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Exhaust manifold - removal, inspection and refitting
In-car engine repair procedures / Exhaust manifold - removal, inspection and refitting


Warning: The engine must be completely cool before beginning this procedure.

Note: In addition to the new gasket and any other parts, tools or facilities needed to carry out this operation, a new plastic guide sleeve will be required on reassembly.

Removal
1 Disconnect the battery negative (earth) lead - see Chapter 5, Section 1.

2 Unbolt the resonator support bracket from the engine compartment front crossmember, slacken the two clamp screws securing the resonator to the air mass meter and plenum chamber hoses, then swing the resonator up clear of the thermostat housing (see Chapter 4).

3 Drain the cooling system (see Chapter 1).

4 Disconnect the coolant hose and the coolant pipe/hose from the thermostat housing; secure them clear of the working area.

5 Unbolt the exhaust manifold heat shield, and withdraw both parts of the shield (see illustration). Apply penetrating oil to the EGR pipe sleeve nut, and to the exhaust manifold mounting nuts (also to the pulse-air system sleeve nuts, if they are to be unscrewed).

7.5 Exhaust manifold heat shield upper part securing bolts (arrowed)
7.5 Exhaust manifold heat shield upper part securing bolts (arrowed)

6 Unscrew the sleeve nut securing the EGR pipe to the manifold, remove the two screws securing the pipe to the ignition coil bracket, then slacken the sleeve nut securing the pipe to the EGR valve - see Chapter 6 for full details if required.

7 While the manifold can be removed with the pulse-air system components attached - unbolt the filter housing and disconnect its vacuum hose if this is to be done - it is easier to remove the pulse-air assembly first, as described in Chapter 6 (see illustration).

7.7 Pulse-air system (sleeve nuts arrowed) need not be removed unless
7.7 Pulse-air system (sleeve nuts arrowed) need not be removed unless required - assembly can be withdrawn with exhaust manifold

8 Unplugging the oxygen sensor electrical connector to avoid straining its wiring, unscrew the nuts to disconnect the exhaust system front downpipe from the manifold (see Chapter 4).

9 Remove the nuts and detach the manifold and gasket (see illustration).

7.9A Unscrew nuts (arrowed) to remove exhaust manifold . . .
7.9A Unscrew nuts (arrowed) to remove exhaust manifold . . .

Take care not
to damage vulnerable components such as the EGR pipe as the manifold assembly is manoeuvred out of the engine compartment.

When removing the manifold with the engine in the vehicle, additional clearance can be obtained by unscrewing the studs from the cylinder head; a female Torx-type socket will be required (see illustration).

7.9B . . . studs can be unscrewed also, if required, to provide additional
7.9B . . . studs can be unscrewed also, if required, to provide additional working space

10 Always fit a new gasket on reassembly, to carefully-cleaned components (see below).

Do not attempt to re-use the original gasket.

Inspection
11 Use a scraper to remove all traces of old gasket material and carbon deposits from the manifold and cylinder head mating surfaces. If the gasket was leaking, have the manifold checked for warpage at an automotive machine shop, and have it resurfaced if necessary.

Caution: When scraping, be very careful not to gouge or scratch the delicate aluminium alloy cylinder head.

12 Provided both mating surfaces are clean and flat, a new gasket will be sufficient to ensure the joint is gas-tight. Do not use any kind of exhaust sealant upstream of the catalytic converter.

13 Note that the downpipe is secured to the manifold by two bolts, with a coil spring, spring seat and self-locking nut on each. On refitting, tighten the nuts until they stop on the bolt shoulders; the pressure of the springs will then suffice to make a leakproof joint (see illustrations).

7.13A Showing exhaust downpipe-tomanifold securing bolts - note coil spring,
7.13A Showing exhaust downpipe-tomanifold securing bolts - note coil spring, and shoulder on bolt

7.13B Renew exhaust system downpipeto-manifold gasket to prevent leaks
7.13B Renew exhaust system downpipeto-manifold gasket to prevent leaks

14 Do not overtighten the nuts to cure a leak - the bolts will shear; renew the gasket and the springs if a leak is found. The bolts themselves are secured by spring clips to the manifold, and can be renewed easily if damaged (see illustration).

7.14 Release spring clip to extract securing bolt from manifold, when
7.14 Release spring clip to extract securing bolt from manifold, when required

Refitting
15 Refitting is the reverse of the removal procedure, noting the following points: (a) Position a new gasket over the cylinder head studs, and fit a new plastic guide sleeve to the stud nearest to the thermostat housing, so that the manifold will be correctly located (see illustration).

7.15 Fit plastic guide sleeve to stud arrowed when refitting exhaust manifold
7.15 Fit plastic guide sleeve to stud arrowed when refitting exhaust manifold

Do not refit the manifold without this sleeve.

(b) Refit the manifold, and finger-tighten the mounting nuts.

(c) Working from the centre out, and in three or four equal steps, tighten the nuts to the torque wrench setting given in the Specifications Section of this Chapter.

(d) Refit the remaining parts in the reverse order of removal. Tighten all fasteners to the specified torque wrench settings.

(e) Refill the cooling system (see Chapter 1).

(f) Run the engine, and check for exhaust leaks. Check the coolant level when fully warmed-up to normal operating temperature.


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