Martynn Randall is technical editor at Haynes and has been with us for approaching 30 years. He's written more than 60 Haynes publications and has owned more than 85 cars and 60 motorbikes... so far!
Timing. When it’s good, things tend to go well, everything’s in harmony, and difficult stuff just seems to happen more easily – think of stepping forward and knocking that little red ball over the boundary for a six, listening to an orchestra when everyone is fully in the moment, or everyone working slickly and smoothly on a factory production line. It’s all in the timing.
So that's the good. But there's also often the chance of bad timing, when things happen all at the wrong time, and mayhem ensues. Think Keystone cops, getting bowled for a duck, Manchester United’s back line.
And of course, there’s the ugly, when bad timing turns to expensive carnage. For example, the timing belt is arguably the most important component in your car’s engine, because without it, lots of expensive bits of metal will start coming together when they should really be kept apart.
This is why it’s essential that the timing belt is kept in as good condition as possible, which is why I’m even more incredulous that someone came up with the idea of having a timing belt run through a bath of oil inside the engine.
This is a comparatively recent phenomenon, and was begun by Ford with its 1.8-litre TDCi diesel engine of 2007. However, other manufacturers, including Audi, Citroën, Peugeot, Toyota and Volkswagen, followed, while Ford continued with the design in its popular EcoBoost turbocharged petrol motors and EcoBlue diesels.
The good things about wet timing belts
The theory goes that having a timing belt running through a bath of oil means that the belt is constantly lubricated, which should both reduce the noise it makes, and extend its life.
Efficiency is the reason for the invention of the wet belt. Back in the early 2000s, car makers were all looking for ways to make their engines use less fuel and emit less CO2, and Ford worked out that lubricating the timing belt was a good way to achieve that aim. A secondary benefit was that the life of the belt was expected to be extended because it was subject to less friction.
On top of that, a timing belt tends to get hot when working at high speeds, and the oil helps to cool it, again helping to extend the belt’s longevity. At least, that’s the plan.
The bad things about wet cambelts
I have personal experience of wet belts, because I fitted a wet-belt conversion kit to my Norton Commando back in the days of black-and-white televisions and Pathé News. After about 800 miles, it shredded all of the teeth on the belt as I was halfway round the Isle of Man TT course. That was ‘fun’.
Anyway, as everyone of a certain age will attest, things start to deteriorate over time – and your engine’s timing belt is no exception. That’s why there are strict guidelines regarding when you should change it, and at what mileage. However, that same ‘degrading over time’ annoyance also happens to the oil in which the timing belt is luxuriating. The oil becomes contaminated with soot and other impurities, which can cause the belt to become worn ahead of schedule.
That’s bad enough, but when the belt wears, bits can break off and then clog up the engine oil lines and the oil filter. Obviously, this then means that other crucial areas inside the motor then suffer from oil starvation, and premature wear, raising the vehicle’s CO2 output and thirst for fuel. And that’s exactly what the wet belt was designed to avoid in the first place.
With a wet belt, you also need to keep an even closer eye on your engine’s oil level, because any lowering of the level brings a corresponding reduction in lubrication of the belt.
So, the way to avoid damage to the belt is not only to keep on top of the oil level, but also to change the belt regularly, which is precisely the point at which you’ll discover that changing a wet belt is not the work of a moment. In fact, it takes quite a few moments – moments that can extend into days (note the plural here!). It’s a complicated procedure.
This is something that Haynes reader Jamie Miller knows all about. We recently featured him in our ‘Your repairs’ section, because he started to change the belt on his Ford B-Max on a Thursday, and completed it on the Sunday afternoon. And he used the manual for the equivalent Ford Fiesta to help him do it.
Does my car have a wet cambelt?
It’s pretty easy to tell. On a dry-belt engine, the timing gear is attached to the end of the engine. However, with a wet-belt motor, the timing gear is entirely enclosed within the engine, because it needs to be sealed in to keep the oil in with it.
This, however, also means that much more dismantling is required when the time comes to swap the belt, and sometimes special tools will be needed. That’s why professional workshops charge well into four figures to carry out the job.
Verdict
Yes, a wet timing belt requires much more time and effort to change, but the reality is that with the sheer number of engines out there that use them, we’re stuck with them for the time being. So, unless you want to shell out an eye-watering sum to have someone replace it for you, it’s best to do just as Jamie did, and set aside a few days, invest in the Haynes manual for your car, shell out for a pallet of Tunnock’s Caramel Wafers and teabags, then set to work.
At least you’re only ever likely to have to do it once (maybe twice) in the life of your car.