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What Causes a Crankshaft Seal to Leak

February 11, 2024 | Victor Lukasso

The main job of a Crankshaft Seal is to protect the oil in the engine from the air, but some factors can cause a crankshaft seal to leak.

A Crankshaft uses its rotational speed to propel the vehicle and power other electrical components. These components exert pressure on the crankshaft, leading to wear out if improper lubrication occurs.

Once lubricant’s lost, the heat rate (friction) will increase, causing the crankshaft seal to break off and leak oil into the crankcase.

Once your Crankshaft seal starts leaking, it’s often accompanied by a hissing sound from your engine, oil leaks, damaged crank gasket, and crankshaft wear out, which might be hard to diagnose.


In this article, I’ll show you the symptoms, what Causes a Crankshaft Seal to Leak, and how to prevent your Crankshaft seal from leaking.

Crankshaft Seal Leak – Symptoms

These are some of the symptoms accompanied by a crankshaft seal leak. Some of these symptoms might be associated with other car faults too.

  • Oil leaks around the engine
  • Hissing noise when accelerating
  • Smoke from the car hood
  • Low engine performance etc.
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What Causes a Crankshaft Seal to Leak?

One or a combination of the below factors can cause a crankshaft seal to leak.

1. Worn-out Gaskets

Too much exposure of the head Gaskets to heat can lead to an increase in wear and tear. Especially when the engine is deprived of smooth oil flow resulting in friction starting off the surface of the seal.

2. Expired or Damaged Crankshaft Seal

Crankshaft seals have a specified working duration. If you install an expired or weak seal on your engine, it’ll start breaking off quickly, leading to leaks.

It would be best to buy authentic Crankshaft seals for the best performance.

3. Impact from external objects

If dirt, grime, or sharp particles get in between the seal and crankcase, it’ll cause friction between both bodies, eventually leading to leakage over time.

4. A Cracked Metal Shell

The crankshaft seal has a metal shell that prevents air from getting into the oil.

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If there’s a break-off on any part of the metal shell, it’ll result in the air mixing with oil defying the primary function of the crankshaft seal.

5. Crankshaft Wear Out

If, for any reason, the crankshaft starts wearing out beyond repair, the crankshaft seal will begin losing its grip, and a leak will occur.

How do you Stop a Crankshaft Seal from leaking

You can deploy many DIY techniques to make your Crankshaft seal serve you longer and better.

Since the crankshaft functions smoothly if the appropriate amount of oil is introduced in the engine, here are some tips for you.

  1. Change engine oil at recommended intervals and amount
  2. Avoid driving your car at high speed, especially after a repair has been done to your vehicle.
  3. Install the original crankshaft seal on your vehicle.
  4. There’s no way to stop a crankshaft seal from leaking because it’ll spread over time, but you can employ some practice to make it serve you longer.
  5. Always top up your oil as recommended in your buyer manual, and avoid installing an inferior crankshaft seal on your vehicle, as it’ll get damaged in no time.
  6. Also, avoid driving at high speeds, mainly when a fix has just been carried out on your car since the loads might fall to your crankshaft leading to leaks.
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Crankshaft Seal Leaks – How to Repair

Since what Causes a Crankshaft Seal to Leak many, let’s look at some fixes you can implement for each.

  • Replaced worn-out or damaged crank
  • Cracked Metal Shell repair or replacement – depending on the severity of the damage
  • Inspect and get rid of dangerous matters around the seal.
  • Make use of a sealing solution.
  • Get a crankshaft replacement if necessary you can reach out to a mechanic close to you before doing this.

Most of these fixes are easy to implement at home, depending on your knowledge of vehicles.

However, If you don’t know the crankshaft seal and its location, you can take your car to a nearby mechanic for repairs.


What would happen if the crankshaft seal was leaking?

Some things that would happen if a crankshaft seal leaks are a hissing sound from your engine, oil leaks, damaged crank seal, and Increased Crankshaft wear out.

What causes oil to leak from the crankshaft?

A broken, damaged, or worn-out crankshaft seal is the leading cause of oil leaks from the crankshaft.

How many crankshaft seals are in a car?

Two crankshaft seals are situated in a car; they are placed at both ends of the crankshaft to prevent oil escape.

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Meet Victor Lukasso, the owner of V. Auto Basics. Through this blog, Victor Provides Insights on the latest tips, maintenance, repair, and techniques in the automotive world.