6 Reasons Why Engine Oil Cap Won’t Come Off

Reasons why engine oil cap won't come off.

Have you ever found the engine cap difficult to get off? If so, you’re not alone.

In this post, you will learn the potential causes behind why your engine oil cap might be stuck and tips on removing it safely.

Here’s what we’ll cover:

How To Remove the Engine Oil Cap?

Start with locating the oil cap on your engine block, near the top of the block, with a bright yellow or orange coloration.

Make sure not to mistake it for the radiator cap! 

Once you’ve identified this part, use gloves or a rag to prevent any dirt or debris from entering the opening when you unscrew it.

Next, twist counterclockwise until it comes loose — be gentle but firm here so that you don’t strip any threads on either side of the opening. 

And you are done!

If this doesn’t go as planned, read on to find possible reasons and solutions.

Reasons Why Engine Oil Cap Won’t Come Off

Here are six reasons why your engine oil cap might not be coming off.

1. Hot Engine

A hot engine can be one reason your oil cap does not come off. When an engine gets too hot, the oil cap expands due to heat expansion, making removing it difficult or impossible.

It is visible when a car has been running for an extended period and has not cooled down enough for the heat to dissipate.

You can avoid this problem by ensuring your vehicle is well-ventilated before changing your oil or checking its level.

2. Overtightening

The issue occurs when a person puts too much force into turning the cap, causing it to fasten itself onto the engine block. Over time, this can cause corrosion and buildup around the threads, making it impossible to twist them off without extra force.

3. Gunk Buildup

Gunk buildup is one of the primary causes of the engine oil fill caps not coming off. This can be caused by several things, including dirt and debris getting into the oil or using thick oil that drains slowly.

If left unchecked, gunk buildup can be difficult to remove from your vehicle’s engine and cause further complications such as clogged filters, decreased fuel efficiency, and increased emissions.

4. Wear and Tear

If the threads of the oil cap are damaged due to wear and tear, it might get difficult to unfasten the engine oil cap.

5. Long Oil Change Intervals

Putting off oil changes often means the engine oil filler cap will stay on. It causes the seal around the cap dry out and become brittle, making it impossible to remove without causing damage.

6. Damaged or Broken Seal

If you have been trying to change the engine oil in your car but are having difficulty removing the oil cap, it may be due to a damaged or broken seal. A seal on an engine oil cap is typically made of rubber and can become brittle over time while losing its better grip.

This can cause it to crack or break off from the base of the cap, creating an airtight seal and making it difficult to remove.

Hacks to Open a Stuck Oil Cap

Now that you know why an engine oil cap might be stuck, let’s explore the possible solutions.

1. Apply Engine Degreaser

One of the hacks to open a stuck oil cap is using an engine degreaser to loosen up any dirt and grime around it. Engine degreaser is an easy-to-use spray that breaks down stubborn residues on your vehicle’s surface, including around your oil cap.

Before spraying it directly onto the oil cap, cover nearby parts with plastic or cloth to protect against the strong formula in the engine degreaser.

Engine oil cap won't come off — Apply engine degreaser.
Image source: Northeast Auto Service

2. Apply Ice

Oil caps can be tricky to open and, worse, when stuck. Fortunately, there are a few hacks that you can use to help get the oil cap off. One of these proven tricks is applying ice. Applying ice is an effective way to loosen stuck oil caps.

The process is simple. Wrap a small bag of ice cubes in a cloth or towel before pressing it against the oil cap for several minutes. 

The cold from the ice helps contract the metal around the cap, making removal easy without damaging anything else in your car’s engine bay.

3. Wait for the Engine To Cool Down

Wait for the engine to cool a bit before opening a tight oil cap. It’s worth trying before you resort to other methods, such as penetrating oil or a wrench.

This method benefits from metals contraction when they cool down. You can remove the oil cap without damaging it by allowing your engine to cool for an hour or two.

4. Open Forcefully

Another hack is to use a screwdriver as leverage. Using two screwdrivers of different sizes, one should insert the smaller one into the indentation of the lid.

Use force to open engine oil cap.
Image source: NAPA

Then use another tool such as pliers, strap wrenches, or channel locks to hold steady while pressing down on the large pair of a screwdriver. This pushes up against the lid and eventually loosens it enough that you will have access to your oil cap.

Final Thoughts: 6 Reasons Why Engine Oil Cap Won’t Come Off

If you find yourself in a stuck engine oil fill cap, the steps above can help you safely and effectively remove it. Remember to be cautious when using tools or lubricants, as some materials may not be safe for your vehicle.

Consult a professional technician if you still need help after trying these steps.

For more engine-oil-related queries, explore our blog.

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