How to Remove the Exhaust Manifold on a 2004 Mazda 6 3.0 Liter

The 2004 Mazda 6S came with a 3.0-liter six-cylinder and a five-speed manual transmission. The 3.0-liter has two exhaust manifolds; one for the left cylinder head and one for the right. Your exhaust manifolds have the catalytic converters built into them, so replacing either exhaust manifold with anything except an OE-style part will cause you to fail emissions testing and may cause performance problems. The process for removing either side is almost the same, but will require a special tool to remove the oxygen sensors.

Instructions

Removal

1

Park the vehicle on a level surface and set the parking brake. Lift the vehicle hood and support it with the hood prop rod. Lift the front of the vehicle into the air with the floor jack and place the jack stands under the front subframe. Lower the floor jack until the vehicle rests securely on the jack stands. Allow the engine to cool completely before continuing.

2

Remove the oil fill cap and set it aside. Lift up on the corners of the engine cover carefully to remove the engine cover from the engine, and set it aside. Install the oil filler cap. Loosen the air intake tube clamps at the throttle body and mass air flow sensor with the socket and ratchet. Remove the air intake tube from the engine area.

3

Trace the oxygen sensor pigtail for both manifold mounted sensors back to where they connect to the engine wiring harness. Squeeze the locking tab and pull the connectors apart. Remove the oxygen sensors from the exhaust manifolds with the oxygen sensor socket and ratchet. Apply heat with the propane torch to the base of the sensor mounting area if the sensors will not loosen easily. Set the oxygen sensors aside.

4

Loosen the fitting for the exhaust gas recirculation tube on the right exhaust manifold and EGR valve with the line wrench. Remove the EGR tube and set it aside. Loosen, but dont remove the nuts securing the exhaust manifolds to each cylinder head with the socket and ratchet. Loosen the far right bolt on the right exhaust manifold with the box-end wrench.

5

Lay down under the vehicle and follow the exhaust system forward to where it meets the exhaust manifolds. Remove the exhaust manifold to down pipe nuts with the socket and ratchet.

6

Remove the left exhaust manifold nuts and set them aside. Pull the left exhaust manifold away from the engine slightly and lift it out of the engine bay. Remove the left exhaust manifold and manifold to downpipe gaskets.

7

Remove the right exhaust manifold nuts and set them aside. Loosen the far right exhaust manifold bolt enough to separate the bolt from the cylinder head with the box-end wrench. Tilt the right exhaust manifold away from the alternator bracket and lift it away from the downpipe. Remove the far right bolt from the exhaust manifold.

Installation

8

Place one exhaust manifold mounting bolt into the far right hole on the right exhaust manifold and set the new exhaust manifold gasket into place. Slide the right exhaust manifold behind the alternator bracket and into position. Install the remaining right exhaust manifold bolts loosely.

9

Set the left exhaust manifold gasket into place and lower the exhaust manifold to the exhaust downpipe. Install the left exhaust manifold bolts loosely.

10

Lay down under the vehicle and install the manifold to downpipe gaskets over both exhaust manifold studs. Maneuver the downpipe onto each exhaust manifold and install the retaining nuts. Tighten the manifold to downpipe nuts to between 29 and 37 foot-pounds with the torque wrench.

11

Tighten the left exhaust manifold bolts to 14 to 19 foot-pounds in the following sequence: top center, bottom center, bottom left, top right, top left and bottom right. Tighten the right exhaust manifold bolts to 14 to 19 foot-pounds in the following sequence: Top center, bottom center, bottom right, top left, top right and bottom left.

12

Install the EGR tube to the EGR valve and exhaust manifold; tighten the fittings to between 26 and 33 foot-pounds. Clean the oxygen sensor threads with the wire brush and then coat the oxygen sensor threads with the anti-seize compound. Install the oxygen sensors into the exhaust manifolds. Tighten the oxygen sensors to 22 to 35 foot-pounds with the torque wrench and oxygen sensor socket.

13

Install the air intake tube onto the throttle body and mass air flow sensor. Tighten the clamps with the socket and ratchet. Remove the engine oil fill cap and set the engine cover into position. Tap lightly over the engine cover to secure it into place. Install the oil filler cap.

14

Lift the front of the vehicle off the jack stands with the floor jack. Remove the jack stands from under the vehicle. Lower the vehicle to the ground and remove the floor jack.