There’s an old saying in the motor trade: “It’s only a small oil leak.”

Unfortunately, sometimes it isn’t.

A 2009 Mini Cooper recently came into the Autosavvy Mechanical workshop with a substantial engine oil leak. At first glance, it might have appeared to be a fairly routine repair.

But as we investigated the problem, it became a good example of why engine oil leaks are worth dealing with before they have a chance to cause further damage.

It wasn’t just a little bit of oil

Our inspection quickly found that the rocker cover gasket and spark-plug seals were leaking heavily.

There was actually so much oil present that the spark-plug tubes were completely filled with oil.

The ignition coils, surrounding wiring, air box and intake components had to be removed so the rocker cover could be taken off. The mating surfaces were cleaned and new rocker cover and spark-plug seals installed.

The oil in the spark-plug tubes was also removed before everything was reassembled.

At that point, you might think the problem was solved.

It wasn’t quite that simple.

One leak fixed — then we found another

After replacing the rocker cover gasket and spark-plug seals, the engine was thoroughly cleaned and degreased so we could see whether there were any other sources of oil leakage.

This is an important part of diagnosing an oil leak. When an engine has been leaking for some time, oil can spread over a large area, making it difficult to identify exactly where it is coming from.

Once the engine was clean, we were able to inspect it again and discovered that there was still fresh oil appearing behind the harmonic balancer.

Further investigation identified the source: a steel cover-plate Welsh plug located behind the harmonic balancer was leaking oil.

Unfortunately, it had already caused another problem.

The oil leak damaged the harmonic balancer

The harmonic balancer contains a rubber section designed to isolate vibration between the inner and outer portions of the balancer.

Because the Welsh plug had been leaking oil directly in this area, the rubber in the harmonic balancer had become oil contaminated and subsequently failed.

That meant the harmonic balancer itself now needed to be replaced.

The drive belt had also become heavily contaminated with engine oil and required replacement.

So what started as an engine oil leak had actually developed into multiple repairs:

• The rocker cover gasket was leaking heavily.
• The spark-plug seals were leaking and the plug tubes were filled with oil.
• A Welsh plug behind the harmonic balancer was also leaking.
• The leaking oil contaminated the drive belt.
• The oil damaged the rubber component of the harmonic balancer.
• The harmonic balancer therefore required replacement.
• The drive belt also required replacement.

Oil can travel a long way

An engine isn’t a stationary environment.

There are pulleys turning, belts moving and components vibrating. Oil escaping from one area can spread across the engine and underneath the vehicle.

It can contaminate:

• Drive belts
• Pulleys and harmonic balancers
• Electrical components and wiring
• Ignition components
• Rubber components
• Engine mounts and surrounding components

Older cars need preventative maintenance

The 2009 Mini Cooper is now an older vehicle, and as cars age, gaskets, seals and other components naturally deteriorate.

That doesn’t mean every older Mini is destined to have problems.

It does mean that owners should pay attention to small changes.

A few drops of oil on the driveway.

Oil around the engine.

A burning-oil smell.

Smoke coming from the engine bay.

Having to regularly top up the engine oil.

These can all be signs that something needs investigating.

Fixing the problem early can save money

An oil leak that is caught early may require nothing more than replacing a gasket or seal.

Leave it long enough, however, and the leaking oil can contaminate other components and create additional repair costs.

That’s exactly what we saw with this Mini.

The lesson is simple: if your car is leaking oil, don’t wait for the leak to become a bigger problem.

If you own an older vehicle and have noticed an oil leak, oil spots on the driveway or unexplained oil consumption, have it checked before a relatively straightforward repair turns into something more expensive.