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Cylinder head - removal and refitting
In-car engine repair procedures / Cylinder head - removal and refitting


Removal
Note: The following text assumes that the cylinder head will be removed with both inlet and exhaust manifolds attached; this simplifies the procedure, but makes it a bulky and heavy assembly to handle - an engine hoist will be required, to prevent the risk of injury, and to prevent damage to any delicate components as the assembly is removed and refitted. If it is wished first to remove the manifolds, proceed as described in Sections 6 and 7 of this Chapter; amend the following procedure accordingly.

1 Relieve the fuel system pressure (see Chapter 4).

2 With the vehicle parked on firm level ground, open the bonnet and disconnect the battery negative (earth) lead - see Chapter 5, Section 1.

3 Whenever you disconnect any vacuum lines, coolant and emissions hoses, wiring loom connectors, earth straps and fuel lines as part of the following procedure, always label them clearly, so that they can be correctly reassembled.

4 Unplugging the two electrical connectors, disconnecting the vacuum hose (where fitted) and disconnecting the crankcase breather hose from the cylinder head cover, remove the complete air cleaner assembly with the air mass meter, the resonator and the plenum chamber (see Chapter 4).

5 Equalise the pressure in the fuel tank by removing the filler cap, then undo the fuel feed and return lines connecting the engine to the chassis (see Chapter 4). Plug or cap all open fittings.

6 Disconnect the accelerator cable from the throttle linkage as described in Chapter 4 - where fitted, disconnect also the cruise control actuator cable (see Chapter 12). Secure the cable(s) clear of the engine/transmission.

7 Unbolt the power steering high-pressure pipe from the cylinder head rear support plate/engine lifting eye, and from the front support plate/pump bracket. Releasing its wire clip, unplug the power steering pressure switch electrical connector, then unbolt the earth lead from the cylinder head rear support plate/engine lifting eye.

8 Remove the three screws securing the wiring rail to the rear of the manifold.

Releasing its wire clip, unplug the large electrical connector (next to the fuel pressure regulator) to disconnect the engine wiring from the main loom (see illustration).

14.8A Release wire clip to unplug engine wiring loom connector from inlet
14.8A Release wire clip to unplug engine wiring loom connector from inlet manifold

Unplug the
electrical connectors on each side of the ignition coil, and the single connector from beneath the front of the thermostat housing, to disconnect the coil and coolant temperature gauge sender wiring (see illustration).

14.8B Unplug connectors (arrowed) to disconnect ignition coil wiring
14.8B Unplug connectors (arrowed) to disconnect ignition coil wiring

9 Marking or labelling them as they are unplugged, disconnect the vacuum hoses as follows:
(a) One from the rear of the throttle housing (only the one hose - there is no need to disconnect the second hose running to the fuel pressure regulator).

(b) One from the union on the inlet manifolds left-hand end (see illustration).

14.9 Disconnect vacuum hoses (arrowed) as described in text
14.9 Disconnect vacuum hoses (arrowed) as described in text

(c) The braking system vacuum servo unit hose (see Chapter 9 for details).

(d) Disconnect all vacuum hoses from the Exhaust Gas Recirculation system components - one from the EGR valve and two from the EGR pipe. (Note that these last two are of different sizes, as are their pipe stubs, so that they can only be connected the correct way round.) 10 Unbolt both parts of the exhaust manifold heat shield; unclip the coolant hose to allow the upper part to be withdrawn. Either remove the dipstick and tube, or swing them out of the way.

11 Unscrew the single bolt securing the pulse-air filter housing to the engine/ transmission front mounting bracket, then disconnect its vacuum hose.

12 Drain the cooling system (see Chapter 1).

13 Disconnect all coolant hoses from the thermostat housing (see illustration).

14.13 Disconnect all coolant hoses (arrowed) from thermostat housing
14.13 Disconnect all coolant hoses (arrowed) from thermostat housing

14 Unscrew the two nuts to disconnect the exhaust system front downpipe from the manifold (Chapter 4); disconnect the oxygen sensor wiring, so that it is not strained by the weight of the exhaust system.

15 Remove the auxiliary drivebelt (see Chapter 1).

16 Support the weight of the engine/transmission using a trolley jack, with a wooden spacer to prevent damage to the sump.

17 Unscrew the six nuts securing the engine/transmission right-hand mounting bracket, then withdraw the bracket. Unbolt the auxiliary drivebelts idler pulley (see illustration).

14.17 Unbolt auxiliary drivebelt idler pulley
14.17 Unbolt auxiliary drivebelt idler pulley

18 Unbolt the cylinder head front and rear support plates (see illustrations).

14 18A Remove cylinder head front . . .
14 18A Remove cylinder head front . . .

14.18B . . . and rear support plates
14.18B . . . and rear support plates

19 Remove the timing belt and both camshafts (see Sections 10 and 13); if the cylinder head is to be dismantled, withdraw the hydraulic tappets.

20 Remove the timing belt inner shield (see Section 9).

21 Working in the reverse of the sequence shown in illustration 14.32C, slacken the ten cylinder head bolts progressively and by one turn at a time; a Torx key (TX 55 size) will be required. Remove each bolt in turn, and ensure that new replacements are obtained for reassembly; these bolts are subjected to severe stresses and so must be renewed, regardless of their apparent condition, whenever they are disturbed.

22 Lift the cylinder head away; use assistance if possible, as it is a heavy assembly (see illustration). Remove the gasket, noting the two dowels, and discard it.

14.22 Using an engine hoist to lift off the cylinder head complete with
14.22 Using an engine hoist to lift off the cylinder head complete with manifolds

Refitting
23 The mating faces of the cylinder head and cylinder block must be perfectly clean before refitting the head. Use a hard plastic or wood scraper to remove all traces of gasket and carbon; also clean the piston crowns. Take particular care, as the soft aluminium alloy is easily damaged. Also, make sure that the carbon is not allowed to enter the oil and water passages - this is particularly important for the lubrication system, as carbon could block the oil supply to any of the engines components. Using adhesive tape and paper, seal the water, oil and bolt holes in the cylinder block. Clean all the pistons in the same way.

24 Check the mating surfaces of the cylinder block and the cylinder head for nicks, deep scratches and other damage. If slight, they may be removed carefully with a file, but if excessive, machining may be the only alternative to renewal.

25 If warpage of the cylinder head gasket surface is suspected, use a straight edge to check it for distortion. Refer to Part B of this Chapter, Section 7, if necessary.

26 Wipe clean the mating surfaces of the cylinder head and cylinder block. Check that the two locating dowels are in position in the cylinder block, and that all cylinder head bolt holes are free from oil.

27 Position a new gasket over the dowels on the cylinder block surface, so that the TOP/OBEN mark is uppermost, and the tooth (or teeth, according to engine size) protruding from one edge point to the front of the vehicle (see illustration).

14.27 Ensuring protruding tooth (or teeth) A are at front and marking
14.27 Ensuring protruding tooth (or teeth) A are at front and marking B is upwards, locate new cylinder head gasket on dowels C

28 Temporarily refit the crankshaft pulley, and rotate the crankshaft anti-clockwise so that No 1 cylinders piston is lowered to approximately 20 mm before TDC, thus avoiding any risk of valve/piston contact and damage during reassembly.

29 As the cylinder head is such a heavy and awkward assembly to refit with manifolds, it is helpful to make up a pair of guide studs from two 10 mm (thread size) studs approximately 90 mm long, with a screwdriver slot cut in one end - two old cylinder head bolts with their heads cut off would make a good starting point. Screw these guide studs, screwdriver slot upwards to permit removal, into the bolt holes at diagonally-opposite corners of the cylinder block surface (or into those where the locating dowels are fitted, as shown); ensure that approximately 70 mm of stud protrudes above the gasket.

30 Refit the cylinder head, sliding it down the guide studs (if used) and locating it on the dowels (see illustration). Unscrew the guide studs (if used) when the head is in place.

14.30 Refitting cylinder head - note fabricated guide studs (arrowed)
14.30 Refitting cylinder head - note fabricated guide studs (arrowed)

31 Fit the new cylinder head bolts dry (do not oil their threads); carefully enter each into its hole and screw it in, by hand only, until fingertight.

32 Working progressively and in the sequence shown, use first a torque wrench, then an ordinary socket extension bar and an angle gauge, to tighten the cylinder head bolts in the stages given in the Specifications Section of this Chapter (see illustrations).

14.32A Tightening cylinder head bolts (to first and second stages) using
14.32A Tightening cylinder head bolts (to first and second stages) using torque wrench . . .

14.32B . . . and to third stage using angle gauge
14.32B . . . and to third stage using angle gauge

14.32C Cylinder head bolt tightening sequence
14.32C Cylinder head bolt tightening sequence

Note: View from rear of vehicle

Note: Once tightened correctly, following this procedure, the cylinder head bolts do not require check-tightening, and must not be retorqued.

33 Refit the hydraulic tappets (if removed), the camshafts, their oil seals and pulleys (see Sections 10, 11, 12 and 13, as appropriate).

Temporarily refit the crankshaft pulley, and rotate the crankshaft clockwise to return the pulley notches to the position described in paragraph 8 of Section 10.

34 Refit the timing belt and covers, checking the camshaft alignment (valve timing) and setting the timing belt tension, as described in Section 10.

35 The remainder of reassembly is the reverse of the removal procedure, noting the following points:
(a) Tighten all fasteners to the torque wrench settings specified.

(b) When reassembling the engine/transmission right-hand mounting, renew the self-locking nuts, and do not allow the mounting to twist as the middle two of the brackets six nuts are tightened.

(c) Refill the cooling system, and top-up the engine oil.

(d) Check all disturbed joints for signs of oil or coolant leakage, once the engine has been restarted and warmed-up to normal operating temperature.


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