What Causes a Crankshaft Seal to Leak?

Naomi O'Colman

What Causes a Crankshaft Seal to Leak

What Causes a Crankshaft Seal to Leak

What causes a crankshaft seal to leak? Crankshaft seals can be affected by a number of conditions.

One of the most common reasons that a crankshaft seal will leak is exposure to high heat in a vehicle engine bay. Over time, exposure to heat will cause the material in the seal to deteriorate and break down, causing it to leak.

This simple component won’t catch your attention until the problem comes. Let’s look at what causes a crankshaft seal to leak?

What Is a Crankshaft Seal?

A crankshaft seal is a small, yet critical component that is designed to prevent oil from being pushed out from between the crankshaft and the cylinder block. This oil creates a barrier between the two parts of the engine. This keeps moisture and dirt from entering.

The seal itself has a very small, unobtrusive design that is made out of rubber or other materials that seal against metal parts so it fits in tight spaces. It is compressed by the bolts on either side of it. However, this pressure will cause it to break down after time, causing a leak.

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What Causes a Crankshaft Seal to Leak?

#1 Wear & Tear

A common cause of a leak from this component is exposure to high heat that can break the seal down over time. When a person drives a vehicle that has an open engine, high temperatures can build up in the engine bay and create an environment where these seals will deteriorate sooner.

A crankshaft seal is usually in good condition for about 100k miles. After that, it will deteriorate and then leak. High temperatures in a car will cause this to happen faster.

#2 Corrosion

Another common reason for a leak from this component is the corrosion of the seal itself. When water gets under the seal, it can cause the metal on which the seal is compressed to corrode, causing it to break down faster than normal. This is why many people will place an oily rag over their vehicle’s engine bay when driving during winter months to prevent rust from building up on this component.

#3 Crankshaft

Both wear and deterioration of the seal from corrosion is 100% due to the crankshaft. The crankshaft is a metal part that must be in great shape for a seal to survive. If there is any problem with its surface, it will push out moisture into the seal and cause corrosion. This can then cause a leak from the seal.

#4 Bent Or Broken Hinge Pin

A bent or broken hinge pin is another cause of a leak from this component. The pin is usually made of metal and fits into a hole on the crankshaft and cylinder block. If there is any damage to this part, it can bend, which will cause the seal to fail quickly.

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Symptoms of A Bad Crankshaft Seal

# Rhythmic Hissing Sound

A leak from this component will usually cause a rhythmic hissing sound when the engine is running. No other symptoms are usually noticed unless it is bad enough to make the vehicle run poorly.

# Oil Leaks From Front Engine

Another sign that you can look for is oil leak out of the engine while it is not running. You can also check your engine for bad or damaged seals by using a magnet or magnet test strip, which is available at most automotive parts stores.

A common problem with these components is the “leaks” that are actually cracks in the seal itself. This will cause oil to leak out when you turn the car on. That is why they are sometimes called squirts.

How to Fix a Crankshaft Seal

#1 Reinstall the Old Seal

If you determine that the crankshaft seal is leaking, simply remove it and then take it into an auto parts store to get a replacement. Install the new one exactly where the old one was and then install all of your old seals back on.

#2 Machine the Crankshaft

Vacuum testing is done to check if there is anything on the crankshaft that could be causing the seal to leak. This method is very expensive and time-consuming, so most auto repair shops will use something called “crankshaft grinding” instead. This involves using a special grinder that screws into the crankshaft. The crankshaft is then pressed in using this machine to grind away any parts of it that are creating stress on the seal.

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A damaged or bad seal is one of the most common causes of a leak. It will also cause an engine to run rough or shake when it is on idle. A faulty seal can be fixed cheaply and quickly. It may even make your vehicle more effective at stopping and improving gas mileage and in some cases, increase power in the engine.