Exhaust Gasket - Rear

This procedure covers replacement of the rear exhaust gasket on the 3.5L EcoBoost V6, which connects the catalytic converter or mid-pipe to the rear exhaust section.

Warnings

Tools required

Parts

• Rear exhaust flange gasket × 1 — Use OEM specification or Felpro equivalent
• Exhaust flange bolts (if corroded) × 4 — M10 x 1.5 x 35mm

Preparation

1. Park vehicle on level ground and engage parking brake
2. Place wheel chocks at front wheels
3. Ensure exhaust system has cooled completely (minimum 2 hours after operation)
4. Raise rear of vehicle to comfortable working height and support on jack stands at frame rails
5. Spray all exhaust flange bolts and hanger bolts with penetrating oil and allow to soak for 15 minutes

Procedure

1. 1

   Locate rear exhaust flange connection
   Position yourself under the vehicle near the transmission area. Locate the rear exhaust flange connection, which joins the catalytic converter/mid-pipe section to the rear muffler assembly. This is typically positioned just behind the transmission crossmember.
2. 2

   Remove heat shield if present
   If a heat shield covers the flange connection, remove the mounting bolts using a 13mm socket. There may be 2-4 bolts depending on configuration. Set heat shield aside.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
3. 3

   Support rear exhaust section
   Have a helper support the weight of the rear muffler section, or use a jack stand with a block of wood to support the rear exhaust assembly. This prevents stress on the hangers and allows easier flange separation.
4. 4

   Remove rear exhaust hanger bolts
   Locate the rubber exhaust hangers supporting the rear section. Remove the hanger mounting bolts using a 15mm socket to provide additional movement for flange access. Typically there are 1-2 hangers near this connection point.
   Torque spec

   Hanger Bolts23 Nm (17 lb-ft)
5. 5

   Remove exhaust flange bolts
   Using a 15mm socket with extension, remove all bolts from the rear exhaust flange (typically 4 bolts in a square pattern). Apply steady pressure to avoid rounding bolt heads. If bolts are severely corroded and break, use a drill and extractor set or cut them off and replace.
   ⚠If bolts break during removal, the flange studs may need to be drilled out or replaced. Plan extra time if corrosion is severe.
6. 6

   Separate exhaust flange
   Pull the rear exhaust section rearward to separate the flange connection. If stuck due to carbon buildup, gently twist while pulling. Remove the old gasket from both flange surfaces.
7. 7

   Clean flange surfaces
   Use a wire brush to thoroughly clean both exhaust flange mating surfaces, removing all carbon deposits, old gasket material, and corrosion. Both surfaces must be completely clean and flat for proper sealing. Wipe clean with a rag.
8. 8

   Install new gasket
   Position the new exhaust gasket onto the forward flange (catalytic converter or mid-pipe side). Ensure the gasket is centered and properly aligned with all bolt holes. Some gaskets have an orientation tab or marked side.
9. 9

   Reconnect exhaust flange
   Carefully align the rear muffler flange with the forward flange and new gasket. Push sections together ensuring gasket remains properly positioned. Have helper support weight or adjust jack stand as needed.
10. 10

    Install and torque flange bolts
    Apply anti-seize compound to the threads of new or reused flange bolts. Install all bolts finger-tight, then tighten in a cross pattern (top-left, bottom-right, top-right, bottom-left) to ensure even gasket compression. Torque to specification using the cross pattern.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)
11. 11

    Reinstall exhaust hangers
    Align the rubber exhaust hangers with their mounting brackets and install hanger bolts. Torque to specification. Ensure exhaust is properly positioned with adequate clearance from fuel lines, brake lines, and chassis components.
    Torque spec

    Hanger Bolts23 Nm (17 lb-ft)
12. 12

    Reinstall heat shield
    If heat shield was removed, position it back over the flange connection and install mounting bolts. Torque to specification.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)

Reassembly

1. Verify all exhaust hangers are properly seated and supporting the exhaust system
2. Check entire exhaust system for proper routing with no contact points against chassis or fuel/brake lines
3. Remove jack stands and lower vehicle to ground

Verification

• Start engine and allow to idle. Listen for exhaust leaks at the rear flange connection - there should be no hissing or ticking sounds
• Visually inspect flange connection while engine is running for any visible exhaust gas escaping
• After 5 minutes of operation, re-check flange area for leaks as components expand with heat
• Take vehicle for short test drive and verify no exhaust smell in cabin and no unusual sounds from rear exhaust section
• After test drive, perform final inspection of flange connection and verify all bolts remain tight

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