Car Care: Belt v Chain debate resumes
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We have discussed the merits of owning vehicles with engines fitted with either a rubber cambelt or a steel chain in past Driven articles, but after receiving an email from a regular Driven reader and one very unhappy owner, we decided to revisit the subject.
Our reader owns a 2009 V6 Holden VE Sportwagon that has travelled 148,000km and was recently quoted $3500 to have the engine timing chains replaced. The job ended up costing a little less than quoted, which was a welcome relief.
The word “forever” is an interesting one when we talk about the life of a motor vehicle. Most passenger car manufacturers will say the life of a motor vehicle from their perspective is around 10 years or, probably more importantly, around 200,000km. After that, it can all come down to a bit of good or bad luck.
And as we all know, there are many good news stories of vehicles that have travelled well beyond those figures and given owners little trouble.
Back to the belt versus chain. What do they do and why are they so important?
The majority of internal combustion engines have two main components that other parts either connect to, or rely on, to initially start and to keep the engine running. One is the crankshaft and the other is the camshaft.
The crankshaft controls the up and downward movement of the pistons while the camshaft controls the opening and closing of the inlet and exhaust valves.
For the engine to run at all, both shafts need to synchronise with each other, and are therefore, connected by a chain or belt.
When a piston heads towards the top of its stroke, a valve will open just above it and while tolerances run very close, the intention is they stay completely separated from each other. That is until there is a failure of the connecting belt or chain. And when that happens, the consequences are severe. In a worst case scenario, the engine can be pretty much totally destroyed.
To help stop this happening cambelts have a recommended replacement period which is usually around five years or 100,000km (whichever comes first).
In theory, once the belt is replaced, there is no need to worry about it again for some time. Replacement is also often much cheaper than a chain-driven engine because the belt sits outside the main internals of the engine, so there is less labour involved to remove and replace.
Chains, on the other hand, have no recommended replacement period. But that doesn’t mean they last forever. It usually means they will give some warning of stretch and wear before they fail totally. That warning can come by way of an engine rattle or the dash warning light coming on to alert drivers to a problem.
Because the chain(s) relies on lubrication to help prevent wear, it is placed in the bowels of the engine and therefore replacement is far more involved and usually a lot more costly than for the rubber belt.
The big swing in recent years is to fit chains rather than belts to petrol engines. There are several reasons for this change. Oil and chain quality has improved, which means replacement periods can potentially go beyond that 10-year/200,000km manufacturer’s lifespan, meaning owners have reduced routine servicing costs over that time.
This is where owner responsibility comes into play along with workshops that use good-quality oil or stay with manufacturer’s recommendations long after warranty periods have expired.
I have seen near-new engines totally destroyed because of a high buildup of sludge because of the lack of regular servicing. The sludge buildup can be so bad it blocks oil galleries, which in turn can cause the camshaft to eventually seize and instantly snap the cambelt. Or in other cases, timing chains that have worn prematurely because of poor service histories and/or contaminated oil.
So chain v belt on older vehicles — which is best?
There is no right or wrong answer.
In one scenario owners are given clear guidelines of when to replace cambelts to help avoid engine damage, while on the other hand, worn out timing chains can cost significantly more to replace when they do eventually wear out.
Regular servicing definitely helps, but you can also be one of those unlucky owners if you purchase an older vehicle with a high odometer reading and with a poor past service history; especially if it’s a chain-driven engine.
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