If you're tired of seeing that oily mess inside your intake, it's probably time to look into an lbz pcv reroute kit. Anyone who has owned a 2006 or 2007 Duramax for more than a few months knows exactly what I'm talking about. You pop off an intercooler boot to do some routine maintenance, and instead of a clean pipe, you find a thick coating of black, oily sludge. It's annoying, it's messy, and honestly, it's not doing your engine any favors in the long run.
The Positive Crankcase Ventilation (PCV) system on the LBZ was designed with good intentions—mostly to keep emissions down—but the execution leaves a lot to be desired for the guy actually driving the truck. By venting those oily crankcase vapors right back into the turbo inlet, GM essentially turned your intake tract into a grease trap. This is why the lbz pcv reroute kit has become such a staple for diesel enthusiasts. It's one of those "day one" mods that just makes sense if you plan on keeping your truck for a long time.
Why the factory setup is a headache
To understand why you need to reroute things, you have to look at what's happening inside the engine. Every internal combustion engine has blow-by—it's just a reality of physics. Some of the combustion gases sneak past the piston rings and end up in the crankcase. These gases are hot and carry a fine mist of engine oil with them. In the old days, trucks just had a "draft tube" that hung down and let this stuff vent to the atmosphere.
With the LBZ, though, that mist is sent into the intake. When that hot oil vapor hits the relatively cooler surfaces of your intercooler and the plumbing, it condenses. Over thousands of miles, that oil builds up. But the real problem starts when that oil meets the soot coming from the EGR system. When you mix oil mist with dry soot, you get a nasty, thick sludge that looks like half-dried asphalt. This junk coats the inside of your intake manifold, reduces airflow, and can eventually cause all sorts of sensor issues. Installing an lbz pcv reroute kit stops this cycle before it even starts.
What actually comes in the kit?
Most of these kits are pretty straightforward, which is part of their appeal. You don't need a degree in mechanical engineering to figure out what's going on. Usually, you're looking at a couple of billet aluminum plugs for the turbo mouthpiece, some heavy-duty hose, a T-fitting, and the necessary clamps to keep everything tight.
The goal is simple: you plug the holes where the PCV system used to enter the intake, and then you run a new line from the valve covers down toward the frame rail. This allows the engine to breathe without dumping its "exhaust" back into its own lungs. Some guys choose to run the hose into a catch can, while others just let it vent to the atmosphere under the truck. Either way, the internal components of your engine stay a whole lot cleaner.
The performance side of things
While a PCV reroute isn't going to give you a massive jump in horsepower like a high-end tune or a bigger turbo would, it definitely helps with overall efficiency. When your intercooler is coated in oil, it can't dissipate heat as well. High intake air temperatures (IATs) are the enemy of diesel performance. By keeping the intercooler clean with an lbz pcv reroute kit, you're ensuring that your cooling system is working at its peak potential.
Another huge benefit that people often overlook is the health of your boots. Those rubber or silicone couplers that hold your intercooler piping together hate oil. Over time, the oil saturates the material, making it soft and spongy. If you're running higher-than-stock boost levels, those oil-soaked boots are the first things to fail. They'll either slip off under pressure—which sounds like a literal gunshot when it happens—or they'll eventually tear. Keeping the oil out of the system means your boots stay dry and grippy, which is one less thing to worry about when you're pulling a heavy trailer up a grade.
Tips for a smooth installation
If you're planning on doing this in your driveway, it's a pretty manageable job, but there are a couple of things that can make it easier. First off, the area near the firewall can be a bit tight. You're going to be working around the back of the engine where the factory PCV hoses connect to the valve covers. It helps to have a good set of pliers or even a long-reach pick to get those factory spring clamps off. They can be stubborn, especially if they've been sitting there since 2006.
When you're routing the new hose, make sure you keep it away from the exhaust manifold. It sounds like common sense, but things get crowded back there, and you don't want your new vent line melting to your downpipe. I usually like to zip-tie the hose along the frame rail, making sure there are no kinks. If the hose gets pinched or kinked, pressure can build up in the crankcase, which might lead to oil leaks at your main seals. You want that vapor to flow out as freely as possible.
Is it worth the effort?
In my opinion, absolutely. For the price of a decent dinner, an lbz pcv reroute kit offers some of the best "peace of mind" insurance you can buy for a Duramax. It's a permanent solution to a design flaw that affects almost every diesel engine from that era. You'll notice that after the install, your intake stays dry, your turbo stays cleaner, and you won't have that annoying oil drip coming from your intercooler boots onto your driveway.
Some people worry about the smell, as venting to the atmosphere can sometimes result in a slight "old truck" scent when you're idling at a stoplight. To be honest, most people don't even notice it. If you have a sensitive nose, you can always route the hose further back toward the rear axle, or better yet, install a catch can with a filter. That way, you get all the benefits of the reroute without any of the smells.
Final thoughts on the upgrade
It's rare that such a simple modification can have such a long-lasting impact on an engine's longevity. The LBZ is widely considered one of the best Duramax engines ever made, mostly because it avoided a lot of the more complex emissions equipment found on later models. Adding an lbz pcv reroute kit is just another way to lean into that reliability.
By taking the time to set this up, you're basically ensuring that the air going into your engine is as clean as possible. You're protecting the turbo compressor wheel from oil buildup, keeping the intercooler efficient, and preventing that nasty sludge from clogging up your intake runners. It's a win-win all around. So, if you've been putting it off or just noticed some oil weeping from your boots, go ahead and pull the trigger on a kit. Your truck—and your mechanic—will definitely thank you later.