This job is within the capabilities of any reasonably proficient DIY owner. This note is not intended to substitute for a workshop manual but is a reference to draw attention to key aspects of the job which may differ from other engines.
Removal of the head it is fairly straight forward, you’d remove the things you’d expect to. Generally, people leave the intake manifold attached to the head as the underneath bolts holding the manifold to the head are difficult to access. On the VVC models remove the plenum chamber from the manifold.
The most important things to note when removing the head are:
- Set the engine to the cam timing position before releasing the cam belt. This is when the pistons are all halfway up the cylinders – all at the same height. This means that you can rotate the camshafts without fear of the valve hitting the pistons – though you do have to take care that you don’t have both sets of valves open at the same time in any of the cylinders. To identify this position, there is a cam timing mark on the crank pulley. Gain access to this by removing a cover in the RH wheel arch. Sounds a pain, but in fact it is simple!
- Understand that there are TWO sets of timing marks on the crank pulley – one for cam timing, the other for ignition timing. DON’T MIX THEM UP. If you do the result will be expensive!! The ignition timing mark is on the inside flange of the pulley (ie the one nearest to the cam belt cover) and its corresponding marks on the cam belt cover are at 10-11 O’clock. The cam timing mark on the pulley is on the outside flange, and its corresponding mark on the belt cover is at 12 O’clock
- After you have removed the head, DO NOT TURN THE CRANKSHAFT until you have refitted the head! If you do, you may dislodge one or more cylinder liners from its seat, and have to remove and strip the engine to re-seat it. This is why point 1 above is so important.
- It is not necessary to remove the camshaft ladder, or the camshafts. However you will have to remove the camshaft gears in order to allow the head to get past the inner cam belt cover. (In the VVC, there is no need to remove the secondary set of cam gears at the other end of the head.)
- You will have to rotate the camshaft to clear a couple of head bolts. There are some lugs on the camshafts which prevent withdrawal of the head bolts in the timed position. Because the pistons are all halfway down the bore in the timing position, you don’t need to worry about valves hitting them. All you have to watch for is that you don’t get both inlets and exhaust valve on any one cylinder open at the same time. To turn, use a spanner on the camshaft bolt. That way you’ll also have a better feel in case the valves unexpectedly encounter another valve or a piston and should avoid damage. You don’t need to turn the cam back to the timing position until you have the head bolt back in when reassembling … but don’t forget to!!
You will need an E12 socket to undo the head bolts
When reassembling the cam gears it is most important in the non-VVC version to understand that both these gears are the same, and have two slots – one for inlet, the other for exhaust. Ensure that the locating dowel in the camshaft is mated to the correct slot. Oddly enough, the one marked “IN” for the inlet cam, the one marked “EX” for the exhaust cam. Even professionals have mucked this one up and had to remove the head and fit some new valves as a result!
Head bolt torque: Tightening order is as usual starting from the centre and working outwards, alternating either side of the middle.
Step 1: Torque all bolts to 20 Newton-metres.
Step 2: Mark all bolt heads on the edge nearest the main cam belt.
Step 3: Tighten all bolts 180- deg
Step 4: Tighten all bolts another 180 deg.