NA timing chain: when to change it and how

The short answer

Officially the chains last the life of the engine, but they don't always. The oil jet that sprays the chain can clog, and the tensioners can break. So if the chains rattle, get them changed. If they have never been changed, it is probably worth getting it done. It costs far less than the damage if one lets go.

This is for the 2.2 NA (Z22SE), which has a timing chain and a separate balancer chain. The 2.0 Turbo has a belt instead: see Turbo cam belt change.

How often

• One owner said the chains were designed for 100,000 miles or ten years, whichever comes first. That is one post, so treat it as a rough guide rather than a Vauxhall figure.
• The same owner advised changing both at 80,000 miles or 8 years. Another owner said 75,000 miles was well due for peace of mind, and another still goes by 60,000.
• Failures reported in the threads include chains breaking at about 57,000 to 67,000 miles. One of those was blamed on an oil pump seizure.
• Age matters as well as miles. One owner pointed out that the chain guides go brittle with age.
• Others stressed that mileage on its own means little. A well-maintained car with 84,000 miles is a better bet than a neglected low-mileage one. Buy on condition and history.
• Regular oil changes matter. Owners suggested a maximum of 5,000 to 10,000 miles between changes. A chain that has had dirty oil will wear faster, whichever kit is fitted.

If you are buying a car and can't show the chains were changed, budget to do it, and use it in your negotiation. See Buyers guide: what to check and ask.

What can go wrong

• Blocked oil jet. Early engines had a single small jet that sprays oil onto the chain. Later engines have a larger one. Either can clog, and a starved chain wears quickly. The nozzle sits behind the timing case. TIS has a separate procedure for replacing it (torque 10 Nm), so if the case is off for a chain job, check the nozzle and replace it at the same time.
• Broken tensioner. A failing tensioner lets the chain go slack and rattle. Owners mentioned an improved tensioner introduced later. TIS says the camshaft chain tensioner should carry a marking, and if yours has none it should be replaced with the current tensioner and a new tensioner rail. One owner described the later type as having a dome on its 32 mm head, which is a single post. If you can see the tensioner (cam cover off), check for the marking.
• Balancer chain. One owner found the balancer chain tensioner had broken down and the chain had stretched badly, with no tension in it, though the cam chain had been fine. That is why many people change both chains together.
• Oil pump failure. Reported as a cause of a chain snapping.

What a failing chain sounds like

• A metallic rattle at cold start, or a loose-chain sound at idle (one owner described it as a chain rotating with no tension in it).
• It isn't always the chain. Hydraulic lifters and a cracked exhaust manifold make similar noises. A manifold rattle tends to disappear within about 15 seconds of starting, as the engine warms.
• How long a rattling chain lasts before it breaks is unknown. One owner said he did not know, which is the reason to act on it. Another changed his at 38,000 miles because of a rattle.
• No rattle doesn't guarantee a healthy chain, so age and history still count.

Cost

These figures are from 2008 to 2013 forum posts, so expect prices to be higher now.

• In 2011 an independent specialist charged £400 all-in for the cam chain, with genuine parts, labour, oil and filter. He charged £350 for a similar job on an Astra or Vectra, and a little more for the VX because it is awkward. The balancer chain was extra.
• In 2008 an owner quoted £400 to £600 at independents. Another gave parts as about £130 for the chain kit. A DIY owner paid about £200 in parts for both chains.
• That job took about 4.5 hours at the specialist, including breaks, and one owner estimated 2.5 hours with no problems.

Doing it yourself

The Vauxhall TIS has full procedures for the Z22SE: Timing Chain, Camshaft, Replace (93 steps), Timing Chain, Balancer Shaft, Replace (97 steps), and shorter ones for the tensioners, the timing case and the oil spray nozzle. The 2011 owner write-up (clam off) fills in the practical detail. Below are the points that matter most, from both. This is not a full procedure, so work from TIS alongside it.

• What TIS has you remove. Even for the camshaft chain alone, TIS takes off the timing case, which means draining the oil, removing the front exhaust pipe, alternator belt and crank pulley, and supporting then lowering the engine so the long timing case bolt clears the chassis member. It also has you release the fuel pressure and move the fuel lines aside, and take off the cam cover. For access, it says the front of the engine is best reached through the right-hand rear wheel arch with the liner out.
• With the clam on or off? The 2011 author took the clam off. Another owner said it can be done with the clam on in about three hours without touching the fuel pipes, gearbox mounts or exhaust. Others said 3 to 4 hours if you move the engine.
• Timing. Set the engine to TDC on cylinder 4, using the mark on the crank pulley. The cams of cylinder 4 point upwards. TIS fits cam locking tool KM-6148, which has positioning bolts that drop into the bores in the cam sprockets, to confirm and hold the cam position. Leave the car in 4th gear and don't move it with the chains off, if you have no tool. The chain has coloured links: the copper one goes to the INT mark on the intake sprocket, and another goes to the EXH mark on the exhaust sprocket. Check the coloured links on your chain before you start. TIS says to secure the chain at the cam sprocket marking with a plastic wedge while you work.
• Check after assembly. After a single turn of the engine the marks no longer line up with the coloured links, so check before you turn it. If they don't line up, refit the chain. At the end, TIS has you rotate the crankshaft 720° (two full turns) back to TDC on cylinder 4 and check the cams with the locking tool again, then remove the tool.
• Cam sprocket bolts. Use new ones. Hold the camshaft by its hexagon with a spanner while you loosen or tighten.
• Upper guide rail. Recut the two threads, coat the bolts with red thread locking compound and torque them to 8 Nm.
• Balancer chain. If you replace the balancer chain, TIS has you take the camshaft chain out as well, so doing both costs little extra labour. The balancer shafts are timed and rotate freely, so don't knock them. The balancer chain has a copper link that goes to the mark on the balancer shaft on the intake side, one link wedged at the balancer sprocket marking, the chain on the coolant pump sprocket, and another link on the mark on the exhaust-side balancer shaft. Fit the guide rails and tensioner rail (10 Nm), then the tensioner, locked with KM-6077, and remove the wedge. As with the cam chain, the marks stop lining up once the engine has turned.
• Oil pump. One owner said the oil pump can be swivelled aside for the cam chain only, but must come off for both chains. TIS doesn't mention moving the oil pump in either procedure, and another owner didn't touch it, so expect your car to differ.
• Oil. TIS drains the oil. One owner said you don't have to for the cam chain alone, but put something over the opening at the bottom of the chain housing, as it goes straight into the sump. One owner dropped a bolt into the sump that way.
• Timing case. Cover the opening in the timing case with a cloth when you remove it, and take the cloth out before you refit it. TIS says to use a new gasket (the 2011 write-up said an undamaged one could be reused), clean the sealing surfaces without damaging them, and fit a new crankshaft front oil seal while it is off. That is cheap insurance against a leak later. TIS uses a special tool for the seal, so expect to improvise.
• Camshaft chain tensioner. Lock the piston before fitting: pull it out of the housing, clamp the square in a vice, and turn it clockwise to lock the internal piston in its last latch position. Then insert it with new oil seals and torque it to 75 Nm. On engines over 48,000 km, release it afterwards by pressing on the tensioner rail or the chain with a blunt tool, such as a rounded assembly lever. TIS warns that skipping this could make the chain jump. On engines under 48,000 km it releases itself when the engine starts. TIS also says to replace an unmarked tensioner with the current part and a new tensioner rail.
• Tensioner only. TIS shows the camshaft chain tensioner can be replaced with just the engine cover, ignition module and cylinder head cover off. If the rattle turns out to be the tensioner, that is a much smaller job than a full chain change. Use new cam cover gaskets, with the seal lips seated in the groove, and torque the cover to 9 Nm.
• Balancer chain tensioner only. This one sits behind the timing case, so the timing case has to come off. The tensioner is held by 2 bolts (10 Nm) and is locked with KM-6077 while you fit it.
• After the job. Refill with oil and check the level. Reconnect the battery and reprogram the volatile memories.

Pitfalls

• Holding the crank pulley. An assistant standing on the brake, with the car in gear, worked for undoing it. A helper is not enough for the final torque. If you rely on the brakes with the wheels off, one owner warned you should refit a wheel bolt into the hub, or the driveshaft can shear the small bolt holding it to the brake disc. Other owners use a flywheel locking tool, a home-made bar bolted to the pulley, or a flat screwdriver through the gap on the exhaust side of the bell housing (a last resort).
• Pulley won't tighten. One owner couldn't get the pulley bolt to hold. The pulley was not sitting square on the crank and the key was soft. It had to come off again. Make sure the pulley is fully seated before you torque the bolt.
• Chewed sprocket bolt. The 2011 write-up says 19 mm for the cam sprocket bolt. An owner found it is actually 18 mm and rounded the intake bolt with a 19 mm socket. Use a 6-point 18 mm.
• Broken guide bolt. One owner sheared the lower bolt of the front top chain guide while removing the chains. It is a stud in the aluminium block. He thought this isn't uncommon. A right-angled drill got the broken part out. Others advised heat to soften thread lock, a good extractor set with left-hand drill bits, and care with welding a nut on, as it can weld the stud to the head. Another owner’s advice in that thread was to remove the bottom end from the car.
• Seized exhaust fixings. If you remove the exhaust, the joints may be seized. One owner’s were, and some sheared. Replace with brass nuts or marine-grade stainless fixings.
• Check the whole job. Before closing up, recheck the coloured links and marks as TIS describes, then turn the engine over by hand to check it spins freely.