Timing Belts and Chains
by Pat Goss
In any engine you have to have a way to operate the valves in the top of the engine and that’s done by means of connecting the crank shaft in the bottom of the engine to the cam shaft or cam shafts in the top of the engine. Now back in the day, for many, many, many years this was the method they did that with. It was a very simple timing chain with sprockets such as we see here. But that later went away. And what we saw as a replacement first was a timing belt such as we see here.
Now, timing belts are made of rubber so therefore they’re made of replaceable parts just like the tires on the car. They go bad with time or mileage whichever comes first. Now you have to make sure whatever your owner’s manual tells you, you don’t exceed either the time or the mileage because if one of these goes bad, well it could destroy the engine. Now the thing that we see most frequently, it’s not that the belt actually breaks. You see down here at this bottom sprocket there’s a lot more tension on the teeth because the sprocket is smaller. Well when you start the car, what happens is as the car ages it strips off some of the teeth. We can see this one right here it is trying to come off. It is broken and ready to come off. When that happens, well the crank shaft continues to turn the pistons move up and down, and the valves are static, so the pistons hit the valves you’ve got major damage to your engine.
Alright, but timing belts have pretty much gone away over the last few years. Now we’re back at timing chains, but timing chains now are nothing like the old ones. You see, now because the cams are up on the tops of the heads, you’ve got big long chains. You’ve got multiple chains, and we can’t have them just rolling around in there, so now we have chain guides and chain tensioners and all these different parts that go along with the timing chains. Now the key to all of this is, we don’t want these parts to wear, and some of these guides and tensioners here these are made of plastic and they require a thin film of oil to prevent the plastic from wearing out. So you gotta have good clean oil all the time.
Second thing is that you have hydraulic tensioners like these. Now, as you start the car this piston comes out and it maintains pressure against the timing chains. Well these have little fine oil passages in them. Failure to change the oil, well those oil passages get clogged and then when you start the car the engine rattles, and that rattling is the chain bouncing against these plastic parts and it doesn’t take long before these plastic parts break and you’re looking at a major and I do mean major repair on most engines. So clean oil, the proper viscosity and these parts will last almost forever. And if you have a question or a comment drop me a line right here at MotorWeek.