It’s hard not to notice when your BMW is suffering from an oil leak. In addition to the tell-tale stains on your garage floor, it’s impossible to miss signs like:

  • Smoke
  • Overheating
  • Burning smells

And of course, it’s impossible to miss the ‘oil level low’ warning on the dashboard!

As we all know, oil is the lifeblood of your engine. It reduces corrosion, helps cool the engine and reduces wear-and-tear by reducing friction and keeping your engine well-lubricated.

There are many potential causes of a BMW oil leak – some of which our BMW specialists in Melbourne have written about before.

Today however, we’ll be focusing on one in particular: your PCV system.

Introducing: your PCV system

Even highly-engineered vehicles with tight tolerances aren’t immune to partially-burned fuel-air mixture slipping through the piston rings and into the crankcase. It’s unavoidable, and part of the design of low friction engines.

This partially-burned mixture is called blow by – over time, it builds up in your crankcase, adding pressure until your engine’s seals start to fail.

And that’s what the PCV (positive crankcase ventilation) system is meant to prevent.

The intake manifold operates at a different pressure to the outside atmosphere. This creates a natural vacuum when the PCV valve is open – the resulting intake vacuum draws blow by out of the crankcase, lowering the pressure.

By reducing pressure, your PCV system protects your BMW from a range of engine issues, prolonging your engine’s life and saving you a trip to a BMW specialist.

Of course, pressure isn’t the only function your PCV system performs – once removed, these vapours are mixed into the fuel-air mixture in the combustion chamber, where it’s fully burned, maximising efficiency and reducing emissions.

Don’t worry, the system is designed so that it only enters the combustion chamber while your car is idling – no need to worry about these vapours impacting your car’s performance!

The PCV valve: the most important part of the whole system

Most PCV systems use simple spring-loaded PCV valves, usually made of plastic. It isn’t uncommon for these parts to degrade and wear out over time owing to the heat and pressures BMW engines tend to generate.

Sometimes, it isn’t a break – in others, the valve can get stuck or jammed by a buildup of fuel deposits.

The PCV system in your BMW is made up of many different moving parts – the most important being the PCV valve. It wouldn’t be much of an exaggeration to say that the entire crankcase ventilation system hinges on this one valve.

Either of these issues can result in your PCV valve locking open or shut, which can lead to PCV system failure, which in turn can cause significant engine problems such as lean fuel-air mixture or pressure build-up respectively.

Of course, you aren’t here to learn about PCV valve failures – no, you want to know how this tine part failing can lead to an oil leak in your BMW.

BMW oil leak

Could your BMW oil leak be the result of a PCV system failure?

Your PCV systems’ primary job is to reduce pressure in the crankcase. If the PCV valve breaks and fails to open or is jammed shut, this creates a sealed system – nothing gets out of your crankcase, leaving you with a pressure build-up.

And that overpressure is directly linked to oil leaks.

The crankshaft seals as well as other engine seals and gaskets are tight enough to stop oil from leaking out under normal conditions – however, higher levels of pressure change the equation. Essentially, it pushes oil out past these seals and gaskets, leading to a BMW oil leak.

Additionally, it isn’t unheard of blow by (and the associated pressure build-up) to damage the gaskets and seals in the crankcase. It may not happen today, over time, the pressure can cause these seals to crack or break entirely. The result? Even worse oil leaks.

And it isn’t just oil leaks either – PCV valve failure also tends to be accompanied by other  oil-related issues such as excess oil consumption and engine oil degradation.

We don’t have to tell you that this can seriously affect your BMW’s engine!

Our BMW mechanics in Melbourne can fix BMW PCV valve failures

Despite its importance, very few car manufacturers – BMW included – list PCV valves as a maintenance item in their service guides.

And since PCV valve replacement isn’t listed in the service schedule, they often go years without replacement by either generalist or dealership mechanics!

Not only that, but because they aren’t listed in the service schedule, there isn’t a set time or distance interval where PCV valve replacement is mandatory.

Finally, PCV system problems are also often misdiagnosed since the symptoms look an awful lot like a vacuum leak.

This may not sound like a major issue, but hear us out: a lot of generalist and dealership mechanics rely on the service schedule to service your BMW. If it isn’t in the schedule, it may as well not exist to them!

As specialists, our BMW mechanics in Melbourne don’t blindly follow the service guide, or simply follow what your CBS system says – instead, our BMW specialists focus on giving your vehicle the service it needs.

Using powerful diagnostic tools and our wealth of experience, we identify issues that might be lingering in your vehicle. And that includes frequently overlooked problems such as PCV valve failure.

Is your BMW suffering from an oil leak? You can trust us to get to the bottom of it, whether it’s something obvious or something that’s easily overlooked like issues with your BMW PCV valve.

The drive towards better service starts here

Choose Ammstar’s BMW mechanics in Melbourne

Has your BMW run into an oil leak? You could go to a dealership to get it checked out – however, you’ll also have to pay a fortune for it.

While an independent mechanic will bring your BMW service cost down, there’s no guarantee they’ll be able to provide the same level of service you expect.

Luckily, our BMW mechanics in Melbourne offer the best of both worlds.

Operating independently from the dealership network, we’re able to be much more flexible with our service:

  • We aren’t tied down by the service guide, allowing us to adjust your BMW service as needed
  • We aren’t locked into restrictive parts contracts, giving us the freedom to seek out more affordable suppliers and parts
  • We use more efficient and streamlined processes, honed over 20 years

And it isn’t just vehicles from the Bavarian carmaker, either – our BMW mechanics in Melbourne can also fix problems from Audi, Mercedes-Benz and Volkswagen as well.

The drive towards better, more affordable BMW service in Melbourne starts with a simple phone call:

Alternatively, click here to get in touch online!