Proper hose routing in a Nashville catch can system directly affects how well the unit separates oil mist and crankcase pressure from entering the intake tract. A carefully planned layout prevents vacuum leaks, avoids unnecessary strain on fittings, and makes periodic draining and inspection straightforward. This guide covers the principles behind a well-routed system, details the best practices for hose placement, and highlights common errors that can compromise performance.

Understanding the Nashville Catch Can System

The Nashville catch can is a passive oil-air separator installed between the crankcase ventilation outlet and the intake manifold or air intake. As blow-by gases exit the engine, the can forces a rapid change in direction and velocity, causing heavier oil droplets and moisture to fall out of suspension and collect in the bottom of the can. Cleaner air then returns to the intake, reducing carbon buildup on valves and intercooler components.

The system relies on three primary hose connections: the inlet from the crankcase (often from the valve cover or PCV valve), the outlet to the intake manifold (or intake tube for naturally aspirated applications), and in some setups a drain line back to the oil pan. Routing these three paths correctly is essential because any kink, pinch, or heat damage can create a restriction, unseating the can’s internal baffling or causing the crankcase pressure to spike.

Because the Nashville catch can is often installed in tight engine bays, the routing path must account for body panels, heat shields, and moving suspension components. A hose that rubs against a bracket or lies too close to an exhaust manifold will wear through quickly, leading to an undetected vacuum leak that can lean out the air-fuel mixture. A good routing plan begins with understanding the flow direction and then mapping the shortest, most protected path between connections.

Why Hose Routing Matters

Even a high-quality catch can performs poorly if the hoses force the gases through sharp turns or long, unvented loops. Excessive hose length adds volume that slows the gas velocity, reducing separation efficiency. Each unnecessary foot of hose also increases the chance of oil pooling in low spots, which can later be sucked into the intake under hard acceleration.

Incorrect routing can also interfere with the PCV system’s designed pressure differential. For example, if the outlet hose is routed uphill without a check valve, condensed oil may drain back into the can or even into the intake manifold when the engine is off. On turbocharged engines, routing the wrong hose to the intake side before the turbo can cause oil to enter the compressor housing. Proper routing ensures that the catch can operates in the correct flow direction, at the right pressure, and with minimal restriction.

Beyond performance, good routing makes maintenance easier. A Nashville catch can needs periodic draining—typically every 1,000 to 3,000 miles depending on driving conditions. If the drain hose is tucked behind a bracket or the collection chamber is hard to access because hoses block the lid, the owner is likely to skip the service, leading to overflow and system contamination. Proper routing always prioritizes serviceability.

Best Practices for Routing Hoses

Following each of these practices will produce a reliable, long-lasting installation. Neglecting even one area can undo the benefits of the others.

Use High‑Quality Hoses

Not all rubber or silicone hoses are suitable for crankcase ventilation. The hose must resist oil degradation, ozone, and under‑hood temperatures that can exceed 250°F. SAE J30R7 or equivalent oil‑resistant rubber works for naturally aspirated engines, but for turbo builds or cars that see track time, reinforced silicone hoses rated for 300°F+ are a better choice. Avoid thin walled vacuum hoses; they collapse under high crankcase pressure and can restrict flow. Braided stainless or nylon overbraid adds abrasion resistance in high‑wear areas.

Avoid Sharp Bends and Kinks

Every hose has a minimum bend radius. A 90‑degree turn that is too tight flattens the inner wall, creating a pinch that acts like a valve—raising crankcase pressure and forcing oil past the piston rings. Use pre‑formed silicone elbows, or route hoses in a sweeping curve with at least a 3‑inch radius for 3/8″ or 1/2″ ID hoses. If a sharp turn is unavoidable, install a smooth‑flow fitting (such as a 45‑ or 90‑degree AN fitting) at the can or engine port to change direction without pinching the hose wall.

Secure Hoses Firmly

Vibration and engine movement can cause hoses to work loose over time. Use constant‑tension spring clamps or worm‑gear clamps on every barbed fitting, and position them so they do not contact adjacent hoses. Where hoses run alongside frame rails or the inner fender, add P‑clamps or nylon zip ties with rubber cushions every 12–18 inches. This prevents chafing and keeps the hose from sagging into hot or moving parts.

Maintain Proper Hose Length

Cut each hose to the shortest possible length that allows a smooth route without tension. Excess slack can droop and create low points that collect oil; too little slack causes the hose to pull on fittings, eventually loosening them. A good rule: leave about 1–2 inches of extra length beyond the measured path to account for engine rock, but trim away any loop or sag. For drain lines, maintain a continuous downward slope from the can to the drain point (if a drain back to the oil pan is used).

Follow Manufacturer Routing Diagrams

Nashville catch can systems come with a specific hose routing diagram that indicates which port is the inlet, which is the outlet, and whether a check valve or restrictor is needed in the line. Deviating from the diagram can reverse the flow direction inside the can, dumping oil directly into the intake. Always reference the included documentation or contact the manufacturer’s tech line if you are unsure about port labeling.

Route Hoses Away from Heat Sources

Exhaust manifolds, turbochargers, EGR tubes, and radiator hoses all emit significant heat. Keep all catch can hoses at least 6 inches away from these sources whenever possible. If a hose must cross near a hot surface, wrap it with reflective heat shield tubing (e.g., DEI Cool‑Tube or a silicone‑impregnated fiberglass sleeve). Heat accelerates rubber degradation and can cause the inner lining to shed particles that clog the can’s baffles.

Step‑by‑Step Routing Guide

Although every engine bay is different, this general sequence helps ensure a clean and functional installation.

  1. Identify the crankcase ventilation port(s). On most engines this is a 3/8″ or 1/2″ fitting on the valve cover or a dedicated PCV valve. Check the orientation and note whether the fitting is straight or angled.
  2. Mount the catch can in a stable, low‑vibration location that is accessible for draining. Common spots are the inner fender wall, a strut tower brace, or a fabricated bracket near the firewall. Ensure the can is oriented upright (inlet and outlet ports at the top) unless the manufacturer specifies otherwise.
  3. Measure the inlet hose path first. Use a piece of string or flexible wire to trace the shortest route from the crankcase port to the can’s inlet, avoiding heat sources and moving parts. Add 2 inches for clamp allowance and cut the hose to exactly that length.
  4. Connect the inlet hose to the crankcase port and the can’s inlet barb. Use a clamp on each end. Double‑check that the hose does not touch the engine block or frame where it could chafe.
  5. Route the outlet hose from the can’s outlet to the intake manifold (or to the intake pipe before the turbo). Many setups require a one‑way check valve in this line; install it with the flow arrow pointing toward the intake. Keep this hose as short as possible—preferably under 12 inches—to minimize pressure drop.
  6. If using a drain‑back line, route it from the can’s drain port (typically at the bottom) to the oil pan. Use hose rated for constant oil submersion, and ensure a continuous downhill slope with no sags or low loops.
  7. Secure all hoses with clamps and zip ties as described in the best practices section. Operate the engine through a full heat cycle, then re‑check all connections for leaks and clearance.

Common Mistakes and How to Avoid Them

Mistake 1: Overtightening Clamps

A worm‑gear clamp tightened beyond snug can dig into the hose wall, causing a bulge that leaks or splits over time. Use a torque‑limiting screwdriver or tighten only until the clamp seats firmly—usually 1/4 to 1/2 turn after contact.

Mistake 2: Routing Hoses Near Hot Components

As mentioned, proximity to exhaust headers or turbo housings bakes the hose. Even with heat wrap, check clearance after a hard drive; a hose that has softened might droop onto a hot surface. Reroute or add a rigid heat shield if the hose cannot be moved.

Mistake 3: Using Low‑Quality Hoses

Cheap silicone or rubber with poor oil resistance can turn gummy or crack within months. Invest in hoses from reputable manufacturers such as Mishimoto or UPR Products that specifically list compatibility with crankcase ventilation oils and temperatures.

Mistake 4: Ignoring Regular Maintenance

A clogged catch can will not separate oil effectively. Drain the can every 1,000–3,000 miles, or more often in cold climates where moisture accumulation is high. Inspect hoses for swelling, cracks, or signs of abrasion at each oil change. Clean or replace the internal baffle media per the manufacturer’s schedule.

Mistake 5: Reversing Inlet and Outlet

Some catch can designs have the inlet and outlet visually identical. Always check the labeling or the internal baffle direction. Installing the hoses backward blows oil straight through the can, bypassing the separation chamber. Mark the ports with colored tape during installation to avoid confusion later.

Tools and Materials Needed

  • Hose cutter or sharp utility knife
  • Worm‑gear or spring clamps sized for the hose diameter
  • P‑clamps and nylon zip ties
  • Reflective heat shield sleeve (if routing near hot components)
  • Check valve (if required by system)
  • Flathead and Phillips screwdrivers, socket set for mounting bracket
  • String or flexible wire for measuring path

Troubleshooting Hose‑Routing Issues

If you notice excessive oil consumption, rough idle, or the catch can filling unusually fast after installation, check these items in order:

  1. Hose pinches—run your hand along the entire length of both hoses while the engine is idling. A collapsed section will feel cooler than the rest. Reshape or replace that section.
  2. Loose clamps—smell underhood for oil vapor. Tighten any clamp that shows signs of weeping.
  3. Incorrect check‑valve orientation—if the engine stalls when you disconnect the outlet hose, the check valve may be blocking flow. Verify arrow direction.
  4. Heat damage—a hose that has become brittle or has blistered spots must be replaced and rerouted.
  5. Sludge in the can drain line—if the drain back line is uphill or has a low loop, oil pools and turns to sludge. Clear the line and reroute with a constant downward slope.

For more detailed diagnostics, consult the engine tuning community or EngineLabs for case studies on catch can installations.

Conclusion

Effective hose routing in a Nashville catch can system goes beyond simple aesthetics. It ensures the can operates at its design flow, prevents costly engine damage from oil ingestion, and simplifies the maintenance that keeps the system working. By choosing quality heat‑ and oil‑resistant hoses, planning a smooth path that avoids sharp bends and hot surfaces, and securing every connection properly, you can enjoy cleaner intake valves, reduced knock, and longer engine life. Take the time to route each hose with care—the engine will repay you with consistent performance for thousands of miles.