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Autopapyrus · Mazda CX-5 (KF, 2nd generation) 2.0 SKYACTIV-G (2024)
https://autopapyrus.com/guides/mazda/cx-5/exhaust-downpipe-flex-joint-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Mazda CX-5 (KF, 2nd generation) 2.0 SKYACTIV-G (2024): Exhaust Downpipe Flex Joint Replacement

The flex joint in the downpipe absorbs vibration from the powertrain. When it wears out, you get a loud exhaust under the floor, hissing or ticking on a cold engine, exhaust smell in the cabin, and sometimes vibration in the body. The exact procedure for this model is only covered to a limited extent in publicly available service information, so what follows is the general approach proven on SKYACTIV-G engines. The flex joint is usually permanently attached to the downpipe, so in practice you either replace the whole assembly or cut out the flex joint and install a repair insert.

Difficulty: Hard Time: 2-4 hours (allowing for seized fasteners) Steps: 14

Parts

5
№PartAlternatives
01 Exhaust downpipe flex joint, 2.0 SKYACTIV-G
02 Downpipe with flex joint, completeif the flex joint is not sold separately
03 Downpipe flange gasket
04 Self-locking flange nuts/bolts
05 Stainless steel repair flex joint (clamp-on or weld-in)repair option Walker, Bosal, Polmostrow

Tools

10
  • Lift or inspection pit
  • jack with jack stands
  • socket and wrench set 12-17 mm
  • torque wrench
  • penetrating oil (such as WD-40)
  • oxygen sensor socket or sensor remover
  • angle grinder or pipe cutter (for the cut-in option)
  • welder (if the flex joint is welded)
  • copper anti-seize for exhaust studs
  • multimeter or OBD scanner
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes AutoFix (online) and 1 more. See manuals →

Step by step

14 steps
  1. Confirm the diagnosis. With the engine cold, inspect the flex joint: cracks in the braid, pinholes, and soot marks around it. You can also listen for the leak with a hose and stethoscope. Make sure the noise is not coming from a flange gasket or the resonator.
  2. Let the exhaust system cool completely (at least 1-2 hours after driving). Put the vehicle on a lift or on jack stands on level ground, and chock the wheels.
  3. Disconnect the negative battery terminal. Remove the lower engine undercover and, if it is in the way, the downpipe heat shield.
  4. Apply penetrating oil to all flange nuts and bolts and wait 10-15 minutes. Exhaust threaded connections tend to seize, so take your time.
  5. Disconnect the oxygen sensor connectors (upstream and downstream of the catalytic converter) if they are located on the section being replaced. Remove the sensors with an oxygen sensor socket if their mounting bosses come off with the pipe. A damaged sensor will need to be replaced.
  6. Support the exhaust system under the resonator/muffler (with a stand or strap) so you do not tear the hangers.
  7. Remove the hanger rubbers near the flex joint (pry them off with a pry bar, lubricating them with soapy water).
  8. Remove the nuts on the downpipe flange at the catalytic converter/manifold and the flange to the underfloor section of the system. Tighten to the manufacturer's specification; for flanges like these, 30-50 N·m (22-37 lb-ft) is typical (check the exact value in the service manual).
  9. Remove the assembly. For the complete-assembly option: install the new downpipe with the flex joint using new flange gaskets, without misalignment, so the flex joint is not compressed or twisted.
  10. For the repair flex joint option: cut out the damaged section, straight and perpendicular to the pipe axis, keeping the correct insert length. Weld in the flex insert. If you have no welder, a clamp-on insert is acceptable, but it is only a temporary fix.
  11. Tighten the flanges in a crisscross pattern in two stages, then finish with a torque wrench. Tighten with the system unloaded and the flex joint not bent.
  12. Install the sensors, connect the connectors, and refit the heat shield and hanger rubbers. Reconnect the battery.
  13. Start the engine and check for leaks (with a gloved hand, or with soapy water while the system is cold; do not inhale exhaust fumes from leaks). If an oxygen sensor fault code appears, read it with a scanner and clear it.
  14. Take a test drive of 10-15 km, then re-tighten the fasteners after the system cools.

Common mistakes and warnings

  • Never bend or stretch the flex joint, or use it as a lever during installation: it will fail quickly
  • Do not work on a hot system: risk of burns and fire
  • Do not breathe exhaust gases in an enclosed space
  • If welding is required and you lack experience, leave the job to a repair shop
  • When working under a raised vehicle, use only jack stands, never jacks alone