2018 Chrysler 300 5.7L HEMI - Exhaust Smell in Cabin & Louder Exhaust

ClearTheCode admin answer:

An exhaust smell in the cabin, combined with a louder exhaust noise (especially a ticking or hissing when cold), is a classic symptom of an exhaust leak on your 2018 Chrysler 300C with the 5.7L HEMI engine. You're right to be concerned, as exhaust fumes contain carbon monoxide, which is dangerous.

Here are the most common causes and what to check:

1. Exhaust Manifold Leaks (Broken Bolts):

   • Cause: This is an extremely common issue on HEMI engines. The exhaust manifold bolts (especially on the passenger side) are prone to breaking due to heat cycles, causing the manifold to pull away from the cylinder head. This creates a leak that's often most noticeable when the engine is cold and metal components are contracted. The ticking/hissing sound is the exhaust escaping.
   • Action: Visually inspect the exhaust manifolds for signs of black soot around the manifold-to-head mating surface. Pay close attention to the bolts – look for missing or broken bolt heads. This often requires removing the wheel well liner for better access.

2. Cracked Exhaust Manifold:

   • Cause: Less common than broken bolts, but the manifold itself can crack due to thermal stress, creating a similar leak.
   • Action: Look for visible cracks on the manifold casting, especially around the welds or flange areas.

3. Exhaust Pipe/Gasket Leaks:

   • Cause: Leaks can occur at any connection point in the exhaust system, such as:
     • Between the manifold and the catalytic converter (donut gasket).
     • At muffler or resonator connections.
     • Cracks in the exhaust pipes themselves.
   • Action: Inspect the entire exhaust system from front to back for rust holes, loose clamps, or damaged gaskets. You can sometimes feel exhaust gas escaping with your hand (carefully, when cold) or listen for the distinct 'puffing' sound.

4. Flex Pipe Failure:

   • Cause: If your exhaust system has a flexible section (flex pipe) to absorb engine movement, it can wear out and develop leaks.
   • Action: Inspect the braided mesh section of the flex pipe for damage or signs of exhaust leakage.

When to see a shop:

• Immediately if the exhaust smell is strong and persistent, as carbon monoxide is odorless and deadly.
• If you confirm broken exhaust manifold bolts, as removal can be tricky and sometimes requires specialized tools (e.g., stud extractors) or drilling.
• If you're unable to locate the source of the leak yourself.
• Anytime you're uncomfortable working around a hot engine or exhaust system.

Driving with an exhaust leak is not only annoying but also a health hazard. Get this checked out as soon as possible.