Timing Chain Replacement
Time = 5-6 hours Task=Relatively Complex
Replacing is not particularily difficult, but you will need at least
the following parts:
- Upper timing cover gasket set 11141721919
- Lower timing cover gasket set 11141721802
- Front profile gasket (NOT the infamous one!) 11141247837
- Rocker cover gasket set (only if the existing ones are old - they will withstand removal while the rubber is soft) 11121721876 profile gasket, 11121721475 spark plug chamber seal - lollipop shape, 3 off 11121721476 spark plug chamber - O shape)
- Timing chain 11311247160
- Crankshaft sprocket 11211247338
- Camshaft sprockets (2 off) 11311721887
- Front crankshaft oil seal 11141439570
- Thermostat housing gasket 11531721172
- Tensioner guide rail 11311727342
- Guide rail 11311247470
- 2-3 litres of phosphour free antifreeze and 2 litres of water
- If your timing chain tensioner is more than 4 years old you should replace it too - 11311743187 with its sealing washer 07119963355
It is also a very opportune time to replace the thermostat and water pump - they are not too expensive and can be bought spuriously (they are the same as the M40 engine). You might as well flush the radiator and coolant system too.
The job is a straight-forward strip and replace. Here are the main steps:
- Remove the fan shroud and the thermo-viscous fan as described in the Maintenance Section.
- Remove the spark plug cover. Unplug the leads - mark them if necessary. Loosen the two 10mm nuts holding the metal spark plug lead guide to the rocker cover. Using a screwdriver, lift out the plastic lead tray. Tuck the leads and metal guide out of they way (down by the exhaust manifold).
- Remove the rocker cover (15 off 11mm bolts). Note the 2 shorter bolts are in the centre and the breather hose.
- Rotate the crank so the cam lobes for cylinder 1 (front) are roughly pointing upwards.
- Put the car in Neutral.
- Loosen the crankshaft bolt (22mm). It is VERY tight - ~230 ftlbs, but needs a shock to release it. Forget a rattle gun (not strong enough) or a breaker bar (you will slip the clutch first). So, remove the airbox (2 off 10mm nuts and a jubilee clip). Put a power bar (of suitable length) vertically upwards on the pulley bolt and a block of wood on the LH chassis arm. Crank the starter motor momentarily so that the bar rotates 90 degrees into the block of wood! 3-4 goes at this will usually release the bolt. It is a normal right-hand thread. Note that BMW uses a tool which bolts on in place of the vibration damper (6 bolts). The tool is locked against the chassis arm and a breaker bar is then used.
- Remove the water pump and thermostat housing as described back in the MaintenanceSection.
- Remove the crank and camshaft sensor wiring, trunking and sensors. The sensors are held in with 5mm allen key bolts and the trunking by one 10mm bolt on each of the timing covers.
- If you don't have the tool, remove the small access plug on the engine side of the bellhousing, just below the starter motor. Get an 8mm drill bit or a M8 bolt at least 45mm long. Put it through the hole and rotate the crank back and forth slightly until it pops into the corresponding hole in the flywheel. This is TDC, cylinder 1.
- To ensure realignment it is imperative that the squares at the rear of the cams are horizontally in line. If you have the camshaft holding tool, fit it now.
- The crankshaft vibration damper is bolted on with 6 off 13mm bolts and simply pulls off the crank pulley - note its locating pin.
- Keeping the flywheel still, unscrew the crank bolt a couple of turns. Using a pullers, extract the crank pulley as far as possible. Remove the crank bolt and pulley.
- Unbolt the upper (10 off 10mm) and then the lower timing covers (a few 10mm and 3 off 13mm). Keep an eye out for the locating dowels as you take off the lower timing cover as they might fall out. Also note that 3 of the 10mm bolts are shorter - they correspond to indents in the cover's shape.
- Release the chain tensioner (19mm) and place it in a clean area if it is to be used again. Watch out for a dribble of oil coming out.
- Tippex the crank against the block and the cam sprockets against the cylinder head as a precaution. Beware that the combustion chamber is an interferance design (the valves can strike the piston).
- Remove the top and bottom chain guides (2 off 5mm allen key each). They are unlikely to be worn but check just in case.
- Note the angular position of the cam sprocket bolts relative to their slots (they may be marked), as the new sprockets will need to go back close to the same place. Remove the cam sprockets (4 off 10mm each), lift off the timing chain and remove the crank sprocket with the pullers (although it can be wiggled off).
- Remove and replace the two long side guides (5 mm allen key).
- Clean off the old gaskets from the the timing case and the covers. Put a rag at the bottom of the timing case to prevent bits of gasket from falling into the sump.
- Install the new crank sprocket, chain and cam sprockets. The cam bolts are 15 ftlbs - put a little thread lock on them first.
- Double check that the squares at the rear of the cams are horizontally in line and the TDC has been held. There shoud be 15 rivets (inclusive) of the chain from arrow to arrow on each cam.
- Install the top and bottom chain guides.
- Install the chain tensioner. If you are reinstalling the old one, you may need to compress it in a bench vice (it should click) before reinstalling it - but you may be able to compress and turn it at the same time with a ratchet and socket (I did!).
- Remove the old crank oil seal from the lower timing cover by tapping it out from the rear. Apply some engine oil to the inner and outer diameters of the new seal. Using a large socket or a flat piece of wood, evenly tap it in until it seats evenly. Take care not the damage the inner diameter.
- Apply the new gaskets to the upper and lower timing covers. Use some instant gasket to keep them in place.
- Bolt in the lower cover. Put the profile gasket in place. Apply some instant gasket on the upper and lower join. Install the upper cover. Watch your torque values - the timing case bolts are torqued to 9 ft-lbs.
- Reinstall the crank pulley, spacer and bolt. Torque to 230 ftlbs (or as near as you can get) by putting the car in 5th and having an assistant press the brakes.
- Now go back and double recheck that the cams are still square with TDC pinned at the flywheel. Loosen the sprockets and adjust if not.
- Remove the engine oil (19mm plug). Put the plug back in.
- Dribble some fresh engine oil down both sides of the timing chain and along its top.
- Install the rocker cover, the spark plug guides, the spark plug leads and the cover. The rocker cover bolts are torqued to 9 ft-lbs.
- Install the water pump and thermostat as described back in the Maintenance section.
- Check the o-ring condition on the camshaft sensor. It is 18x2. Install the two sensors and brackets.
- Top up the engine oil.
- Reinstall the AFM if you removed it earlier
- Start the engine and bring it to 2500rpm for ~30 seconds to release the timing chain tensioner (if new).
- Bleed the coolant system by leaving both the radiator cap and bleed screw open during the heat up process. Don't forget to put the heater on full heat inside car.
- Check for any water or oil leaks.
Note: If the cam timing is incorrect, the engine will "diesel". Reference the crank TDC again and check that the camshaft timing marks are upwards (just remove the rocker cover). Then check that the squares on each cam are level. Undo the relevant sprocket and move it one tooth in the necessary direction.