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Crankcase Vent (PCV) Valve – Symptoms, Diagnostics and More

Crankcase Vent Valve - Symptoms, Diagnostics and More

BMWs are often described as high value, high maintenance cars. Owning and driving one is a blast, that’s for sure. However, it’s no secret that your average BMW relies on a fairly complex and tight-knit network of subsystems that have to work flawlessly for that car to perform as advertised. The elusive crankcase vent valve, also known as the PCV valve, is part of one such system.

It’s a relatively simple device that can cause a whole array of symptoms and put your BMW out operation for a while. Understanding the symptoms and recognizing a failing CCV can save you plenty of headaches. Our goal in this guide is to arm you with the information necessary to spot CCV issues on your car long before they become an issue. Grab yourself a cup of coffee, and let’s get down to it.  

What is a Crankcase Vent Valve on E60, E46, E39, and Other Models?

Your average internal combustion engine is a marvelous feat of engineering. A lot is going on inside that metal contraption that harnessing explosives 9,000 times every minute. The top part where the pistons are is taking the brunt of the force and transferring that energy to the crankshaft down below. In a perfect world, the crankcase and the cylinders would be two wholly isolated systems. However, that’s not quite possible in real life.

It all has to do with the amount of pressure that is being inside each of your cylinders. As the engine goes through its four cycles, the gasses inside the cylinder are mercilessly compressed. Before the engine reaches the exhaust cycle, some of those gases slip by the piston rings and connecting rods, ending up in the crankcase.  

Although not perfect, this small amount of blow-by is perfectly normal and manageable. That being said, if this buildup of gasses is left unattended, it could cause all kinds of issues inside the crankcase. An average crankcase is a closed system. You’ve got gaskets and seals that prevent anything from getting in there and getting out. Gasses building up inside would eventually reach a critical point and blow a gasket at the very least.

That is why BMW and many other car manufacturers install crankcase ventilation valves, also known as CVV or PCV valves. Having a ventilation system in place to evacuate blow-by gasses from the crankcase in a controlled manner is a great way to keep everything balanced. 

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The M54 and M52TU Shenanigans

Every engine out there, no matter how bulletproof, has that one potential known issue. Exploitation over time is the perfect way to flush out any problems on an engine. One thing all of us grew to like about BMW is that these issues are rarely major. You won’t find defective engine blocks or crankshafts that just love to snap in two. With BMW, it’s the small stuff.

For example, the M54 and M52TU became notorious for CVV issues. At first, it seemed like a sporadic issue that some owners were experiencing. However, as time went on, and these cars started pushing 5 to 6 figure miles on the clock, it became apparent that the CVV issue was nothing short of a defect.

You’d see M54 engines with a failed CVV that had 60,000 miles on the clock. That’s pretty serious, especially considering the type of services the resulting problems would need. The same thing happened with M52TU. The issue became so bad that most BMW specialists started recommending preventative servicing of the CVV system.

Why Does the Crankcase Vent Valve Fail?

The CVV setup on these engines, and most other BMW engines, consists of a series of ventilation and drain hoses, an oil separator and the valve itself. Although the system itself is simple, it still includes a decent amount of components.

How and why does it fail, though? The way the whole setup is designed makes it vulnerable in several ways. For starters, the vacuum and oil drain hoses are known to crack over time. This is caused by continually changing temperature within the engine bay, subpar rubber compounds, and more. Then the valve itself could fail. Finally, you might experience a buildup of sludge in the oil drain hose, which can clog everything up, causing the system to fail.

Recognizing the Symptoms of a Failing or Failed Crankcase Ventilation Valve

Now that we know the CVV might fail, how do we recognize the symptoms? Often overlooked or associated with other issues, signs of a failing CVV are pretty diverse. Here are some of the most common ones.

Oil Consumption

Checking your car’s oil levels is something you should do on a semi-regular basis. Just about every engine consumes oil, some more than others. If you notice that your engine is consuming more oil than usual, that could be due to a failed CVV. Be sure to check the dipstick every once in a while.

Rough Idle

One of the most common symptoms is a rough idle. How rough it gets will depend on the severity of the problem, but it can definitely get very, very rough. As the CVV and all of its hoses clog up, some of the oil sludge might get routed to the intake via one of the connecting lines. If you notice the rough idle and the diagnostics show that everything else is fine, make sure to check the CVV.

Check Engine Light

The ominous orange symbol of impending doom is also on the list of symptoms for a failing or failed crankcase ventilation valve. It is often triggered by the fuel trim being out of whack, which the ECU will promptly report when hooked up to an OBD reader. As always, don’t ignore the check engine light.

Complete Engine Failure

This why this issue can’t be ignored. If you do, you’re risking enough moisture and oil residue being sucked into the engine through the intake and causing all kinds of damage. The crankcase vent valve is not something you want to ignore.

Crankcase Vent Valve - Symptoms, Diagnostics and More

The Solution

Replacing the CVV on any BMW engine is a pain in the rear. The replacement process is fairly straightforward. However, it’s reaching the valve that’s the main issue. You’ll have to disassemble a good chunk of the intake system and more only to get to the valve. Much like other sources out there, we suggest doing preventative replacement of this part.

The Cold Weather Kit

The most proven solution right now is the installation of the so-called cold weather kit. This is essentially a type of CVV system that was designed for colder climates. All of the cars with the M54 and M52TU engines sold in the United States arrived with the warm weather system installed. The main difference between the two is insulation, which the cold weather kit has. Insulation alone can prevent most of the issues with hoses and vacuum lines.

Getting the cold weather kit should keep you going for at least 50,000 miles. Again, if you’re up to the task of DIY-ing this, you’re well ahead of the curve. Otherwise, it’s a time-consuming repair that can rack up man-hours before your car is back to its usual self again.

Check out our online store for a complete list of replacement parts. All you have to do is input your car’s year, make and model or type in your VIN. Our system will crunch the info and show you all of the matching parts! 

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