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Autopapyrus · Nissan Terrano 1.6 H4M (2019)
https://autopapyrus.com/guides/nissan/terrano/exhaust-system-diagnosis-and-repair/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Nissan Terrano 1.6 H4M (2019): Exhaust System Diagnosis and Repair

The exhaust system on the Terrano with the H4M engine consists of the exhaust manifold, a downpipe with a flex joint, a catalytic converter, a center section, and a rear muffler on rubber hangers. Typical faults are a burned-through or cracked flex joint, leaking flanges, broken hangers, muffler corrosion, and a clogged catalytic converter. The repair starts with an accurate diagnosis, and then the damaged components are replaced.

Difficulty: Medium Time: 1.5-3 hours (depending on how corroded the fasteners are) Steps: 14

Parts

8
  • 🔩 Downpipe flex joint if faulty
  • 🔩 Downpipe flange gasket if faulty
  • 🔩 Catalytic converter if faulty
  • 🔩 Muffler (center and rear) if faulty
  • 🔩 Exhaust clamps if faulty
  • 🔩 Exhaust sealing rings if faulty
  • 🔩 Rubber hangers if faulty
  • 🔩 Oxygen (lambda) sensors (upstream and downstream of catalytic converter) for H4M if faulty

Tools

11
  • lift or inspection pit
  • socket and wrench set (mainly 13, 15, 17 mm)
  • ratchet
  • torque wrench
  • penetrating oil (such as WD-40)
  • high-temperature copper grease
  • wire brush
  • pry bar
  • oxygen sensor socket (slotted)
  • gloves
  • safety glasses
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes AutoFix (online). See manuals →

Step by step

14 steps
  1. Let the engine cool down completely. The system heats up to several hundred degrees, and you must not work on a hot exhaust system. Put the vehicle on a lift or over a pit with the parking brake applied.
  2. Diagnose by ear and by eye: start the cold engine and listen to the system. A hissing or puffing sound that gets louder when you press the accelerator points to a leak. Soot marks at the joints and on the pipes confirm where the leak is. If you are unsure, cover the tailpipe with a rag for a second or two, and the leak will become easier to hear (be careful, and do not do this without gloves).
  3. Inspect the system: check the downpipe flex joint for cracks, burn-through, and sagging, the flanges for soot traces, the muffler body for rust-through and dents, and the rubber hangers for tears and stretching. Shake the pipes by hand: the system must not touch the body or the underbody.
  4. If the Check Engine light is on or the engine has lost power, read the codes with an OBD scan tool. Codes related to the catalytic converter and oxygen sensors do not automatically mean the converter needs replacing. First make sure there are no air leaks in the system upstream of the sensor and that the sensors themselves are working properly.
  5. Prepare for removal: generously apply penetrating oil to all threaded connections and clamps and let it soak for 15-30 minutes. Rusty exhaust fasteners often snap, so do not apply excessive force.
  6. If you need to remove a section with an oxygen sensor, disconnect the sensor connector and unscrew the sensor with the slotted socket. Handle the sensors carefully: do not drop them, and do not get grease on the sensing tip.
  7. To replace the muffler or the center section: release the rubber hangers from their brackets (a pry bar and soapy water help), remove the flange fasteners or loosen the clamp, and lower the part down while supporting it so you do not damage adjacent sections.
  8. To replace the flex joint or the downpipe: remove the flange nuts at the manifold and the connection to the catalytic converter, then remove the pipe. If the flex joint has burned through, replace the entire downpipe (or the section as an assembly) instead of "fixing" the flex joint with clamps and tape, because that kind of repair is unreliable.
  9. Clean the flange mating surfaces with a brush to remove carbon deposits and rust. Use only new gaskets and sealing rings. Lightly coat the stud threads with heat-resistant copper grease so the nuts do not seize the next time.
  10. Reassemble in reverse order. First install the parts with the fasteners only snugged, not tightened. Align the system on the hangers so that nothing touches the body and the clearance is even, and only then tighten the fasteners in order from the engine to the rear muffler.
  11. Tightening torques: flange and manifold nuts approximately 20-30 N·m (15-22 lb-ft) (for M8-M10, the exact value depends on the joint, so check the manufacturer's specifications). Tighten clamps until they compress evenly without deforming the pipe. Oxygen sensor approximately 40-50 N·m (30-37 lb-ft).
  12. Connect the oxygen sensor connectors and check that the wires do not touch hot pipes and are secured in the factory holders.
  13. Start the engine and check each joint for leaks by listening, by holding a gloved hand near it (without touching hot parts), and by looking for smoke and soot. Warm up the engine, shut it off, and retighten the flanges once more after warm-up.
  14. Take a test drive: check for vibrations, rattles, and unusual noises over bumps. If any codes remain after the replacement, clear them with the scan tool and watch to see whether they return.

Common mistakes and warnings

  • Work only on a cooled exhaust system, and never run the engine in a closed garage: exhaust gases contain carbon monoxide (CO)
  • Do not drive the vehicle with a faulty catalytic converter or a burned-through flex joint: a leak upstream of the sensor distorts its readings and increases fuel consumption, and exhaust gases can enter the cabin
  • If you have no experience working under a vehicle on a lift, leave the repair to a repair shop