has been banging on the hold-down rack. In this case, the rack or the battery's support might be loose, causing wobbly movements. However, the leak can also come from the terminals getting excess vibrations. Alternatively, if chemical reactions cause internal shorting, the battery can swell and crack.

Don't let the problem build up. It's always a good idea to seek the advice of an experienced technician to help you diagnose and fix the issue. By addressing the car battery leak early on, you can avoid costly repairs, keep your vehicle in top shape, and have peace of mind knowing you're safe on the road.

Watch out: Don't ignore a leaking car battery! This is a clear warning that your vehicle's roadworthiness is compromised, which could lead to unsafe conditions. It's time to take control and understand what's causing the problem and what you can do about it.

The most common causes for a vehicle battery leaking

The most common causes for the car battery leaking:

Defective battery hold-down: The battery hold-down is where the battery case is attached to. The hold-down supports the battery, and the battery can be removed by releasing the screws holding it in place. However, the battery hold-down can get bent, loose, or dislodged, making the battery wobbly, and resulting in friction and impact, leading to leaks.
Battery sensor failure: The battery sensor reads information like temperature, voltage, and current. The battery sensor is connected close to the battery's fluid reservoirs, and it can lead to leaks if it's worn, acting as a passage for the fluids.
Battery internally shorted: A battery short-circuit can lead to chemical reactions inside the case that might result in gases and corrosion. In this case, the battery case might get bloated and cracked, resulting in leaks.
Alternator overcharging: The alternator generates voltage, which is sent to the battery. However, if the alternator produces too much voltage, it might overheat the battery, leading to internal short-circuit and electrical reactions, which can result in case bloating and leaks.
Cracked battery case: The battery case is made of resilient plastic. However, if the battery overheats, it'll lead to damage to the case, which can't resist high temperatures. Consequently, the case might crack. Additionally, the case can also crack due to age, fender benders, etc.
Battery post seal leak: The battery post seal is a rubber seal closing up around the battery's terminals, preventing battery acids and fumes from leaking in the terminals. However, these seals can get faulty, losing sealing and leading to corrosion.

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Frequently Asked Questions

Is the red battery warning light active on the car dashboard?

The alternator is like the battery charger in your car. It ensures the battery has enough power to keep everything running smoothly while driving. The alternator has a "little helper" called the voltage regulator, which ensures that power stays at the right level and doesn't get too high or too low. If the voltage regulator stops working correctly, it can cause the alternator to give the battery unmeasured amounts of power. This can trigger the battery light on your dashboard to turn on, signaling something is wrong.
Does the car's battery terminals show clear signs of corrosion?

Most car batteries are sealed tightly to keep acid inside. But when other parts start to wear out, like the suspension or motor mounts, the battery jostles around; this causes tiny gaps to form around the battery cables. These gaps allow some of the acid gas to escape, making the ends of the battery cables corroded and nasty.
Does the battery appear to be wet?

Inside a car battery, some plates or cells hold acid and create energy for the car. A plastic housing separates the acid to keep everything safe and prevent short circuits. But if the battery gets damaged, like in an accident, it can cause the plastic housing to crack, and the acid can spill out. So even if the battery is securely tight, the housing can still crack and cause an internal acid leak. As a result, the battery might look wet or sweaty on the outside.
Is the battery looking bulged?

If your car battery is sealed, but the suspension or motor mounts are wearing out and making the battery bang around, there might be problems. The plates inside the battery can get damaged and short-circuit. This results in gases building up inside the battery, bulging it like a balloon. This can be dangerous, so consider assistance if your battery is swelling.
Can the battery freely slide around the battery tray?

The "battery hold down" is like a large metal belt that holds the battery on its tray. However, it wears quickly over time since it's so close to the battery and the acid inside. When this happens, the hold-down can break, making the battery loosely slide around the tray. This can be dangerous as the battery might bump into engine components or cause an electrical short by bumping the wrong spots.
Is the "check engine" light on the dashboard?

Your car's computer is smart enough to monitor the battery temperature. It uses a particular sensor that tells how hot or cold the battery is. This helps the computer ensure the battery charges at just the right speed. However, if the sensor goes on the fritz and sends the wrong information, it can cause trouble. For example, if the sensor always says the battery is too hot, the computer might charge it too much. And if it always says the battery is too cold, it might not charge it up enough. When this happens, the "check engine" light will warn that something's wrong.

Typical fixes to address the cause(s)

These are typical processes and repair services that fix a check engine light issue

The most common cause: Battery hold-down failure

The most common reason for a battery leak is because the battery hold-down is not supporting the battery enough, causing it to bang around its compartment. The battery hold-down is a tray where the battery is secured with screws. However, this tray can get loose and lose stability, resulting in a wobbly battery that can bang around the compartment. Consequently, the battery will take hits as you drive, damaging the case, terminals, and connectors, leading to leaks.

Symptoms it causes: Apart from the battery leak you might notice electrical issues, banging sounds, a battery warning light on the dashboard, difficulty starting the vehicle, etc.
High risk of priority: An unsafe battery hold-down puts the battery at risk. The battery is the vehicle's heart, ensuring it can start and drive. However, if the battery is at risk of damage, the vehicle is at risk of stalling and breaking down unexpectedly.

How exactly does the battery hold-down fail?

A battery hold-down is made to last for roughly decades. However, they're prone to wear out sooner depending on driving conditions. If the vehicle is old, the battery hold-down might be rusty and unreliable. Additionally, if a vehicle gets into a fender bender, the battery hold-down might get slightly dislocated, leading to future problems. Driving conditions like bumpy terrain and rough roads can also result in excess vibrations in the battery compartment that can damage the hold-down.

Go safe: Ask for a mechanic to inspect your vehicle’s battery and charging system to investigate if the battery hold-down is failing due to surrounding components and if there’s further damage to check out. Many shops do transparent vehicle inspections and lay out your options after investigating your vehicle’s conditions.

What’s a vehicle inspection? It’s “detective work” on your vehicle, checking its systems to see if anything prevents the car from working as expected. In this case, mechanics examine different parts of your vehicle to track if anything is causing the battery hold-down to fail. They’ll also check the condition of components during their inspection, noting which are causing the problem and which got affected by it, recommending to replace them in order of priority.

Transparency example in a faulty camshaft service

A charging system inspection is the most transparent process to understand why your vehicle’s battery is faulty. This is because many components surrounding the battery and charging system components like the alternator and serpentine belt can have a say in the issue, indicating the real culprits that caused it all.

Let’s read an example of how this kind of inspection helps to service a weak battery, fixing an ignition problem.

When the customer dropped off their vehicle, they informed us that the battery hold-down bolt was broken and the battery was sliding around in the battery tray. The customer had tried to remove the bolt but couldn't, as it was seized in the metal part in front of the radiator, and nothing was sticking out to remove the broken-off bolt.

During the test drive, the technician didn't notice anything about the customer's concern. However, during the vehicle health inspection, the technician noticed that the front bolt into the radiator core support was broken. Consequently, the battery could slide back and forth.

The customer authorized additional tests to extract the bolt from the radiator core support. Then, the technician used a drill bit to drill out the center of the bolt and used an extractor to remove the bolt from the radiator core support.

Next, the technician secured the battery hold down with a new bolt. Additionally, the technician cleaned any remaining acid on the battery holder and sealed it with a battery sealing spray.

Defective battery hold-down

In this case, the mechanic put the “Immediate Action” tag on the battery and the battery hold-down.

Similar Symptoms

Below are just a few examples of typical Symptoms and Fixes your car might be experiencing

Four common causes for a vehicle Leaking Oil and their related parts.

Is Your Car's Battery Leaking?

The most common causes for a vehicle battery leaking

Find Professional Help

Frequently Asked Questions

Is the red battery warning light active on the car dashboard?

Does the car's battery terminals show clear signs of corrosion?

Does the battery appear to be wet?

Is the battery looking bulged?

Can the battery freely slide around the battery tray?

Is the "check engine" light on the dashboard?

Typical fixes to address the cause(s)

The most common cause: Battery hold-down failure

How exactly does the battery hold-down fail?

Transparency example in a faulty camshaft service

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