I was getting the "tiny leak - tighten gas cap" message and had the front purge valve replaced. Some months later the message returned, and I found a mouse had been grazing on the only rubber hose in the valve system. I patched the nibble, and the error went away. Months later... it came back, and I found there was a nibble from the first attack I had missed. So, I just decided to finally replace the rubber hose -- and that's when things got weird. All the other purge valve hoses are metal (anti-mouse?) and, indeed, INSIDE the one rubber hose (that goes TO the head) is also a metal hose (that goes INTO the head). The rubber hose is fixed off at one end by a tiny hose clamp, but at the other end it's just a very tight fit on the metal hose. So... what the hell is the purpose of the rubber hose as it's the metal hose that goes into the head? The rubber hose is clamped off before actually reaching the head. But it's a tight fit and I'd have to cut the existing hose off to replace... So, before I did thought I'd ask. Thanks!

 

Hard to say??

Can you post a couple of pictures to help?
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Thanks, club -- picture on the way. But was wondering if the metal "hose" inside the rubber hose might be perforated allowing the rubber hose to expand without releasing noxious gasses? Anyway, picture next but don't think it'll be much help.

 

OK, I asked an AI (actually two with similar results): You said

why is the metal hose of a purge valve inside a rubber hose

Copilot said

That design—where a metal or hard plastic hose is encased within a rubber hose—is actually quite intentional and serves multiple purposes in automotive systems like the EVAP purge valve:

🛡️ Protection & Durability

• Heat shielding: The rubber outer layer helps insulate the inner metal or plastic tube from engine heat, preventing premature wear or vaporization of fuel vapors.
• Chemical resistance: Rubber resists fuel and oil exposure better than some metals or plastics, adding a layer of defense against corrosion or degradation.

🔇 Vibration & Noise Dampening

• The rubber acts as a cushion, absorbing engine vibrations and road shocks. This prevents the rigid inner tube from cracking or transmitting noise into the cabin.

🧩 Structural Integrity

• The inner metal or plastic tube maintains a consistent internal diameter for proper vapor flow and vacuum pressure.
• It also prevents the hose from collapsing under vacuum, which could disrupt the EVAP system’s function.

🔧 Ease of Installation

• The rubber outer layer makes the hose more flexible, allowing it to be routed around tight engine compartments while the inner tube maintains its shape.

This dual-layer setup is a clever way to balance rigidity and flexibility, ensuring the purge valve system works reliably under tough conditions.

I guess... except the metal hose is not flexible at all.